Yr 9 Chemical Reactions Sg

Project ManagementExecutive Director: Professor Denis Goodrum, FACE (Australian Academy of Science)Director of Curriculum Development: Jef ByrneDirector of Professional Learning and Strategic Development: Dr Kerrie WildeWeb and Digital Co-ordinator: Dr Jen LiuAdministrative Coordinator: Katie RyanAdministrative Officer: Kathy Hamilton

This resource was written by: Dr Brenda Grieve and Dr Kerrie Wilde.

Science by Doing would like to thank Spinks and Suns for the design and development of this resource.

Funding Acknowledgement

Science by Doing is supported by the Australian Government.

DisclaimerThe views expressed herein do not necessarily represent the views of the Australian Government, Department of Education or Education Services Australia.

These materials are intended for education and training only. Every effort is made to ensure the accuracy of the information presented in these materials. We do not assume liability for the accuracy or completeness of the information contained within. The Australian Academy of Science accepts no responsibility for any loss or damage whatsoever suffered as a result of direct or indirect use or application of any of these training materials.

This unit incorporates a number of chemicals and chemical processes for experimental and investigative purposes. The appropriate and applicable risk assessment and policies should be implemented by a suitably trained teacher on each occasion, as relevant to each school’s standards, teaching environment and context. Teacher demonstrations should only be undertaken by a suitably qualified and trained teacher following a full risk assessment and safety analysis.

© Australian Academy of Science, 2015

• You may freely use this resource for non-commercial educational purposes but please acknowledge the resource and the Australian Academy of Science as the source. Please note there are third party items in this resource that are outlined. To use these items other than in this resource you must obtain permission from the third party owners.

• Under no circumstances may copies be sold in any form.

ISBN 978-0-85847-369-0-376-8 Published by the Australian Academy of Science GPO Box 783 Canberra ACT 2601 Telephone: 02 6201 9400 Fax: 02 6201 9494 www.science.org.au

http://www.science.org.au/

1

CONTENTSUnit map 2

The periodic table of elements 3

PART 1: IT'S ELEMENTARY 4-15Activity 1.1 What’s the matter? 5Activity 1.2 Atoms matter 7Activity 1.3 Atomic structure 9Activity 1.4 What makes chemicals different? 11Activity 1.5 Isotopes 15

PART 2: REACTIONS HAPPEN 16-34Activity 2.1 What is a chemical reaction? 17Activity 2.2 Conservation of mass 19Activity 2.3 Ionic compounds 21Activity 2.4 Writing chemical formulae 25Activity 2.5 Sharing electrons 26Activity 2.6 It's falling apart 29Activity 2.7 Reactions in solution 31Activity 2.8 Chemicals revised 34

PART 3: ENERGY FROM THE NUCLEUS 35-44Activity 3.1 What is radioactivity? 36Activity 3.2 Researching radioactivity 37Activity 3.3 Detecting radioactivity 38Activity 3.4 How long does it last? 40Activity 3.5 Nuclear energy 42Activity 3.6 The future 43

PART 4: ENERGY AND CHANGE 45-55Activity 4.1 What is energy? 46Activity 4.2 Hot and cold 47Activity 4.3 Combustion 49Activity 4.4 Reactions in nature 51Activity 4.5 Industrial chemistry 54

PART 5: ACIDS AND BASES 56-71Activity 5.1 Acid or base? 57Activity 5.2 Indicators 59Activity 5.3 The pH scale 61Activity 5.4 Neutralisation 64Activity 5.5 Acids and metals 66Activity 5.6 Acids and carbonates 67Activity 5.7 Acids and bases everywhere 68Activity 5.8 Are you a chemist? 70

Glossary 72

Icon

Meaning Digital interactive Hands-on inquiry Classroom activity Notebooking Discussion

IT’S ELEMENTARY

PART 1 PART 2 PART 3 PART 4 PART 5ENERGY

FROM THE NUCLEUS

REACTIONS HAPPEN

ENERGY AND CHANGE

ACIDS AND BASES

PART 1 PART 2 PART 3 PART 4 PART 5

2

66

Dy68

Er

TABLE OF THE ELEMENTS

58

CeCerium 140.116

69

TmThulium 168.934

70

YbYtterbium 173.054

101

MdMendelevium

[258]

102

NoNobelium

[259]

71

LuLutetium 174.967

103

LrLawrencium

[262]

90

ThThorium 232.038

59

PrPraseodymium

140.908

60

NdNeodymium

144.242

91

PaProtactinium

231.036

92

UUranium 238.029

61

PmPromethium

[145]

62

SmSamarium

150.36

93

NpNeptunium

[237]

94

PuPlutonium

[244]

63

EuEuropium 151.964

64

GdGadolinium

157.25

95

AmAmericium

[243]

96

CmCurium

[247]

65

TbTerbium 158.925

66

DyDysprosium

162.50

97

BkBerkelium

[247]

98

CfCalifornium

[251]

67

HoHolmium 164.930

68

ErErbium 167.259

99

EsEinsteinium

[252]

100

FmMermium

[257]

1

HHydrogen

1.008

3

LiLithium

6.94

4

BeBeryllium

9.012

11

NaSodium 22.990

12

MgMagnesium

24.305

19

KPotassium

39.098

20

CaCalcium 40.078

37

RbRubidium

84.468

38

SrStrontium

87.62

55

CsCesium 132.905

5

BBoron 10.81

13

AlAluminum

26.982

31

GaGallium 69.723

49

InIndium 114.818

81

TlThallium 204.38

6

CCarbon 12.011

14

SiSilicon 28.085

32

GeGermanium

72.630

50

SnTin

118.71

82

PbLead 207.2

7

NNitrogen 14.007

15

PPhosphorus

30.974

33

AsArsenic 74.922

51

SbAntimony 121.760

83

BiBismuth 208.980

8

OOxygen 15.999

16

SSulfur 32.06

34

SeSelenium

78.971

52

TeTellurium

127.6

84

PoPolonium

[209]

9

FFluorine 18.998

17

ClChlorine

35.45

35

BrBromine 79.904

53

IIodine

126.904

85

AtAstatine

[210]

10

NeNeon

20.180

2

HeHelium 4.003

18

ArArgon 39.948

36

KrKrypton 83.798

54

XeXenon

131.293

86

RnRadon [222]

56

BaBarium 137.327

87

FrFrancium

[223]

88

RaRadium

[226]

21

ScScandium

44.956

22

TiTitanium 47.867

39

YYttrium 88.906

40

ZrZirconium

91.224

57

LaLanthanum

138.905

72

HfHafnium 178.49

89

AcActinium

[227]

104

RfRutherfordium

[267]

23

VVanadium

50.942

24

CrChromium

51.996

41

NbNiobium 92.906

42

MoMolybdenum

95.95

73

TaTantalum 180.948

74

WTungsten

183.84

105

DbDubnium

[268]

106

SgSeaborgium

[269]

25

MnManganese

54.938

26

FeIron

55.845

43

TcTechnetium

[98]

44

RuRuthenium

101.07

75

ReRhenium 186.207

76

OsOsmium 190.23

107

BhBohrium

[270]

108

HsHassium

[269]

27

CoCobalt 58.933

28

NiNickel 58.693

45

RhRhodium 102.906

46

PdPalladium

106.42

77

IrIridium 192.217

78

PtPlatinum 195.084

109

MtMeitnerium

[278]

110

DsDarmstadtium

[281]

29

CuCopper 63.546

30

ZnZinc 65.38

47

AgSilver

107.868

48

CdCadmium 112.414

79

AuGold

196.967

80

HgMercury 200.592

111

RgRoentgenium

[280]

112

CnCopernicium

[285]

113

UutUnuntrium

[286]

114

FlFlerovium

[289]

115

UupUnunpentium

[289]

116

LvLivermortium

[293]

117

UusUnunseptium

[294]

118

UuoUnunoctium

[294]

6

C15

P53

I53

I8

O

metalloid non-metal basic metal halogen noble

gas lanthanide actinide transition metal

alkaline earth metal

alkali metal

THE

3CHEMICAL REACTIONS PERIODIC TABLE

PART 1: IT'S ELEMENTARYActivity 1.1 What’s the matter?Activity 1.2 Atoms matterActivity 1.3 Atomic structureActivity 1.4 What makes chemicals different?Activity 1.5 Isotopes

4

PART

1CHEMICAL REACTIONS PART 1

PLAY

to revise and refresh your chemistry

knowledge.

RULES: Your teacher will

place a sticker on your

forehead with a mystery

chemistry word. No peeking!

In your group, take turns to

ask Yes/No questions and

deduce what is on your

sticker. If you get a No

response, move onto the

next person.

Am I a gas?

Am I in the periodic table?

YES!Ha!

NO!

Am I something from

the lab?

Am I the smallest part of

matter?

Am I ductile?

hmmm I mean malleable and

shiny?

HINT: Use your knowledge of elements and their properties, as well as chemistry apparatus. What is the best way to group or classify these chemistry terms?

HYDROGEN

SPATULA

BUNSEN BURNER

WHAT IS THE MATTER?

5CHEMICAL REACTIONS PART 1 IT'S ELEMENTARY

ACTIVITY TYPE

ACTIVITY 1.1 WHAT’S THE MATTER?

Before you go to the digital resource PART 1: IT'S ELEMENTARY familiarise yourself with the key navigation features.

HOME

provides easy navigation to all of the different sections.

NOTEBOOK PROMPTS

assist you to share your ideas and understandings.

These symbols indicate discussion and notebooking.

PIN ICONS

provide the navigation for each particular section.

What do you already know about matter and elements? Click here to go to the digital resource and open Activity 1.1 to complete the Chemistry Revision Quiz.

HINTS

focus your inquiry and provide questions to help you connect your ideas.

6

ACTIVITY 1.1 WHAT’S THE MATTER? CONTINUED

CHEMICAL REACTIONS PART 1 IT'S ELEMENTARY

http://www.sciencebydoing.edu.au/curriculum/student/yr9/reactions/digital/act1/act11.html

Democritus (460 BCE)

Democritus was one of the first to describe atoms. Was he an artist, scientist, philosopher or all three?According to Democritus, which of the atoms below

would be air, metal, water or salt?

"Halve a piece of paper once, then twice." How many halves will you make before you can make no more? Does it become impossible at some point?Who has the smallest piece?How small is it?Around 460 BC, Democritus asked similar questions and deduced that the smallest and most basic matter particles were "atoms", named after the Greek word "atomos", for "indivisible".

How small is small?I propose atoms look and feel like

the substance they form.

slip

pERY

SMOO

TH

SHARP

SOLID

STRONG

LIGH

T

WHIRLIN

G

The main points of Democritus’ theory were:• Everything was composed

of "atoms", which were indivisible and indestructible.

• There were an infinite number of atoms, and kinds of atoms, which differed in shape and size.

• The look and texture of individual atoms reflected the object. For example, water was made up of smooth and slippery atoms.

• Atoms attached to each other with hooks and eyes, balls and sockets.

• Between atoms was empty space.

• Atoms are always in motion and always would be in motion.

• The larger the atom, the heavier it is.

Hooks and eyes … balls and

sockets?How else?

How would they combine?

TIMELINE

DEMOCRITUS

7

ACTIVITY TYPE

ACTIVITY 1.2 ATOMS MATTER


Dalton calculated the mass of different atoms and gave them symbols.

ELEMENTS

The Democritus atomic model is

worthless! I propose all matter is made of four elements - earth, air,

fire and water.

Aristotle (384-322 BCE), an influential Greek philosopher and mathematician, did not agree with

Democritus.

John Dalton (1766-1844) proposed his atomic theory based on experimental results with chemicals, in which he measured the

amounts of elements that combined to form compounds.Was Dalton a mathematician, scientist, philosopher or teacher?

Why were the theories of Aristotle and his peers accepted

for so long?

Chemical reactions occur

when atoms combine, separate or are

rearranged.

spherical Dalton atom

Dalton's molecules

Click here to go to the digital resource Activity 1.2 and learn more before completing the summary timeline in your Notebook.

All atoms of one element are

alike, but differ from atoms of all other

elements.

All matter is composed

of tiny indivisible particles called

atoms.

Compounds form when atoms combine in simple

whole number ratios.

I wonder what is

inside the atom?’

‘Why do electrons

keep moving?’

Aristotle (380 BC) Dalton (1808)

. . .ABOUT 80 years later... . . .2000 years later, in 1808

How did Dalton's theory differ

from that of Democritus? Can you think of an experiment or

activity which supports Dalton?

ARISTOTLE

DALTON

ACTIVITY 1.2 ATOMS MATTER CONTINUED



Atoms are so small, we cannot see them.

How small are they and what’s inside?

SPLITTING THE ATOM

Teacher demonstration

1. Describe what you observed during the demonstration.

2. How does this demonstration provide evidence for Thomson’s model of the atom?

3. What particles are being removed from the atoms? What evidence is there for this?

4. What is left behind and what charge would it have?

5. What was the main application of the cathode ray tube that affected all our lives?

The accepted model of the atom is based on the Rutherford/Bohr model:• The atom consists of a small,

dense nucleus containing protons and neutrons.

• Electrons orbit in energy levels in the space around the nucleus.

• In a neutral atom, the number of PROTONS equals the number of ELECTRONS.

• The number of NEUTRONS varies, but usually equals the number of protons.

The smallest atom, hydrogen, has a diameter of 50 picometres (pm). A larger

atom, such as lead, has a diameter of about 360 pm.

That’s small!There are 1,000,000,000,000

atoms in a metre.

9

ACTIVITY 1.3 ATOMIC STRUCTURE

ACTIVITY TYPE


6 protons + 6 neutrons

energy levels

Consider the symbolic representation of the carbon atom shown below: what do you notice about its

smaller parts and their arrangement?

Click here to go to the digital resource

Activity 1.3 and learn more about atoms and

their structure.

+–

electron

proton

neutron

+ +

++

–

–

– –

–

–

Carbon atom

Scientists use special terms to describe the structure of

each element:

What to do:1. Using the carbon atom as a guide,

use symbolic representation to show the atomic structure for nitrogen and oxygen. What did you notice about the number of protons, neutrons and electrons?

2. Using your periodic table and the information on this page, can you name these two mystery elements?

The "atomic mass" is the number of protons plus the number of neutrons in the nucleus.

The "atomic number" is the number of protons in the nucleus.

HINT: one is a metal, and

the other is a non-metal.

–

–

–+++

–

–

– –

–––

––

+

++

+

++

+++

10

ACTIVITY 1.3 ATOMIC STRUCTURE CONTINUED



HAVE YOU GOT YOUR LAB COAT AND SAFETY GOGGLES ON? HAIR TIED BACK AND ENCLOSED

SHOES?

WHEN YOU HANDLE CHEMICALS YOU NEED TO ASSESS RISKS AND TAKE PRECAUTIONS.

REVISE LAB SAFETY WITH YOUR TEACHER AND FAMILIARISE YOURSELF WITH CHEMICAL SAFETY WARNINGS. KEEP AN EYE OUT FOR THIS SIGN AS

YOU PROGRESS THROUGH THE UNIT.

REMEMBER LAB SAFETY STARTS WITH YOU! What to do:

What is a risk assessment? How do we know which chemicals are safe to use, and safe to mix?

Discuss with your teacher how

to conduct a risk assessment and identify safety concerns for individual chemicals.

Write a risk assessment for the laboratory task "What’s on the shelf?".

What do we mean by "lab safety starts with you?"

Discuss the safety rules for your lab.

Which are the most important?

Why?

ACTIVITY TYPE

11

ACTIVITY 1.4 WHAT MAKES CHEMICALS DIFFERENT?


What to use:Each PAIR will require:

• periodic table• material safety and data sheets

(MSDS)• Science by Doing Notebook• safety glasses.

What to do:Step 1Observe the displayed laboratory chemicals. Look closely at each substance and the information provided. Are any two similar? Do not open the containers.

Step 2As you observe each chemical, complete a table similar to the one shown, recording the name, formula (and elements present) and description. Are there any safety warnings?

Step 3In pairs, classify and group the chemicals into smaller groups of perhaps three to four.

Step 4Your teacher will provide a mystery chemical. Don’t remove the lid. What do you think it is?

Discussion:1. What properties did you use to

group the chemicals?

2. Share your results with the class. Did the approaches used to group elements and identify the mystery sample vary?

3. Can you group the chemicals into elements and compounds? What is the property difference between these two groups?

Elements contain one type of atom. How many elements can you recall from the periodic table? Draw the atomic configuration for three of them.Compounds contain two or more different elements. Write down three examples and name the individual elements which form this compound. Can you find the elements in the periodic table?

HINT: refer to the periodic table

and safety sheets.

WHAT'S ON THE SHELF?

Substance name

Chemical formula State Description Safety

hydrochloric acid HCl (hydrogen and chlorine) aqueous clear solution

acidic, so can burn you – careful with eyes and skin

lead foil Pb solid grey shiny flexible sheets toxic if swallowed

potassium permanganate

KMnO4 (potassium + manganese + oxygen)

solid purple crystals

shouldn’t contact skin – skin and eye irritant

1

HHydrogen

1.008

3

LiLithium

6.94

4

BeBeryllium

9.012

11

NaSodium 22.990

12

MgMagnesium

24.305

19

KPotassium

39.098

20

CaCalcium 40.078

37

RbRubidium

84.468

38

SrStrontium

87.62

55

CsCesium 132.905

5

BBoron 10.81

13

AlAluminum

26.982

31

GaGallium 69.723

49

InIndium 114.818

81

TlThallium 204.38

6

CCarbon 12.011

14

SiSilicon 28.085

32

GeGermanium

72.630

50

SnTin

118.71

82

PbLead 207.2

7

NNitrogen 14.007

15

PPhosphorus

30.974

33

AsArsenic 74.922

51

SbAntimony 121.760

83

BiBismuth 208.980

8

OOxygen 15.999

16

SSulfur 32.06

34

SeSelenium

78.971

52

TeTellurium

127.6

84

PoPolonium

[209]

9

FFluorine 18.998

17

ClChlorine

35.45

35

BrBromine 79.904

53

IIodine

126.904

85

AtAstatine

[210]

10

NeNeon

20.180

2

HeHelium 4.003

18

ArArgon 39.948

36

KrKrypton 83.798

54

XeXenon

131.293

86

RnRadon [222]

56

BaBarium 137.327

87

FrFrancium

[223]

88

RaRadium

[226]

21

ScScandium

44.956

22

TiTitanium 47.867

39

YYttrium 88.906

40

ZrZirconium

91.224

57

LaLanthanum

138.905

72

HfHafnium 178.49

89

AcActinium

[227]

104

RfRutherfordium

[267]

23

VVanadium

50.942

24

CrChromium

51.996

41

NbNiobium 92.906

42

MoMolybdenum

95.95

73

TaTantalum 180.948

74

WTungsten

183.84

105

DbDubnium

[268]

106

SgSeaborgium

[269]

25

MnManganese

54.938

26

FeIron

55.845

43

TcTechnetium

[98]

44

RuRuthenium

101.07

75

ReRhenium 186.207

76

OsOsmium 190.23

107

BhBohrium

[270]

108

HsHassium

[269]

27

CoCobalt 58.933

28

NiNickel 58.693

45

RhRhodium 102.906

46

PdPalladium

106.42

77

IrIridium 192.217

78

PtPlatinum 195.084

109

MtMeitnerium

[278]

110

DsDarmstadtium

[281]

29

CuCopper 63.546

30

ZnZinc 65.38

47

AgSilver

107.868

48

CdCadmium 112.414

79

AuGold

196.967

80

HgMercury 200.592

111

RgRoentgenium

[280]

112

CnCopernicium

[285]

113

UutUnuntrium

[286]

114

FlFlerovium

[289]

115

UupUnunpentium

[289]

116

LvLivermortium

[293]

117

UusUnunseptium

[294]

118

UuoUnunoctium

[294]

The periodic table arranges elements in order of atomic

number.

How do neighbouring

elements differ? Do they look similar?

Elements exist in three states at room temperature. What are they? What is required for them to change state?

Can you recall the descriptive properties of metals? Identify two and give examples.

Consider the water compound. What makes it different to its element components?Describe the element components of four other compounds you are familiar with.

+H +H-O

ACTIVITY 1.4 WHAT MAKES CHEMICALS DIFFERENT? CONTINUED


58

CeCerium 140.116

69

TmThulium 168.934

70

YbYtterbium 173.054

101

MdMendelevium

[258]

102

NoNobelium

[259]

71

LuLutetium 174.967

103

LrLawrencium

[262]

90

ThThorium 232.038

59

PrPraseodymium

140.908

60

NdNeodymium

144.242

91

PaProtactinium

231.036

92

UUranium 238.029

61

PmPromethium

[145]

62

SmSamarium

150.36

93

NpNeptunium

[237]

94

PuPlutonium

[244]

63

EuEuropium 151.964

64

GdGadolinium

157.25

95

AmAmericium

[243]

96

CmCurium

[247]

65

TbTerbium 158.925

66

DyDysprosium

162.50

97

BkBerkelium

[247]

98

CfCalifornium

[251]

67

HoHolmium 164.930

68

ErErbium 167.259

99

EsEinsteinium

[252]

100

FmMermium

[257]

1

HHydrogen

1.008

3

LiLithium

6.94

4

BeBeryllium

9.012

11

NaSodium 22.990

12

MgMagnesium

24.305

19

KPotassium

39.098

20

CaCalcium 40.078

37

RbRubidium

84.468

38

SrStrontium

87.62

55

CsCesium 132.905

5

BBoron 10.81

13

AlAluminum

26.982

31

GaGallium 69.723

49

InIndium 114.818

81

TlThallium 204.38

6

CCarbon 12.011

14

SiSilicon 28.085

32

GeGermanium

72.630

50

SnTin

118.71

82

PbLead 207.2

7

NNitrogen 14.007

15

PPhosphorus

30.974

33

AsArsenic 74.922

51

SbAntimony 121.760

83

BiBismuth 208.980

8

OOxygen 15.999

16

SSulfur 32.06

34

SeSelenium

78.971

52

TeTellurium

127.6

84

PoPolonium

[209]

9

FFluorine 18.998

17

ClChlorine

35.45

35

BrBromine 79.904

53

IIodine

126.904

85

AtAstatine

[210]

10

NeNeon

20.180

2

HeHelium 4.003

18

ArArgon 39.948

36

KrKrypton 83.798

54

XeXenon

131.293

86

RnRadon [222]

56

BaBarium 137.327

87

FrFrancium

[223]

88

RaRadium

[226]

21

ScScandium

44.956

22

TiTitanium 47.867

39

YYttrium 88.906

40

ZrZirconium

91.224

57

LaLanthanum

138.905

72

HfHafnium 178.49

89

AcActinium

[227]

104

RfRutherfordium

[267]

23

VVanadium

50.942

24

CrChromium

51.996

41

NbNiobium 92.906

42

MoMolybdenum

95.95

73

TaTantalum 180.948

74

WTungsten

183.84

105

DbDubnium

[268]

106

SgSeaborgium

[269]

25

MnManganese

54.938

26

FeIron

55.845

43

TcTechnetium

[98]

44

RuRuthenium

101.07

75

ReRhenium 186.207

76

OsOsmium 190.23

107

BhBohrium

[270]

108

HsHassium

[269]

27

CoCobalt 58.933

28

NiNickel 58.693

45

RhRhodium 102.906

46

PdPalladium

106.42

77

IrIridium 192.217

78

PtPlatinum 195.084

109

MtMeitnerium

[278]

110

DsDarmstadtium

[281]

29

CuCopper 63.546

30

ZnZinc 65.38

47

AgSilver

107.868

48

CdCadmium 112.414

79

AuGold

196.967

80

HgMercury 200.592

111

RgRoentgenium

[280]

112

CnCopernicium

[285]

113

UutUnuntrium

[286]

114

FlFlerovium

[289]

115

UupUnunpentium

[289]

116

LvLivermortium

[293]

117

UusUnunseptium

[294]

118

UuoUnunoctium

[294]

How was the periodic table

formed?

In the

periodic table,

what is a

period? What

is a group?

What sub-atomic particle identifies an element?

In pairs, select three elements from the first two rows of the periodic table and create a model representation of their atomic

structure using materials provided. Display your model representation to the class. Can they determine which element it is?



What patterns can we find in the properties of elements in the periodic table?

METALLOIDS are solids with high melting points. Their crystals are hard to

break apart.Where would you find

metalloids in the periodic table?

The only gases found at room temperature are the

NON-METALS. They are made up of small

molecules which can move around freely.

Where are non-metals found in the periodic

table?

An element’s group gives clues about its structure. Consider gold,

silicon and chlorine; can you find them on the periodic table?

An element’s group gives clues to its structure. METALS are usually solids

at room temperature.The atoms typically form crystalline structures. Can

you think of any exceptions?Where would you look

for metals in the periodic table?

Click here to go to the digital resource Activity 1.4 and learn more about elements.

gold molecules

silicon molecules

chlorine molecules

gold crystals

silicon crystals

chlorine gas




Each atom of a particular element always has the same number of protons, but what about neutrons and electrons? Can their numbers differ between atoms of the same element?

An atom’s mass is equivalent to the number of protons and neutrons. Why, then, are the relative atomic masses (RAM) shown in the periodic table not whole numbers?

Write the symbols for these three isotopes.How many electrons will neutral atoms of each isotope have?

How many elements are shown in these diagrams?What are they? Are any of the atoms charged particles?

Draw symbols for each one.

WHAT IS AN ISOTOPE?All the atoms of the same element always contain the same number of protons, which gives the element its atomic number. However, the atoms can contain different numbers of neutrons, giving them different mass numbers.

Isotopes are atoms of the same element with different numbers of neutrons.

Lithium has 2 isotopes with mass numbers of 6 and 7.

6 7 Li Li3 3

A natural sample of lithium contains about 92.6% Li-7 and 7.4% Li-6, giving an average RAM of 6.97 on the periodic table.An element’s isotopes differ only by mass. They behave identically in chemical reactions.

Symbols to indicate different isotopes can be written like this carbon atom.

12 13 C C 6 6

mass number

element symbol

atomic number

HINT: use counters to help you here.

Click here to go to the digital resource Activity 1.5 and learn more about isotopes.

Use the "Build an atom" interactive to check your answers and construct your own isotopes.

Draw atomic models of these two isotopes.

ISOTOPES OF HYDROGEN

ATOMIC DIAGRAMS

neutron electronproton

H-1 Protium

A

D

B

E

C

F

H-2 Deuterium H-3 Tritium

+ + +

–

––

8p 7n

6p 8n

7p 9n

–

–

–

–

–

–

–

–

–

–

–

––

–

9p 7n

––

– –

–

–

–

–

–

–

–

–

8p 8n

––

–

–

––

––

– –

–

–

7p 7n

––

–

–––

–

––

15

ACTIVITY TYPE

ACTIVITY 1.5 ISOTOPES



http://phet.colorado.edu/en/simulation/build-an-atom

Activity 2.1 What is a chemical reaction?Activity 2.2 Conservation of massActivity 2.3 Ionic compoundsActivity 2.4 Writing chemical formulaeActivity 2.5 Sharing electronsActivity 2.6 It's falling apartActivity 2.7 Reactions in solutionActivity 2.8 Chemicals revised


PART

2PART 2: REACTIONS HAPPEN

What to use:

Each PAIR will require:

• dropper bottles of: dilute sulfuric acid ammonium hydroxide solution copper sulfate solution

• copper oxide powder • small pieces of clean magnesium

ribbon and granulated zinc • Bunsen burner and heating mat • 4 medium test tubes • test-tube holder • test-tube rack• matches • spatula• thermometer.

Each STUDENT will require:

• safety glasses and lab coat• Science by Doing Notebook.

What to do:

For each test, follow the instructions and record your observations in a table.

Test 1Add copper sulfate solution to one tube, to a depth of 10 mm. Add an equal amount of ammonium hydroxide solution. Shake gently to mix.

Test 2Place a piece of granulated zinc into a test tube and cover with 2 cm depth of copper sulfate solution.

Test 3Add dilute sulfuric acid to another test tube to a depth of 2 cm. Place a thermometer in the tube and record the temperature. Add a small piece of magnesium ribbon. Note the

temperature change as well as other observations.

Test 4Place 2 cm depth of sulfuric acid into a test tube. Use a spatula to add a pinch (about the size of a rice grain) of copper oxide. Heat gently until a change occurs.

Discussion:

• What was the most dramatic change you observed?

• Chemical reactions are associated with energy changes, which are detected by heat loss or gain. What evidence is there of energy changes in Tests 3 and 4?

• Can we reverse chemical changes?

CAN YOU RECOGNISE CHEMICAL CHANGES?

GOGGLESGLOVES

LAB COATSHOES

What makes

a good observation record?

Chemical reactions occur all around us. Some are fast and explosive, while others are slow and may take days or even months.

Can you think of examples? How can you tell they are chemical changes?

What makes a good observation record?

Test Reactants Observations Signs of a chemical change1 Copper sulfate

+ ammonium hydroxide

Starts blue then goes a cloudy pale blue when reagent two added.

Permanent colour change

Cloudy blue precipitate formed

17CHEMICAL REACTIONS PART 2 REACTIONS HAPPEN

ACTIVITY TYPE

ACTIVITY 2.1 WHAT IS A CHEMICAL REACTION?

REACTANT 1 + REACTANT 2 NEW SUBSTANCESenergy change

A chemical change produces new substances (elements or compounds). Look carefully for signs of a chemical change:

Can you see bubbles (gas) or a precipitate (solid) forming?

Has there been a permanent colour change?

Has there been an energy change? How would you measure this?

18

ACTIVITY 2.1 WHAT IS A CHEMICAL REACTION? CONTINUED

CHEMICAL REACTIONS PART 2 REACTIONS HAPPEN

LAW OF CONSERVATION OF MASS

In a chemical reaction, matter is neither created

nor destroyed.

The French scientist Antoine Lavoisier proposed the law of conservation of mass in 1789.

In this experiment we will test this law.

Scientists around the world

summarise their experimental

findings using a standard

format.

What should be included under

the following headings:

• Introduction/aim/hypothesis

• Method (including risk

assessment)

• Results • Discussion• Conclusion?

Where would you place your

experimental diagrams

and data tables?

What to use:


• 100 mL conical flask with stopper• small test tube • lead nitrate solution• potassium iodide solution• 10 mL measuring cylinder • electronic or beam balance.


• safety glasses• Science by Doing Notebook.

What to do:

Step 1Add 10 mL of lead nitrate solution to a test tube.

Step 2Add 10 mL of potassium iodide solution to the flask.

Step 3Carefully lower the tube into the flask, without spilling the contents.

Step 4Stopper the flask and weigh accurately. Record this mass.

Step 5Tip the flask upside down so the contents mix thoroughly, ensuring the stopper does not come loose.

Step 6Reweigh the flask. Record the mass.

Discussion:

1. How did the mass of the flask and contents before and after the reaction compare?

2. How could you use the results of other students in the class to support a more reliable experiment?

3. Did your data support the Law of Conservation of Mass?

4. Write up your experiment in a scientific report.

New substances are formed in a chemical reaction. What happens to the atoms in the

original substance?

HINT: Consider what you need to include under each heading and label your diagrams.

What do we mean when we refer to the reactants and products of a reaction?

GOGGLESGLOVES

LAB COATSHOES

THINK: If bubbles of gas were

given off in the reaction, would

mass still be conserved?

Do we lose or gain mass in a

chemical reaction? Use a sealed container

to find out what happens to the mass before and after

a chemical reaction.

stopper

conical flask

lead nitrate solution

potassium iodide solution

test tube

19

ACTIVITY TYPE

ACTIVITY 2.2 CONSERVATION OF MASS


What to do:In pairs, use the periodic table and your results from Activity 2.1 to complete these word equations in your Notebooks:

Indicate the state of matter for each reactant and product.HINT: sulfuric acid makes sulfates when it reacts with metals.

copper sulfate + ammonium hydroxide ?zinc + copper sulfate ?magnesium + sulfuric acid hydrogen + ?copper oxide + sulfuric acid water + ?If mass is neither lost or gained, are all the elements accounted for?

Click here to go to the digital resource Activity 2.2 and find out more about Antoine Lavoisier and conservation of mass.

hydrogen (g) + oxygen (g) water (l)

2 g + 16 g 18 g

A chemical reaction has occurred because the hydrogen and oxygen elements have combined to form the compound water. However,

we have the same amount and types of matter (elements) in the

reactants and the products, confirming the law of

conservation of matter.

This shows that mass is conserved in the reaction.

If we look at the number of atoms of hydrogen (H) and oxygen (O) involved in the reaction, we can see the

same number of atoms on both sides of the equation.

O

HH

HHH H

O

O

H HO

WATERChemical changes can be represented by equations. How can we show the numbers of atoms of each element in reactants and products?

The word equation for the reaction you have just carried out is:

lead nitrate (aq) + potassium iodide (aq) lead iodide (s) + potassium nitrate (aq)

The same particles are present on both sides of the equation.

When writing chemical equations, scientists use abbreviations to denote states of matter:solid (s) liquid (l) gas (g) dissolved in water/aqueous (aq) precipitate (ppt)

lead nitrate lead iodidepotassium iodide potassium nitrate+ +

ACTIVITY 2.2 CONSERVATION OF MASS CONTINUED



WHY DO ELEMENTS COMBINE? During a chemical reaction, atoms

of different elements may lose, gain or share electrons to become

more stable.

A compound’s chemical properties depend on the outermost

electrons, as these determine what kind of bonds are formed with

other atoms.

IONIC COMPOUNDS are formed when atoms lose or gain electrons to

form complete outer shells. Gaining or losing electrons results in positively or negatively charged IONS, hence the

term ionic compounds.

...I was cold and needed a

shirt.I was a bit

too hot wearing this massive

shirt...

Stable and settled: sometimes it makes more sense to hang out with others if it’s a win-win situation. Consider the sodium and chlorine atoms below. Why do they make good “friends”? What other elements of the periodic table would be keen to meet?

The outermost shell (energy level) is most stable with its maximum number of electrons: two electrons for the energy shell closest to the nucleus and eight for other shells.

Why do elements form compounds?

Which elements form ionic

compounds?

STABLE AND SETTLED?

COMPOUNDS FORM WHEN

ELEMENTS COMBINE IN

A CHEMICAL REACTION.

What to use:

• coloured disks, buttons or smarties.

What to do:

Step 1In pairs, place buttons to show the outer-shell electrons for the following atoms: sodium, magnesium, chlorine, oxygen.

HINT: refer to the periodic table for atomic number and shell configuration.

Step 2Place two elements together which are likely to form a stable ionic compound.

Discussion:

• What did you notice about your pairs?

• How do you use the periodic table to distinguish metals from non-metals?

• How would you form stable ionic compounds from other metal/non-metal combinations above?

Na 2, 8, 1

electron

Cl 2, 8, 7

17p 17n

11p 11n

––––

–––– –

––

–

–

–––– ––

––

–

–

–

–

–

––

ACTIVITY TYPE

21

ACTIVITY 2.3 IONIC COMPOUNDS


What to do:Draw the electron structure for magnesium ion. What charge would it have? Name an element ion that it would attract.

–

–

Sodium chloride crystal is formed from sodium ions and

chlorine ions arranged in a lattice structure

Non-metals gain electrons to achieve a full outer shell.

Chlorine is in Group 7 and so needs 1 more electron to complete its outer shell, forming a Cl– ion.

Elements in Group 6 need two electrons and form 2- ions. Elements in Group 5 gain three electrons to form 3- ions.

Cl- Cl-

Cl-

Cl- Cl-

Na+

Na+

Na+ Na+

Click here to go to the digital resource"Build an atom" interactive and construct the atoms and ions of the elements shown in the table.

How do the outer electrons determine what kinds of bonds form with other

atoms?

Metals lose their outer-shell electrons, leaving a new outer shell completely filled. The loss of electrons results in positive ions. The total charge on the ion depends on the number of electrons removed from the outer shell.

SODIUM is in Group 1, so loses one electron to leave a full outer shell and form a Na+ ion.

MAGNESIUM is in Group 2 and so loses two electrons to form a Mg2+ ion.

A Group 3 element such as aluminium will form ions with a 3+ charge.

–

–

–

HOW DO NEGATIVE IONS FORM?WHY DO POSITIVE IONS FORM?

–

–

sodium atom Na 2, 8, 1

chlorine atom Cl 2, 8, 7

sodium ion Na+ [2, 8]+

chlorine ion Cl– [2, 8, 8]–

-e11p 11n

11p 11n

+– –

– –

– –– –– –

– –

– –– –– –

– –

–

+e

–

17p 17n

17p 17n

– –– –

– –– –– –

– –

– –

–

– –– –– –

– –– –

– –

– –

– –

– –

– –

Elements which form positive ions

symbolElements which form negative ions

symbol

hydrogen H+ fluorine F–

lithium Li+ oxygen O2–

magnesium Mg2+ chlorine Cl–

aluminium Al3+ nitrogen N3–

ACTIVITY 2.3 IONIC COMPOUNDS CONTINUED


http://phet.colorado.edu/en/simulation/build-an-atom

RULES

There are millions of chemicals made up of one or more of about a hundred elements. How do scientists recognise them all?

Each chemical has its own unique chemical name and formula so that scientists know what elements are present and understand the properties of the substance.

1

HHydrogen

1.008 3

LiLithium 6.941

19

KPotassium

39.098

20

CaCalcium 40.078 15

PPhosphorus 30.974

16

SSulfur 32.066

53

IIodine

126.904

lead nitrate

lead iodide

potassium iodide

potassium nitrate

What to do:

Can you name the following ionic

compounds? What are they made of?

What electrons did they exchange?

HINT: refer to your periodic table

and complete in your Notebooks.

a) NaCl sodium + chlorine

b) MgBr2

c) KFd) Ag2O

e) ZnS

f) Ca3P2

g) Li3N

h) BaI2

i) SrCl2j) PbI2

Play the

to help interpret

formulae.

What to do:• Make pairs of cards with the

formula on one card and the corresponding name on the second card. Complete a memory card set using all the formulae on this page, along with any others you may know already.

• Shuffle and lay them face down on the table.

• Play the game with your partner.

Who got the most pairs?

PbI2

NaCl

sodium chloride

lead iodide

MEMORY CARD GAME

iron oxidecalciu

m carbonate

HOW DO WE NAME COMPOUNDS? First we will look at compounds formed by metals.Metals form ionic compounds with non-metal elements.Examples are iron oxide, tin sulfide, potassium iodide, calcium carbide.The rules for naming ionic compounds are:• the metallic element is named first (iron, tin, sodium,

calcium)• the name of the non-metallic element is last, but the

ending of its name is changed, so that it ends in – ide.

So oxygen becomes OXIDE, sulfur becomes SULFIDE, iodine becomes IODIDE, carbon becomes CARBIDE.What would nitrogen and bromine become?For example: what is the name of a compound with the formula CaCl2?Ca = calcium Cl = chlorine, so the compound is calcium chloride.Don’t worry about how many atoms of each element in the compound there are at this stage.Metals also form ionic compounds with ions made up of two or more elements to form compounds such as nitrates, sulfates, hydroxides and carbonates. We will consider the formulae for these in the next activity.

sodium chloride



What to use:

Your teacher will provide beakers of five test liquids, labeled A-F. Your task is to discover which contain dissolved ionic compounds.This activity will be set up as a class experiment, with each group setting up one station.

Each GROUP will require:

• transformer (set to 6 V)• electrodes with globe or LED• beaker of one of the liquids, A-F. • tapping key or switch• 2 electrical leads.



What to do:

Step 1Set up the equipment as shown in the diagram.

Step 2Check the circuit by briefly closing the switch and touching the electrodes together.

Step 3Close the switch briefly and note if the globe glows. Record your result in a table.

Step 4Repeat Step 3 for the five test solutions.

Discussion:

1. Which liquids do you think are solutions of ionic compounds? When you have decided, ask your teacher to identify liquids A-F and add the names to your table. You might know the formulae for some.

2. How were the solutions able to carry the electric current?

3. Why do solutions that contain molecules e.g. sugar solution, not conduct electricity?

4. Normal tap water will conduct electricity to a small extent (not enough to make the light glow) but distilled water does not. Why not?

WHY DO SOLUTIONS OF IONIC COMPOUNDS CONDUCT ELECTRICITY? Ionic compounds are held together in the solid state by the attraction of opposite charges. Unlike many other crystal forms, most ionic crystals are soluble in water. How does this happen?

Water molecules are polar (have a positive and negative end) and so can attract the charged particles in the ionic compound. This breaks the crystal apart and causes the salt to dissolve. The ions are then free to move through the solution and carry a current.

Click here to go to the digital resource Activity 2.3 and look at this simulation of salt dissolving in water.

Cl-

Cl-

Cl-

Cl-Na+ Na+

Na+

Na+

Na+Cl-

+H

+H+H

+H

+H +H

-O

-O -O Na+

+H +H-O

+H +H-O

+H

+H

-O

Na+

+H +H-O

+H +H-O

+H

+H

-O

+H

+H

-O

DISTINGUISHING IONIC SOLUTIONS.

GOGGLESGLOVES

LAB COATSHOES

solution of compound

electrodes

globe (or LED)

electrical circuit




The cross-over method can help to write formulae. Here are four easy steps:

Work out the symbols for the elements involved in the correct order from the

name. The example is aluminium oxide.Al O

Place the valency at the top of the element. Al3+ O2-

Cross over each valency number as subscripts. Al3+ O2-

Remove the valencies at the top to write the final formula.

Al2O3

Have you got it right? If the formula is correct, the total charge in the formula should be zero, as the positive and negative charges balance out.e.g. sodium chloride 1+ + 1- = 0

formula is NaCl magnesium chloride 2+ + (2 x 1-) = 0

formula is MgCl2

RULES

TO DETERMINE THE FORMULA OF AN IONIC COMPOUND, YOU MUST KNOW THE VALENCIES OF THE IONS INVOLVED. Here are some simple rules for calculating valency. Hint: you will need your periodic table.• The valency of a metal in Groups 1,2 and 3 is the same as the

group number; e.g. metals in Group 1 always have a valency of 1+.

• Metals in Group 4 often have a charge of 4+, but can have a charge of 2+. Assume the valency is 2+ unless you are told otherwise.

• Transition metals have a variety of charges but most have a valency of 2+.

NOTE: you will usually be given the valency of these metals.• If a metal has more than one valency, then the valency for that

compound is shown using Roman numerals. e.g. iron forms ions with 2+ and 3+ charges. Fe(II) is Fe2+ and Fe(III) is Fe3+.

• Non-metals in Groups 5-8 have valencies corresponding to the number of electrons needed for a complete outer shell of eight electrons. Those in Group 5 have valency 3-, Group 6 have 2- and Group 7 have 1-. Non-metals in Group 4 may form 4- ions.

Valency is the combining power of an atom or ion.

What to do:In a group of 2-4, select two of the above rules and explain them to the class. Don’t forget to use examples and refer to the periodic table to illustrate.

Some ions are made up of more than one element. These are called POLYATOMIC ions. You should become familiar with their names and valencies.

POLYATOMIC IONS

Add each of these polyatomic ions to your set of cards and play the

Click here to go to the digital resource Activity 2.4 and practise writing formulae.

Step 1

Step 2

Step 3

Step 4

MEMORY CARD GAME

2 3

phosphate

PO4

3-

polyatomic ionformula/valency (as used in compounds)

nitrate NO3-

sulfate SO42-

carbonate CO32-

phosphate PO43-

hydroxide OH-

ammonium NH4+

25

ACTIVITY TYPE

ACTIVITY 2.4 WRITING CHEMICAL FORMULAE



Molecules form when atoms combine to become more stable. They share electrons to achieve a full outer shell. Molecules are all around us. Can you name a few?

YOU HAVE JUST TAKEN

IN BILLIONS OF MOLECULES!

TAKE A DEEP BREATH!

What did you breathe

in?

What will your body

need?

Will you breathe it all out?

How many?

These are mainly nitrogen (about 80 per cent) and oxygen (about 20 per cent) with smaller amounts of water vapour, carbon dioxide and noble gases such as argon and neon. Depending on your location, there may also be pollutants. Can you think of some? N

HH

O

O

OC

26

ACTIVITY TYPE

ACTIVITY 2.5 SHARING ELECTRONS


NAMING COVALENT COMPOUNDS. Covalent compounds are formed when two non-metallic elements combine.Unlike ionic compounds, the name of the covalent compound must tell us the number of atoms of each element present.

The rules are:1. First name the element closest to the left

of the periodic table.2. Change the ending of the second

element to -ide as for ionic compounds.3. If more than one atom of an element is

present, use a prefix before the name, as shown in the table.

Note: The prefix mono is never used for the first element, but can be used for the second element. e.g. CO is carbon monoxide and CO2 is carbon dioxide.

RULESWhat to do:The atoms in a molecule may be of the same element, or different elements. Most are non-metals. What could be the reason?

Can you name the following compounds?

CO CO2 SO2 SO3 CCl4Which one is found naturally in the air and in the ground? Which one would you consider to be a toxic pollutant?Use the teacher worksheet to practise writing molecular formulae.

HH N N N

O

OS

O OO O

The NOBLE gases – Group 8Why are these gases: helium, neon, argon, krypton, xenon and radium less or non-reactive? Draw their electron structure to find out.

Some molecules consist of more than two atoms, and two or more elements like methane (CH4) and carbon dioxide (CO2).

HINT: look at the right side of the periodic table to remind you of element combinations which like to form covalent compounds.

"Covalent bonds" are formed when the atoms that make up a

molecule share their outer electrons. All then have a full outer

shell, with some electrons used by two atoms.

Sometimes it makes good sense to share.

WHO LIKES TO SHARE?

WHO DOESN'T NEED TO SHARE?

prefix number of atomsmono (see note) 1

di 2

tri 3

tetra 4

penta 5

hexa 6

27

ACTIVITY 2.5 SHARING ELECTRONS CONTINUED


–

–

–

–

–

––

–

–

–

–

–

Models of molecules help us understand their structure and shape.

What to use:


• molecular model kit.


• Worksheet• Science by Doing Notebook.

What to do:

Use the kit to construct molecules on your worksheet.

Step 1First draw a diagram of the molecule to show sharing of electrons (you only need to draw the outer shell).

Step 2Decide what type of bond is present by looking at the number of electrons shared.

Step 3Draw your model in 3-D.

Atoms need a full outer shell of electrons to be stable. If their outer shell is at the first energy level around the nucleus, only two electrons are required for stability. Eight are needed for all other shells. Instead of giving away outer electrons, some atoms prefer to become stable by sharing.

When a molecule of hydrogen (H2) forms, each atom has one atom in the first energy shell. Two atoms combine to form an full outer shell of two electrons. This forms a SINGLE COVALENT BOND.

A molecule of oxygen (O2) has atoms with six electrons in the outer shell. If they combine and share two electrons each, then both atoms have a full outer shell and a DOUBLE BOND forms.

A molecule of nitrogen (N2) has atoms with five electrons in the outer shell. If they share three each, then both atoms have access to eight electrons in the outer shell and a TRIPLE BOND is formed.

Take a good look at these molecules. What is being shared? Why?

HOW DO MOLECULES FORM?MODELLING MOLECULES

HH C

H

H

–

–

CH H

H

H

––

–

–

– –

–

–

– –H HSingle bond

H – H

– –

– –

O O

– –

– –

– –

– – Double bond

O = O

–

–

–

–

– –

– –

N N

– –

– –

Triple bond

N N

–

–

–

–

–

–

28

ACTIVITY 2.5 SHARING ELECTRONS CONTINUED


Elements are pure substances that cannot be broken down. One way to distinguish an element from a compound is to see if it will break down into simpler substances. This type of reaction in compounds is called a DECOMPOSITION REACTION.

Teacher demonstrationYour teacher will use a voltameter to decompose water. Watch carefully, then answer the questions.

Discussion:1. What substances are produced

when water decomposes?2. Where did the energy come from

to split the water molecule?3. What evidence did you have to

determine what the products of the decomposition reaction were?

4. How did the quantities of gas produced relate to the chemical formula for water, H2O?

5. Write a word equation for the chemical reaction that occurred. Include the states of the reactant and products as subscripts. You may like to also write an equation using chemical formulae.

6. Is it possible to reverse this reaction? Explain.

DECOMPOSITION OF WATER BY ELECTROLYSIS

Electrolysed acidic waterElectrolysed reduced water

ee

H

H

H

H O

O

O

O O

O

O

O

O

H

H

H

H

Oxygen gasis produced at

the positiveelectrode

(anode)

Hydrogen gasis produced atthe negative

electrode(cathode)

CAT

HO

DE

-

ANO

DE

+

ion

exch

ange

mem

bran

e

ELECTROLYSIS OF WATER

H HO H HO

29

ACTIVITY TYPE

ACTIVITY 2.6 IT'S FALLING APART


DECOMPOSITION OF COPPER CARBONATE Chemical reactions, such as decomposition

reactions, require energy.

This can come from heat, light or electricity.

test tube with copper carbonate

retort stand and clamp

bunsen burner

test tube of limewater

delivery tube

GOGGLESGLOVES

LAB COATSHOES

What is copper carbonate made of? Is it an ionic or covalent compound?

What to use:


• 2 large test tubes• stopper with delivery tube• copper carbonate powder• spatula• test-tube rack• limewater• Bunsen burner and mat • retort stand and clamp• lighter or matches.



What to do:

Step 1Use the spatula to place about 1 tsp of copper carbonate in a tube.

Step 2Insert the stopper and delivery tube.

Step 3Half fill a second tube with limewater.

Step 4Set up the equipment as shown in the diagram, ensuring the delivery tube’s end is below the limewater’s surface.

Step 5Light the burner and heat the tube gently, using a blue flame, until you observe changes to the copper carbonate and the limewater.

Step 6Turn off the burner and remove the delivery tube from the limewater to prevent liquid sucking back as the apparatus cools.

Discussion:

1. Describe the changes observed indicating a chemical reaction had occurred.

2. Can you identify the gas produced? Explain.

3. The solid remaining in the tube is copper(II)oxide. Write a word equation for the decomposition reaction that occurred.

NOTE: The only reactant is copper carbonate.

4. Write the formulae for the reactants and products in the reaction. Are they elements or compounds?

ACTIVITY 2.6 IT'S FALLING APART CONTINUED


PRECIPITATION REACTIONS

What to use:


• 5 test tubes in a rack or spotting tile

• dropper bottles of the following solutions:

• copper(II)sulfate• sodium hydroxide • cobalt(II)chloride• silver nitrate• sodium carbonate • barium nitrate.



What to do:

Step 1Draw a table in your Notebook with the following headings: reactants, ions present, precipitate (ü/û), name and formula of precipitate.

Step 2Place three drops of copper sulfate solution onto your spotting tile.

Step 3Add three drops of sodium hydroxide solution and look for a precipitate. Now complete the first three columns of your table.

Step 4Repeat steps 1-3 using the following combinations of solutions:• silver nitrate and sodium hydroxide• copper(II)sulfate and sodium

carbonate• cobalt(II)chloride and sodium

hydroxide• barium nitrate and copper(II)sulfate• barium nitrate and sodium

hydroxide

Step 5Rinse the spotting tile carefully under the tap.

Discussion:

1. Explain what happens when the solutions are mixed to form a precipitate.

2. Use the table of solubility on the next page to determine each precipitate and complete the final column of your table.

3. Write a word equation for each of the reactions that occurred. Use subscripts to indicate whether a solution (aq) or precipitate (ppt) has formed.

4. Write the formula for each ionic compound under its name.

5. Write the formulae for the reactants and products in the reaction. Are they elements or compounds?

GOGGLESGLOVES

LAB COATSHOES

IS THERE A PRECIPITATE?A coloured liquid that is clear does not contain a precipitate.Look for a swirl of white or colour in your mixture to indicate a precipitate has formed.

When solutions of ionic compounds are mixed they sometimes react to form an insoluble solid or PRECIPITATE.

31

ACTIVITY 2.7 REACTIONS IN SOLUTION

ACTIVITY TYPE


When ionic compounds dissolve, the positive and negative ions separate and are free to move around in the solution. e.g. sodium chloride splits up into Na+ and Cl– ions.

If a solution of another ionic compound is mixed with the sodium chloride solution, there will be two positive and two negative ions in the mixture. If there is a very strong attraction between any of the positive and negative ions, they join to form a solid precipitate.

Look at the example in which silver nitrate (AgNO3) is mixed with a sodium chloride solution and a precipitate of silver chloride is formed. The sodium and nitrate ions are not attracted, so remain free in the solution. This can be represented by the following equation.

NaCl (aq) + AgNO3 (aq) AgCl (s) + NaNO3 (aq)

Cl– (aq) + Ag+ (aq) AgCl (s)

NO Na Cl Solid AgCl+Ag+ --3NO Na Cl Solid AgCl+Ag+ --3 NO Na Cl Solid AgCl+Ag+ --

3

Cl-

Cl-

Cl- Cl-

Cl-

Cl-

Ag+

Ag+

Ag+

Ag+

Ag+

Ag+

Ag+

Ag+Ag+

Ag+

Cl-

Cl-

Cl-

solution suspension supernate

precipitate

+

ACTIVITY 2.7 REACTIONS IN SOLUTION CONTINUED


You can predict what a precipitate might be with the table of solubility.

Use the solubility rules table to answer these questions.

1. Which of the following ionic compounds are soluble in water? a) aluminium chloride, AlCl3 b) iron(II)hydroxide, Fe(OH)2 c) copper(II)nitrate, Cu(NO3)2 d) barium carbonate BaCO3

e) magnesium nitrate, Mg(NO3)22. For the following mixtures, write the formulae for the ions present.

Write the formula for any substances that will form precipitates. a) copper(II)sulfate and lead(II)nitrate b) potassium chloride and sodium hydroxide c) potassium hydroxide and silver nitrate d) sodium nitrate and copper sulfate e) barium chloride and sodium sulfate.

3. The ions that remain in solution are often called spectator ions. Why?

4. You are given three containers A, B and C each containing a clear, colourless liquid. The substances are sodium carbonate, sodium chloride and water. How would you identify them? No tasting!

MAKING PREDICTIONS

Click here to go to the digital resource Activity 2.7 and find out more about precipitation reactions.

negative ion soluble positive ions insoluble positive ions (form precipitate)

nitrate All soluble

chloride Na+, K+, Mg2+, Ca2+, Ba2+, Al3+, Cu2+, Co2+ Ag+

sulfate Na+, K+, Mg2+, Cu2+, Co2+ Pb2+, Al3+, Ag+, Ba2+

hydroxide Na+, K+, Mg2+ Cu2+, Al3+, Ca2+, Ba2+, Co2+, Ag+

carbonate Na+, K+ Mg2+, Ca2+, Ba2+, Pb2+, Ag+, Al3+, Cu2+, Co2+

ACTIVITY 2.7 REACTIONS IN SOLUTION CONTINUED



Am I a covalent or ionic

compound?

Am I on the left side of the periodic table?

YES! NO!

Am I an ionic

compound?

Am I a polyatomic

ion?

Do I contain oxygen?

A solid?

Pretty sure magnesium is an alkaline

earth metal...Um... what's the difference between covalent and ionic

again...

HINT: Before you start, consider the questions

you could ask and revise your CHEMISTRY MEMORY

CARD set.

MEMORY CARD GAME

PLAY

This time your teacher will give

you an element, compound or

ion to guess. See how you go!

WHAT IS THE MATTER?AGAIN

LEAD IODIDE

34

ACTIVITY TYPE

ACTIVITY 2.8 CHEMICALS REVISED


35

PART

3PART 3: ENERGY FROM THE NUCLEUSActivity 3.1 What is radioactivity?Activity 3.2 Researching radioactivityActivity 3.3 Detecting radioactivityActivity 3.4 How long does it last?Activity 3.5 Nuclear energyActivity 3.6 The future

CHEMICAL REACTIONS PART 3

Millisieverts (mSv)

Short-term

Annual

Acute

Medical X-Ray (Chest)(Also equivalent to 3,300 TSA Full Body Airport Scans)

Natural Radiation All People ReceiveAverage year

Natural Radiation in Special Locations

Average Exposure for a Uranium Miner

Airline Crew (New York to Tokyo-Polar Route)

3 Mile Island Accident

CT Scan (Brain)

CT Scan (Pelvis)

IS RADIOACTIVITY NATURAL?

Many radioisotopes occur naturally. They originated when the solar system

formed and by the interaction of cosmic rays with molecules in the atmosphere.

What to use:


• butcher paper • marking pen.

What to do:

Step 1In groups of three to four students, brainstorm what you know about radioactivity.Think about:What causes radioactivity?What can we use it for?Are there problems associated with its use?

Step 2On the paper list 10 things your group knows about radioactivity.

Step 3Display your list in the classroom and see what others have written.

Discussion:

• Are there common points on the lists?

• Is there anything you are unsure of?• In your Notebooks, write two

questions which your group can't answer for later. Keep your lists displayed and ready to add 5 bits of new information each lesson.

Click here to go to the digital resource Activity 3.1 and find out more about our exposure to natural radiation.

WHAT DO YOU ALREADY KNOW ABOUT RADIOACTIVITY?

RADIATION is energy from waves, such as radio waves, or fast-moving particles, such as light from the sun. It is all around us and all living things rely on some form of radiation to exist.

What is the difference between a chemical reaction and a nuclear

reaction?

ACTIVITY TYPE

36

ACTIVITY 3.1 WHAT IS RADIOACTIVITY?

CHEMICAL REACTIONS PART 3 ENERGY FROM THE NUCLEUS


Radioactivity was discovered accidentally by the French scientist Henri Becquerel. He stored a rock containing uranium in a drawer next to a photographic plate, covered in black paper. When the plate was developed, it showed an image of the rock. He won the Nobel Prize for Physics in 1903, together with Marie and Pierre Curie, for his work.

The Geiger–Müller counter, also called a Geiger counter, was invented in 1928. It measures radioactivity by detecting the ionisation produced in the decay of an atom, including the amount of alpha and beta particles and gamma rays. Although more sophisticated instruments are now available, the Geiger counter is still used extensively as it is portable.

Becquerel demonstrated that a metal cross blocked the radiation and left an unexposed image on the photographic plate.

Can you see the shape of the cross on the image?

What do you think caused it?

Henri Becquerel

Why do scientists

have two different ways of measuring

radiation?

HOW DO WE DETECT RADIOACTIVITY?

Click here to go to the digital resource Activity 3.2 and find out more about radioactivity.

Radioactive decay is

measured in "Becquerels" (Bq).

This is the number of atoms that decay per second.

A "Sievert" (Sv) is the

unit used for measuring the dose of radioactivity absorbed by the

body.

How many millisieverts

(mSv) are there in a sievert?

What is a microsievert (μSv)?

37

ACTIVITY TYPE

ACTIVITY 3.2 RESEARCHING RADIOACTIVITY



THE ISOTOPES OF CARBON

WHAT MAKES AN ATOM RADIOACTIVE?

C-12 and C-13 are stable but C-14 is unstable and radioactive.

If the nucleus of an atom is unstable, it is radioactive. This is usually because the isotope has more or less protons than neutrons. These unstable isotopes are called RADIOISOTOPES.

Energy

Particle

radiation

radioactiveatom

What to use:Each PAIR will require:

• access to computer simulation of α, β and γ radiation• Science by Doing Notebook.

What to do:Your task is to design and conduct an experiment to compare either:1. the range of α, β and γ radiation in air2. the penetration of α, β and γ radiation.

Step 1In your Notebook, plan a fair test for your investigation.NOTE: don’t forget to consider background radiation.

Step 2Draw up a table to record your results. How will you make the results reliable? Step 3Carry out your experiment and record the results. Step 4Write a practical report on your findings, under the correct headings, including:• an appropriate graph of your

results• a comparison of the properties

of the three forms of radiation and their implications for use and relative safety of radioisotopes.

INVESTIGATING RADIOACTIVITY

Click here to go to the digital resource Activity 3.3 and use a computer simulation of radiation.

When carbon-14 decays, nitrogen-14 is formed and a beta particle is emitted.

How is an atom of C-14 different to that of N-14?

Can you draw the symbols of each to find the number of protons and neutrons they contain?

Carbon-14

Nitrogen -14

Beta particle(electron)

6p 6n

6p 7n

6p 8n

– – –

– – –

– – –

– – –

– – –

– – –

carbon-12 (6 protons + 6 neutrons)



38

ACTIVITY TYPE

ACTIVITY 3.3 DETECTING RADIOACTIVITY



Click here to go to the digital resource Activity 3.3 and find out more about your exposure to radiation.

In your Notebook draw a table to summarise what you know about the properties of alpha, beta and gamma radiation.

Alpha, beta and gamma radiation can be separated using a magnetic field.

Alpha and beta particles have opposite charges, so will be deflected.

WHAT IS BACKGROUND

Paper Aluminium Lead

Alpha

Beta

GammaBeta ( ) particles

consist of an electron, so

carry a negative charge. They can travel a few metres through air.

Alpha ( ) particles are made up of two protons and two

neutrons, so they have a positive charge. They

can travel in air for only a few centimetres.

Gamma ( ) rays are not particles, but high-energy rays with no charge. They are emitted from nuclei with excess

energy and can travel several kilometres through air.

Gamma Gamma rays are not deflected as they have no charge

Beta -Alpha +

ACTIVITY 3.3 DETECTING RADIOACTIVITY CONTINUED

39CHEMICAL REACTIONS PART 3 ENERGY FROM THE NUCLEUS


Not all radioisotopes decay at the same rate. Each has its own characteristic HALF-LIFE, which can be as short as a fraction of a second or as long as millions of years. What is best, a short or long half-life?

RADIOACTIVE DECAYYou are about to simulate radioactive decay.We cannot know when a particular atom will decay, but we know the probability for a particular radioisotope if we have many atoms and know its half-life.

What to use:


• 100 plastic counters with a dot on one side

• bag to hold counters• large tray.

What to do:

Step 1Mix the counters in the bag, then carefully tip them on the tray.

Step 2Remove counters with an upward-facing dot.

Step 3Count the remaining counters.

Step 4Record your results in a table, as shown, in your Notebook.

Step 5Repeat steps 1 and 2 four more times.

Discussion:

1. What length of time does one trial represent?

2. What do the counters without dots represent?

3. Draw a line graph of your results and a line of best fit through your points (this should be a curve).

4. Does this radioisotope have a half-life of exactly a year? Calculate the average half-life.

5. Describe its pattern of decay.6. Iodine-131 has a half-life of eight

days. Calculate the amount left from a 20 g sample in: a) eight days b) 16 days c) 32 days

7. Why are large atoms more likely to be radioactive than smaller atoms?

Each radioisotope has its own characteristic half-life, which can vary from a fraction of a second to millions of years.

What would be problematic or useful about polonium-215 and uranium-238?

The HALF-LIFE of an isotope is the time it takes for one half of its atoms to decay.

Trial 0 1 2 3 4 5Counters without dots

100

Radioisotope half-lifepolonium-215 0.0018 seconds

bismuth-212 60.5 seconds

sodium-24 15 hours

iodine-131 8.07 days

cobalt-60 5.26 years

radium-226 1600 years

carbon-14 5730 years

uranium-238 4.5 billion years

40

ACTIVITY 3.4 HOW LONG DOES IT LAST?

ACTIVITY TYPE


It is important to know the half-life when determining the suitability of a radioisotope for a purpose. If the isotope is to be injected into the body for medical diagnosis, then it should have a very short half-life (no more than a few days) to minimise exposure to radiation. Isotopes with a very long half-life of thousands of years are useful in dating ancient artefacts.

Carbon-14 has a half-life of about 5,730 years. Scientists can use this long half-life to determine the age of organic objects less than 40,000 years old. By determining how much of the carbon-14 has decayed, they can estimate the age of a substance. Samples from the past 70,000 years made of wood, charcoal, peat, bone, antler, or one of many other carbonates, may be dated using this technique.

Isotopes with longer half-lives, such as uranium-238, can be used to date even older objects.

Artefacts such as the remains of early hominids and the Dead Sea Scrolls have been dated using carbon-14.

How is half-life information used in radioisotope dating?

How is half-life information used in radioisotope dating?

Carbon-14

remaining (%)

Number of half-lives

(1half-life=5730 years)

100

50

25

12.5

00 1 2 3 4

10g

5g

2.50g

1.25g

10g

5g

1.25g

Decay of Carbon-14

2.50g

CARBON DATING

Click here to go to the digital resource Activity 3.4 and find out about the use of radioisotopes in dating.

THINK!If a sample of carbon-14 decays at the rate of 400

particles per second, what will the rate be in 5,730 years time?

How long would it take to reach a rate of 50 particles

per second?

ACTIVITY 3.4 HOW LONG DOES IT LAST? CONTINUED

41CHEMICAL REACTIONS PART 3 ENERGY FROM THE NUCLEUS


H – H

What to do:

Use the teacher worksheet to

compare fusion with fission.

FISSION OR FUSION? It is easy to forget that nuclear reactions are essential for life and that controlled nuclear radiation can have many benefits. What are they? What are the dangers?

Nuclear fusion occurs when two nuclei combine, releasing a huge amount of energy. In the sun, two isotopes of hydrogen, deuterium and tritium, combine to form helium, releasing a neutron in the process.We rely on nuclear energy, generated inside the sun by fusion, to provide sunlight for plants to photosynthesise and so provide energy for all living organisms to survive. An advantage of this process is that no radioactive waste is produced and the hydrogen isotopes needed can be obtained from water. However, we are unable to control nuclear fusion and harness its energy safely. Temperatures of millions of degrees are needed to keep the fusion process going.

NUCLEAR FUSION Nuclear fission is the splitting of large atoms into smaller atoms, by bombarding them with a particle such as a neutron. An enormous amount of energy is released as heat and gamma radiation. At the same time, neutrons are released which can cause more fission reactions. A major problem is radioactive waste is created and must be disposed of safely.In 1945 the first atomic (uranium) bomb was released in the New Mexico desert. The explosion was so powerful; it lit up the sky for hundreds of miles, the noise was deafening and a huge crater was created. The Japanese cities of Hiroshima and Nagasaki were destroyed in this manner, which marked the end to the second world war in the Pacific.We have since learned how to control nuclear fission reactions to harness the energy for many productive purposes, such as electric power stations, nuclear submarines and ships.

NUCLEAR FISSION

neutron

tritium H 3 helium He 4

deuterium H 2

fusion

neutron

neutron

neutron

neutronuranium

barium

krypton

fission

Click here to go to the digital resource Activity 3.5 and investigate the nuclear energy and the uses of radioisotopes.

ACTIVITY TYPE

42

ACTIVITY 3.5 NUCLEAR ENERGY



Which is the biggest

killer, nuclear power or

coal?

Like most new and complex technologies, there is much controversy and misconception about nuclear power. From a health perspective, nuclear power is far safer than coal, especially with concerns about global climate change.

The World Health Organization estimates more than 125,000 people die each year prematurely from inhaling the combustion products of fossil fuels, a large percentage of which comes from burning coal.

While a coal-burning power station will receive a trainload of coal every day, a nuclear fission power station might receive a truckload of nuclear fuel once a year. A coal-burning station consumes about 300,000 times as much fuel to generate the same amount of power as a nuclear station.

This means the amount of waste from coal-fired power stations is much greater and there are concerns about environmental contamination with toxic metals and radioactivity.

Many people are killed in coal mining accidents all over the world, whereas accidents at nuclear power stations are infrequent, even though some have had drastic effects on people and the environment.

The US armed forces have successfully operated about 150 nuclear power vessels, one for more than 40 years. The US has more than 120 functional nuclear reactors. France and several other European nations generate almost all power from nuclear reactors. France is the only nation which today produces less carbon dioxide emissions than it did 30 years ago.

The track record of nuclear power is so good, some analysts consider it the safest form of energy yet developed.

NUCLEAR POWER OR COAL POWER?

Australia has the world’s biggest supply of uranium, yet we don’t

have any nuclear power stations. What do we do with it?

Should we consider nuclear power in the future or would it be better to utilise solar, geothermal

or wind energy?

What about accidents in

reactors?

What about radioactive wastes?

Can radioactive materials leak out?

Will the environment become contaminated?

There is great concern that the world is using its non-renewable energy resources too quickly. In Australia a large percentage of electricity is generated from coal-fired power stations. Should we invest in nuclear power as an alternative to fossil fuels?

Can people use

nuclear reactors

for harmful purposes?

43

ACTIVITY TYPE

ACTIVITY 3.6 THE FUTURE


CLASS DEBATE RULES:1. Your teacher will post the debate topic on the board

and assign you to either the affirmative or negative team.

2. Your team will have one lesson to prepare your arguments. Make sure everyone has a good opening and closing point, and scientific facts to support their arguments.

3. At the beginning of the debate each team member will be listed on the board. As you are invited to speak (not in the same order as on the list), your name will be crossed off.

4. You will speak for 30-90 seconds – either rebutting earlier speakers or defending your team’s position by emphasising previous comments and additional arguments with examples to illustrate.

5. Marks will be deducted for talking. You can pass paper notes to team members who are yet to speak throughout the debate.

6. Each speaker will be scored out of three to reflect the quality and content of their effort. Students relying on scientific facts and sound arguments will score higher. The teacher records individual marks and the team with the highest cumulative score wins.

Click here to go to the digital resource Activity 3.6 and continue your discussion on future energy options.

44

ACTIVITY 3.6 THE FUTURE CONTINUED



PART

4PART 4: ENERGY AND CHANGEActivity 4.1 What is energy?Activity 4.2 Hot and coldActivity 4.3 CombustionActivity 4.4 Reactions in natureActivity 4.5 Industrial chemistry


Click here to go to the digital resource Activity 4.1 and find out more about energy changes in chemical reactions.

A change in temperature, getting hotter or colder, is a good indicator of a chemical reaction taking place – even if you can’t see anything happening. Can you think of any examples?

ENERGY MAKES THINGS HAPPEN!Use the images on this page to help you think of chemical reactions that release energy.

What forms of energy are

given off?

Your teacher will demonstrate some

reactions which show energy

changes.

GOGGLESGLOVES

LAB COATSHOES

Chemical reactions that produce heat are called EXOTHERMIC REACTIONS.

Chemical reactions that take in energy and make things colder are called ENDOTHERMIC REACTIONS.

46

ACTIVITY TYPE

ACTIVITY 4.1 WHAT IS ENERGY?

CHEMICAL REACTIONS PART 4 ENERGY AND CHANGE


HEAT PACKSHeat packs are also used for sports injuries and medicinal purposes. They rely on an exothermic chemical reaction.When would they be useful?How do they work? Are different chemicals involved? Research one commercial heat therapy pack which relies on a chemical reaction.

ICE PACKSYou have probably used an ice pack to prevent swelling, e.g., for a sprained ankle.

What to use:


• instant ice pack• thermometer.

What to do:

Carefully cut an ice pack open and mix the contents in a beaker using a thermometer. What is happening to the temperature? An ice pack contains chemicals which, when mixed, carry out an endothermic reaction to make the pack cold.Some packs use ammonium chloride and water in separate compartments. The ammonium chloride is released into the water when you activate the pack.

Ouch! Can’t find ice? Activate a first aid instant ice pack to quickly cool the site of an injury. How do they work? What is in them?

Short-term heat and cold packs are used for other purposes, such as exporting plants or reptiles in cargo planes. Can you think of other potential uses?

GOGGLESGLOVES

LAB COATSHOES

Contents: Magnesium

sulfate and water

47

ACTIVITY TYPE

ACTIVITY 4.2 HOT AND COLD


What to use:


• calcium chloride solid• sodium acetate solid• ammonium chloride • sodium thiosulfate solid• clean magnesium ribbon • manganese dioxide powder • dropper bottle of hydrochloric

acid • dropper bottle of hydrogen

peroxide • 5 large test tubes • test-tube rack• spatula or teaspoon • thermometer or temperature

probe.



What to do:

Step 1Construct a table in your Notebook similar to the one shown, making sure you can record the temperature before and after each reaction, along with your observations.

Reaction 1Add 4 cm depth of water to a test tube. Measure the temperature of

the water. Carefully add a teaspoon of calcium chloride. Stir gently with the thermometer to dissolve. Record the highest temperature reached.

Reaction 2Add 4 cm depth of water to a test tube. Add a teaspoon of ammonium chloride.

Reaction 3Place 4 cm depth of hydrochloric acid into a test tube. Add two 1 cm pieces of magnesium ribbon.

Reaction 4Place 4 cm water into a test tube. Add 1 tsp of sodium thiosulfate.

Reaction 5Place 4 cm hydrogen peroxide solution into a test tube. Add ½ tsp of manganese dioxide.

Reaction 6Add 4 cm depth of water to a test tube. Add a teaspoon of sodium acetate.

Discussion:

1. Complete your table by adding the temperature rise or fall and decide if the reaction is exothermic or endothermic.

2. What other signs of a chemical reaction did you observe? Were all reactions obvious?

3. Explain in terms of energy changes why some chemical reactions are endothermic and others exothermic?

TEMPERATURE CHANGES IN CHEMICAL REACTIONS

EXOTHERMIC OR ENDOTHERMIC?When you observe chemical reactions,

look for a temperature change.

GOGGLESGLOVES

LAB COATSHOES

Exothermic Endothermic

Heat Heat

HOTTER THANSURROUNDINGS

Heat Heat Heat Heat

COOLER THANSURROUNDINGS

ReactantsInitial temperature (°C)

Final temperature (°C)

Change in temperature (+/-°C)

Exothermic or endothermic

Other signs of a chemical reaction

Water + calcium chloride

Endothermic reaction

Exothermic reaction

Reaction pathway

Heat is absorbed

Reactants

Reaction pathway

Products

Reactants

Po

ten

tial e

ner

gy

(kJ)

Po

ten

tial e

ner

gy

(kJ)

Heat is released

Products

ACTIVITY 4.2 HOT AND COLD CONTINUED

48CHEMICAL REACTIONS PART 4 ENERGY AND CHANGE

What to do:Carefully prepare and light: a match, a Bunsen burner, a liquid-fuel camping stove (e.g., Trangia). How are they different? For each, discuss the following questions in your group: What do you observe? What is released? How do you know a chemical reaction is taking place? How does the reaction start? How do you stop it? Does combustion take place?Try writing a combustion word equation for each.

WHAT IS THE IGNITION TEMPERATURE OF A FUEL?Substances will only start to burn (ignite) if the temperature is high enough to give reacting particles the energy they need to break their chemical bonds. Vapours and gaseous fuels will ignite more easily than liquid or solid fuels. Ignition sources include friction, matches, lighters and electricity.

How do bushfires start? Click here to go to the digital resource Activity 4.3 and explore bushfires and the control of combustion.

When was the last time you

lit a match? Did you start

a chemical reaction? Did

combustion take place?

Why do we need to ignite

fuels to release the energy

stored in them?

Is combustion an endothermic or exothermic

reaction?

WHAT IS COMBUSTION?Combustion is a chemical reaction in which a fuel reacts with oxygen to release energy in the form of heat and light.

fuel + oxygen combustion products + energy

49

ACTIVITY TYPE

ACTIVITY 4.3 COMBUSTION



What to use:


• Bunsen burner and heating mat • metal tongs• candle on stand• clean magnesium ribbon• hydrochloric acid• matches• wooden splint • 2 medium test tubes• test-tube rack.



What to do:

Record your observations in your Notebook after each step.

TEST 1Step 1Close the Bunsen burner air hole and ignite the flame with a match. • Describe the flame. What evidence

is there that energy is released in the combustion reaction?

Step 2Gradually open the air hole. • Describe the differences in the

flame.

Step 3Hold a 2 cm piece of magnesium in the hottest part of the flame(see diagram). Take care not to look directly at the flame. • What did you observe during and

after combustion?

TEST 2

Step 1Add 4 cm depth of hydrochloric acid to a test tube. Have a second inverted test-tube ready to collect the gas produced after adding two small (1 cm) pieces of magnesium ribbon.

Step 2When the reaction has stopped, light a wooden splint and quickly place it at the top of the second test tube with the collected gas (now in the test-tube rack). • What did you observe when you

ignited the gas?• Do you

know the name of this gas?

Discussion:

1. Use the formulae to write a word equation for the combustion of methane (natural gas). What else is produced that indicates a chemical reaction has taken place?

2. What are you regulating when you open and close the air hole? How does this impact on the amount of heat and light? Which flame is coolest? Why?

3. Incomplete combustion results in carbon monoxide and carbon (soot), which gives the yellow colour to the flame. When complete combustion of methane occurs we cannot see the products. Why? Write a possible word equation for incomplete combustion.

4. Write a word equation for the reaction of magnesium in Step 3. Include the formulae for each substance underneath its name. How do you know this was a combustion reaction?

5. Write a word equation for the combustion reaction that occurred in Test 2. What is the chemical formula for the product?

6. Write a general word equation to describe combustion.

OBSERVING COMBUSTION

GOGGLESGLOVES

LAB COATSHOES

unburnt gas

hottest part of the flamecomplete combustion

combustion of methane formulae

H

O

O

H

O O

H

O O

H

O O

H

H

H

H

O O

O

O

C

O O

O OC

O

O

C

OC

fuel

+ +

CH4 + 2O2 CO2 + 2H2O

ACTIVITY 4.3 COMBUSTION CONTINUED


Photosynthesis uses solar energy to convert carbon dioxide into glucose, which is stored as carbohydrates.

carbon dioxide + water + sunlight energy glucose + oxygen

6CO2 (g) + 6H2O (g) C6H12O6 (aq) + 6O2 (g)

All living things release energy from carbohydrates during respiration.

glucose + oxygen carbon dioxide + water + energy

C6H12O6 (aq) + 6O2 (g) 6CO2 (g) + H2O (g)

Lightning causes nitrogen in the air to form nitrates.

nitrogen + oxygen nitrogen dioxide

N2 (g) + 2O2 (g) NO2 (g)

Carbon dioxide dissolves in water to form carbonic acid.

carbon dioxide + water carbonic acid

CO2 (g) + 6H2O (l) H2CO3 (aq)

What natural chemical reactions are suggested in

these pictures?

Reactions in nature are all around us. Could we stop or reverse them if we tried?

51

ACTIVITY TYPE

ACTIVITY 4.4 REACTIONS IN NATURE


CONCEPT MAPAll living things need energy to function and grow and this happens through chemical reactions. These reactions also shape the environment around us and produce new chemicals.

In a group, create a Concept Map to illustrate reactions in nature. Don’t forget to include reactions in living things, as well as reactions in the atmosphere and lithosphere. Use a key to highlight reactions which are:• beneficial and not-so

beneficial• short and longer term.

size/surfaceof particles

happen at

Chemical Reactions bubbles

form

colour change

temperaturechange

New substances form,old ones disappear.

reactionsinvolving light

combustionreactions

many types

Synthesis

there are

presence of catalyst

temperature

Different rates of speeds depending on

concentration

precipitationreactions

Solid products

e.g.making cheese

neutralisationreactions

decomposition

Reaction between a fuel and oxygen to release energy.

Reaction between anacid and a base.

hydrogen (g) + oxygen (g) water (I)

e.g.

e.g.

acetic acid (ag) (vinegar) + sodium bicarbonate (s) sodium acetate (ag) + water (I) + carbon dioxide (g)

ACTIVITY 4.4 REACTIONS IN NATURE CONTINUED


Click here to go to the digital resource Activity 4.4 and learn more about energy changes in the environment.

Organisms such as yeast can release energy without using oxygen by the process of "fermentation".

glucose carbon dioxide + water + energy

C6H12O6 (aq) 2CO2 (g) + 2C2H5OH (g)

In this investigation you will design an experiment to find out more about fermentation.

What to use:


• 4 or 5 small soft drink bottles• sachets of dry yeast (1 g per bottle)• teaspoon• 4 or 5 round balloons • 250 mL each of a variety of fruit

juices.



What to do:

Your task is to design and carry out a fair test to compare the rates of fermentation in different fruit juices.

Step 1Decide on an hypothesis and aim for your experiment.

Step 2Plan your experiment, making sure it:• answers the aim

• is carried out in controlled conditions

• is reliable (don’t forget replication).

Step 3Carry out your experiment, Notebooking your results as you go.

Step 4Write a full report on your experiment under the correct headings.

Discussion:

In your discussion, make sure that you:• include a graph and inferences

from the data you have collected• explain any differences in

fermentation rate• discuss whether your hypothesis

was correct• suggest improvements to your

experimental design.Can you suggest a more reliable way of confirming your findings?

WRITE A...

GOGGLESGLOVES

LAB COATSHOES

ACTIVITY 4.4 REACTIONS IN NATURE CONTINUED



Could we live without chemical products? Where do they come from? What are the implications when

industry and chemistry combine?

Chemical industries produce an amazing range of products, from eucalyptus oils to complex petroleum and pharmaceuticals. In a group, list as many products you can think of which are found in your bathroom, kitchen, garage or shed. Share your findings with the class.

54

ACTIVITY TYPE

ACTIVITY 4.5 INDUSTRIAL CHEMISTRY


Reaction occurs at 450ºCand at 200 atmospheres of pressure.

Liquid ammoniacollected when condensed.

Nitrogenfrom the air.

Hydrogen from naturalgas (methane).

Unused hydrogen andnitrogen do not condenseand are recycled. Waster gases from

combustion in heatingunit returned to air.

Refrigerationunit to cool gases.

CO2 OH2

NH3

HOW DO WE USE AMMONIA?Ammonia is used to make fertilisers, nylon, rayon, nitric acid, cleaning products and detergents.

Why does ammonia condense when cooled under pressure, but hydrogen and nitrogen do not?

Makingfertilisers

Making other chemicals

and wood pulp

Makingnylon

Makingnitric acid

% of total ammonia

100

90

80

70

60

50

40

30

20

10

0

Uses of ammonia

Globally, 40 million tonnes of ammonia are manufactured each year. How is it made?

Click here to go to the digital resource Activity 4.5 and learn more about industrial chemistry and the Haber process.

nitrogen + hydrogen ammonia

N2 (g) + 3H2

(g) 2NH3 (g)WHAT IS AMMONIA (NH3)?

Look at the labels on the cleaning liquids in your laundry cupboard. Which contain ammonia? Gently smell the contents of one.

WARNING: DON’T BREATHE IN DEEPLY!!

This smell is characteristic of ammonia, a colourless poison gas which can cause wheezing and breathlessness.

THE HABER PROCESSIn 1912 German chemist Fritz Haber developed a process to make ammonia from the readily available elements, hydrogen and nitrogen. This had a significant effect on world history, providing both fertilizers and explosives.

Use the diagram and digital resources to write a descriptive paragraph in your Notebook on the Haber process. Don't forget to name the reagents and waste products.

55

ACTIVITY 4.5 INDUSTRIAL CHEMISTRY CONTINUED



PART

5PART 5: ACIDS AND BASESActivity 5.1 Acid or base?Activity 5.2 IndicatorsActivity 5.3 The pH scaleActivity 5.4 NeutralisationActivity 5.5 Acids and metalsActivity 5.6 Acids and carbonatesActivity 5.7 Acids and bases everywhereActivity 5.8 Are you a chemist?


You probably know orange juice contains vitamin C (ascorbic acid), but did you know you were drinking an acid? Orange juice also contains citric acid, which gives its sharp taste. Are all acids dangerous?

WHAT IS LITMUS?Litmus is a natural dye extracted from lichen. Indicator papers are first soaked in litmus solution, then dried.

If neither red nor blue paper changes colour, the substance is neutral (neither an acid nor a base).

IF BLUE LITMUS PAPER TURNS RED, THE SUBSTANCE TESTED IS AN ACID.

IF RED LITMUS PAPER TURNS BLUE, THE SUBSTANCE TESTED IS A BASE.

Is this solution an acid or base?

Did you have a glass of orange juice this morning? What did you use to clean your teeth and wash your face? Which one is acidic?

ACTIVITY TYPE

ACTIVITY 5.1 ACID OR BASE?

CHEMICAL REACTIONS PART 5 ACIDS AND BASES 57

What to use:

The CLASS will require:

• beakers of labelled solutions stationed around the room.


• 10 pieces each of red and blue litmus papers.



What to do:

Step 1Construct a table in your Notebook with five headings: substance, formula, colour of red paper, colour of blue paper, acid/ base/neutral.

Step 2Dip red and blue litmus papers into each solution, taking care not to get the solution on your fingers, as this will spoil the paper. Dispose of used paper in the container provided.

Discussion:

1. Group the solutions as acid, base or neutral. What does each group have in common?

2. Are there obvious differences between the groups?

3. Predict two other substances that will be either acids or bases. We will check some of these later.

TESTING COMMON SOLUTIONS

Which of the

following are acidic or

basic?

GOGGLESGLOVES

LAB COATSHOES

ACTIVITY 5.1 ACID OR BASE? CONTINUED

58CHEMICAL REACTIONS PART 5 ACIDS AND BASES

What to use:


• a selection of coloured plant materials provided by your teacher

• pestle and mortar • 9 test tubes• test-tube rack • chopping board and knife• wash bottle of distilled water• 10 mL measuring cylinder • eye dropper• dropper bottle of hydrochloric acid • dropper bottle of sodium

hydroxide• marking pen.



What to do:

Step 1Construct a table in your Notebook with the headings; plant material, colour in water, colour in acid, colour in base.

Step 2Cut the equivalent of about a 2 cm3 cube of plant material into small pieces on the chopping board.

Step 3Place the material into the mortar with 10 mL water and grind with the pestle until you have a coloured solution.

Step 4Place three test tubes labelled A (acid), B (base) and N (neutral) in the rack. Decant the liquid into the test tubes, dividing it equally between the three tubes.

Step 5Add two drops of hydrochloric acid to tube A, two drops of sodium hydroxide to tube B and two drops of distilled water to tube N.

Step 6Record the results in your table.

Step 7 Repeat Steps 2-6 with two more of the plant materials available.

Discussion:

Hydrochloric acid is an acid and sodium hydroxide is a base.1. Which of the plant extracts do

you think is the best indicator to distinguish an acid from a base? Explain the reason for your choice.

2. Why was distilled water added to tube N?

3. Which would be the best plant extract to distinguish a neutral solution? Explain how you would do this test.

Acid-base indicators are substances that change colour in acidic and basic solutions.Litmus is one, but can other plant materials be used as indicators?

Hydrangea grown in acidic soil.

Hydrangea grown in more basic soil.

DID YOU KNOW hydrangea flowers

change colour in soils

of different acidity?

GOGGLESGLOVES

LAB COATSHOES

59

ACTIVITY TYPE

ACTIVITY 5.2 INDICATORS

CHEMICAL REACTIONS PART 5 ACIDS AND BASES

What to use:


• An extract of the best plant extract indicator

• 6 test tubes• test tube rack• eye dropper• dropper bottles of:• hydrochloric acid• sulfuric acid • nitric acid• sodium hydroxide • potassium hydroxide • ammonium hydroxide.



What to do:

Step 1Construct a suitable table in your Notebook to record your results.

Step 2Divide your indicator between 6 test tubes in a rack.

Step 3In turn, add two drops of each of the acids and hydroxides to the tubes marked 1-6.

Step 4Record your results in the table.

Discussion:

1. Write the formula for each acid and base next to its name in your table.

Do you see anything common to all the acids and all the bases that would make them react differently with the indicator?

2. Group 1 elements are called the alkali metals and Group 2 the alkaline earth metals. Why?

3. Draw diagrams to show the particles in beakers of dilute and concentrated hydrochloric acid and sodium hydroxide.

Teacher demonstration

Your teacher will do some tests to check your reasoning.

WHAT MAKES A SUBSTANCE AN ACID OR BASE?

Water

Water

Water

Water

H+H+

H+H+H+

H+H+H+

OH-

OH-OH-

OH-OH-

OH-

OH-

OH-

Acid

Base

Concentrated Solution Dilute Solution

Volume of the same liquid

More molecules or ions in

concentrated solution compared to dilute solution

Acids dissolve in water to produce hydrogen ions (H+).Example: HCl dissociates (splits) into H+ and Cl- ions.

Bases dissolve in water to produce hydroxide ions (OH-).Example: NaOH DISSOCIATES into Na+ and OH- ions.

A base dissolved in water is called an ALKALI.

If you add more salt to water it dissolves and the solution becomes more concentrated.

If you add more water the solution is diluted, as there are less hydrogen or hydroxide ions in the same volume of solution.

WHAT HAPPENS TO ACIDS AND BASES WHEN THEY DISSOLVE IN WATER?

CONCENTRATED OR DILUTE?

GOGGLESGLOVES

LAB COATSHOES

ACTIVITY 5.2 INDICATORS CONTINUED


What to use:


• 0.1 M hydrochloric acid • 1.0 M sodium hydroxide• 14 test tubes• 10 mL measuring cylinder • dropper bottle of universal

indicator• marking pen• long test-tube rack (or 2 small

racks) • dropping pipette• two mystery

solutions for testing• wash bottle of

distilled water.


• safety glasses.

What to do:

Step 1Label your test tubes 1 to 14.

Step 2Place 10 mL of 0.1 M hydrochloric acid in test tube 1.

Step 3Using the pipette, measure exactly 1 mL of the acid in test tube 1 and transfer it to test tube 2.

Step 4Add exactly 9 mL distilled water to test tube 2 and shake gently to mix.

Step 5Take 1 mL of solution from test tube 2 and transfer it to test tube 3. Add 9 mL of water to test tube 3 and mix as in Step 4.

Step 6Repeat this process until you reach tube 6.

Step 7Place 10 mL of distilled water in test tube 7.

Step 8Measure 10 mL of 1.0 M sodium hydroxide into test tube 14

Step 9Use the pipette to measure exactly 1 mL of sodium hydroxide from tube 14 into tube 13. Add 9 mL distilled water.

Step 10Repeat this process until you reach test tube 8.

Step 11Add 3 drops of universal indicator to each test tube.

Discussion:

1. Which test tubes contain the strongest acid and the strongest base?

2. Refer to the universal indicator chart. What is the pH of: a) the strongest acid b) the weakest acid c) the strongest base d) The weakest base?

3. Which test tube is neutral? What is its pH?

4. Explain what a neutral solution is.

5. What is the pH of your mystery solutions?

MAKE A pH SCALE

stronglyacidic

weaklyacidic

weaklyalkali

stronglyalkalipH neutral

pH scale

1413121110987654321

Indicators change colour depending on the concentration of the acid or alkaline solution. How would you make a 14-point pH indicator scale?

The pH SCALE is used to identify how strong an acid or base is. It indicates the concentration of hydrogen ions in the solution. UNIVERSAL INDICATOR is widely used to measure pH. It is a mixture of different indicators and undergoes a series of colour changes over a range of pH values, from 0 to 14.

CAN YOU WORK OUT:• the dilution between each pH

• the difference in concentration between pH 1 and 3

• the difference in concentration between pH 8 and 11?

GOGGLESGLOVES

LAB COATSHOES

61

ACTIVITY TYPE

ACTIVITY 5.3 THE pH SCALE


Chemical labels of some household substances are missing.Can you discover what they are?

What to use:


• universal indicator paper and colour chart • dropper bottle of unknown household chemical.



What to do:

Step 1Construct a table to record the pH (acid/base/neutral) and your predictions.

Step 2Choose one chemical and find its pH using universal indicator.

Step 3Decide if is an acid, base or neutral substance and predict what it is.

Step 4Repeat for the others.

Discussion:

• Ask your teacher what the chemicals are. Did you predict correctly? What were the clues? What other tests or activities could you do to assist your investigation?

What to use:

Your teacher will distribute containers of household chemicals about the room. Your task is to discover the pH of these substances and what ingredients make them acidic or basic.


• universal indicator paper and colour chart.



What to do:

Step 1Construct a table to record the following information for 10 chemicals: name, chemicals present, prediction (acid/base/neutral), pH.

Step 2Choose one chemical, record its name and information about its contents.

Step 3Predict if it is acidic, basic or neutral.

Step 4Dip a small piece of universal indicator into the chemical. Compare to the colour chart and record the pH.

Step 5Repeat for nine other chemicals.

Discussion:

1. Did you predict accurately? Did any results surprise?

2. List the chemicals tested from the strongest acid to the least acidic (strongest base).

WHAT COULD IT BE?

Mystery solution

A

Mystery solution

C

Mystery solution

B

Mystery solution

D

Now you understand the pH scale, consider some household chemicals. Can you predict if they are acids or bases? What pH do you think they are?

The term pH was first used by the Danish chemist Soren Sorensen in 1909. It means power (p) of hydrogen (H).

GOGGLESGLOVES

LAB COATSHOES

ACTIVITY 5.3 THE pH SCALE CONTINUED


Click here to go to the digital resource Activity 5.3 and learn more about the pH scale.

Your teacher will provide two vinegar

solutions. Find out which is the

strongest.

How would you compare the

concentrations of two solutions

of the same acid?

Can you explain the difference between strong and concentrated and dilute and weak acids?

Use diagrams to illustrate your answer.

IS VINEGAR A WEAK OR STRONG ACID?Weak acids and bases

largely remain as molecules in solutions, so there are

much less hydrogen ions or hydroxide ions present.

Acids in foods are weak acids e.g. ethanoic acid (vinegar);

citric acid and ascorbic acid in fruit; lactic acid in milk.

How could you check vinegar is a weak acid compared to

hydrochloric acid? Discuss with your teacher before testing your idea.

In solutions, STRONG acids and bases dissociate completely into ions.Hydrochloric acid is a strong acid.

HCl H+ + Cl-

Sodium hydroxide is a strong base. Write an equation for its dissociation in water.

WEAK OR STRONG?The same concentrations

of different acids or bases can have different

pH values. How?

Strong acid Weak acid

acid

hydrogen ion

negative ion

undissociated

dissociated

63

ACTIVITY 5.3 THE pH SCALE CONTINUED



What to use:


• dropper bottle of 2 M hydrochloric acid

• dropper bottle of 2 M sodium hydroxide

• dropper bottle of litmus solution (indicator)

• 3 test tubes• test tube rack• wash bottle of distilled water• 10 mL measuring cylinder • Bunsen burner and heating mat• evaporating basin• pipe-clay triangle • tripod stand• metal tongs • matches.



What to do:

Step 1Put small amounts of hydrochloric acid, sodium hydroxide and distilled water into three test tubes. Add one drop of litmus solution and note the colour of the liquid in each tube.

Step 2Add 5 mL sodium hydroxide to a clean test tube with one drop of litmus solution. Note the colour

Step 3Add 1 drop of hydrochloric acid to this test tube. Shake gently and observe for any colour change.

Step 4Repeat Step 2, observing the colour of the solution until the litmus indicator turns purple. This means neutralisation has occurred and you have a neutral solution.

Step 5Set up the Bunsen burner with the pipe clay triangle on the tripod stand.

Step 6Pour the solution into the evaporating basin and place on the pipe-clay triangle.

Step 7Heat gently with a blue flame until the solution is bubbling slowly.

Step 8You will need to control the flame and turn it off before all the water evaporates. This prevents spitting. The remaining heat will complete the evaporation process.

MAKING SALT BY NEUTRALISATION

Now look at the discussion questions on the next page.

What happens to the temperature when you place an acid and base together? Is the reaction endothermic or exothermic?

NEUTRALISATION is an exothermic reaction that always produces water and a salt. The salt produced depends on the acid and base used. The equation shows the reaction between hydrochloric acid and sodium hydroxide. The salt produced is sodium chloride, table salt.

HCl + NaOH H2O + NaCl

acid base water salt (H+ donor) (OH- donor)

The temperature difference when a dilute acid and base are used is difficult to measure with a thermometer. Why? In comparison, reactions between concentrated acids and bases are very dangerous. Why?

Acids and bases react to indicators in opposite ways. How do they react to each other?

GOGGLESGLOVES

LAB COATSHOES

evaporating basin

tripod

bunsen burner

solution

vapour

heat mat

ACTIVITY TYPE

64

ACTIVITY 5.4 NEUTRALISATION


Discussion:

1. What is the solid remaining in the evaporating basin? Why is it coloured?

2. What is the other product of the neutralisation reaction? What has happened to it?

3. The salts produced by hydrochloric acid are called chlorides. What will the salts of sulfuric acid be called?

4. Write word equations for the reactions between:

a) sodium hydroxide and sulfuric acid

b) potassium hydroxide and hydrochloric acid

c) calcium hydroxide and nitric acid.

5. Can you write the formulae for all the compounds above?

6. What kind of bonding occurs in: a) the salt produced b) water?

7. Discuss as a class when your knowledge of neutralisation could be applied to everyday life.

Click here to go to the digital resource Activity 5.4 and find more ideas.

If acids neutralise bases and vice versa, how can they be

used to solve everyday problems?

THINK LIKE A CHEMIST

Using your knowledge of neutralisation and dilution, how would you solve the following problems? What chemicals or approaches would you use?

Choose from: • tomato stains on clothing• relieving a jelly-fish sting• cleaning up an acid spill • improving a garden soil

that is too acidic.

Write a report on your

investigation under the headings:

• Problem - state it in one clear sentence.

• Chemistry - describe the problem’s cause? Is it an acid or

base? • Solution - how would

you solve it? What would you use? Explain any chemical reactions

involved.

65

ACTIVITY 5.4 NEUTRALISATION CONTINUED



Do you remember adding acid to

magnesium ribbon? What was produced

in this reaction?

Many metals react in the same way with acids. The general equation for

the reaction is:

acid + metal salt + hydrogen

What to use:


• dropper bottle of 2 M hydrochloric acid

• 5 cm strip of clean magnesium ribbon

• 3-5 x 1 cm strips of magnesium• dropper bottle of universal

indicator• universal indicator colour chart• 2 test tubes• test tube rack• wooden splint• Bunsen burner to light splint• 10 mL measuring cylinder.



What to do:

Step 1Place 5 mL of hydrochloric acid in a test tube and add three drops of universal indicator. Note the colour.

Step 2Add a 5 cm piece of magnesium ribbon. Invert a second test tube and hold it on top of the reaction tube. Observe what happens.

Step 3Light a wooden splint, then quickly invert the upturned test tube and place the lighted splint just into the top of the tube. What happens?

Step 4What colour is the universal indicator now? Add a 1 cm piece of magnesium. Does the colour change?

Step 5Add more magnesium, 1 cm at a time, until there is no further colour change.What colour is the indicator now?

Discussion:

1. What does the colour of the universal indicator at the start and at the end of the experiment tell you?

2. What type of substance is causing this pH reading?

3. What gas is produced in the reaction? How do you know?

4. Write a word equation for the reaction. Write the formula for each substance under its name.

5. Write a word equation for the reaction you would expect between zinc and sulfuric acid.

INVESTIGATING THE REACTION

The lead terminals become corroded when acid leaking from

the battery forms lead sulfate.

Have you looked under a car bonnet to find the battery?

How can you test for hydrogen

gas?

GOGGLESGLOVES

LAB COATSHOES

HCL

66

ACTIVITY TYPE

ACTIVITY 5.5 ACIDS AND METALS


A fire extinguishers is just one application of the reaction between an acid and a carbonate.

The general equation for the reaction is:

acid + metal carbonate salt + water + carbon dioxide

WRITE A...Individual Report:In your report, ensure you:• Include a graph and inferences from collected data.• Explain any differences in reaction rates.• Discuss whether your hypothesis was correct.• Suggest improvements to your experimental

design.

What to use:


• solid sodium carbonate • dropper bottle of 2 M hydrochloric

acid• test tube with stopper and delivery

tube• test tube half filled with limewater• teaspoon or spatula • 10 mL measuring cylinder• test-tube rack.



What to do:

Step 1Put ½ tsp of sodium carbonate in a test tube.

Step 2Add 5 mL hydrochloric acid. Put in the stopper and delivery tube.

Step 3Use the delivery tube to bubble the gas produced into the limewater.

Discussion:

1. State three observations showing a chemical reaction has occurred.

2. Explain how you can identify the gas produced.

3. Write a word equation for the reaction. Write the formula for each substance under its name.

INVESTIGATING THE REACTION

Chemical reactions produce new chemicals. How can we use acids to make carbon dioxide?

How can you test for carbon dioxide?

O

O

C

O

O

C

O

O

C

O OC

O OC

O OC

Now it’s your turn to design an experiment:

GOGGLESGLOVES

LAB COATSHOES

Your task is to design and carry out an experiment to investigate if the size of pieces of the reacting solid affects the rate of reactions.The experiment is to be written up as a full practical report.

NOTE: Complete the practical work with a partner, but each student must write an individual report.

You will be provided with: • 2 M hydrochloric acid • marble chips (calcium carbonate)• pestle and mortar• test tubes • limewater.

You may use other laboratory equipment with your teacher’s approval.

What to do:Step 1Plan your experiment, considering how to make it a valid and reliable test. How will you compare and measure the speed of each reaction?

Step 2Complete your experiment, recording data as you go. Step 3Write a full practical report.

67

ACTIVITY TYPE

ACTIVITY 5.6 ACIDS AND CARBONATES


How can we distinguish acids and

bases?

Are some foods more

friendly to our stomach?

What acid is produced in your

stomach?

What is reflux? Increasing numbers of people suffer from it. Why? How can we treat it in the short and long terms? What do antacid tablets contain? What are the long-term effects?

Explore these questions with someone in your extended family who has problems with digestion. How do they moderate or control their symptoms? Discuss your findings with the class.

WHAT IS AN ACID?The word acid comes from the latin meaning "sour" (acidus).

Properties of acids include: • a sour taste

• they conduct electricity in solution

• they are very reactive

Can you add more?

WHAT IS A BASE?The terms "base" and "alkali" are often used

interchangeably. "Alkali" is derived from Arabic (al qalı- y) meaning the calcined

ashes, the original source of alkalines.

Properties of bases include: • a bitter taste • they conduct electricity in

solution • a slimy feel

Can you add more?

Click here to go to the digital resource Activity 5.7 and explore properties and applications of acids and bases.

HCl NaOH

68

ACTIVITY TYPE

ACTIVITY 5.7 ACIDS AND BASES EVERYWHERE



Are there better home-made options for

everyday chemicals?

Check labels of household products.

Many have safety warnings as they are poisonous or cause

burns or other injuries. Could we use less-harmful ingredients

for us and the environment?

WRITE A... Have you checked with your teacher that your product is safe to make at home?HINT: Explore the Find out more in the digital resource as a starting point.

Are eco

products as effective?

Your task is to chose a household chemical and make a home-made, non-toxic, substitute. Is it as good as the commercial alternative?

What to do:Step 1Choose a product such as hand cream, bath salts, lip balm, hair gel, window cleaner, shoe polish, mould cleaner…or many more.

Step 2With parent permission, collect all ingredients and make the product at home.

Step 3Design and carry out a fair test to determine if your home-made product works as well as the commercial brand your family uses.

Step 4Write a full report under the correct headings.

Making non-toxic household chemicals: a home-based project.

69

ACTIVITY 5.7 ACIDS AND BASES EVERYWHERE CONTINUED



Click here to go to the digital resource Activity 5.8 and learn more about Penny’s career and consumer chemistry.

Why is it sour? What will make it grow?

Is it good for you? How can we test it?

Each day we answer questions which rely on chemistry knowledge. Can you think of examples?

What will be stronger? How can we make it stick?

For Penny, chemistry is not just a career –

it is her everyday concern as she uses her

knowledge to live healthily and consider

the environment around her.

Meet Penny Frost, growing up on a farm in Grenfell NSW where she appreciated the

importance of land management, food production and healthy eating. Since graduating as

a chemical engineer, Penny has worked in petroleum and wastewater in Sydney, developed

diabetes testing kits in Melbourne and the USA, and helped bring fig and caramel gourmet

ice cream from the hills of Adelaide to supermarket shelves around Australia.

70

ACTIVITY TYPE

ACTIVITY 5.8 ARE YOU A CHEMIST?



From hair colourists to veterinary nurses, scuba divers and dieticians, fireworks, farmers and foodies; a little chemistry knowledge goes a long way. In a group, list as many careers and hobbies you can think of which benefit from chemical knowledge.

71

ACTIVITY 5.8 ARE YOU A CHEMIST? CONTINUEDWhat is

the difference between a chemist,

an industrial chemist and a chemical engineer?


Glossary

Term Description

Acid A substance that dissolves in water to produce hydrogen ions.

Alkali A soluble base is called an alkali.

Alpha radiation Emission of alpha particles (helium nuclei) in a nuclear reaction.

Atom The smallest particle of an element that can take part in a chemical reaction.

Atomic mass The total mass of the protons and neutrons in an atom.

Atomic model A representation to show the arrangement of particles in an atom.

Atomic number The number of protons in an atom.

Background radiation Radiation coming from sources other than that being observed (e.g., cosmic radiation and radiation from unstable isotopes in rocks and soil).

Base A substance that dissolves in water to produce hydroxide ions.

Becquerel The becquerel (Bq) is the unit used to measure the decay rate of radioisotopes. It is the number of atoms that decay per second.

Beta radiation Emission of beta particles (electrons) in a nuclear reaction.

Carbohydrate A large molecule containing only carbon, hydrogen and oxygen (e.g., glucose, starch).

Cathode ray tube A vacuum tube containing an electron emitter and a fluorescent screen to view images produced by the electron beam.

Chemical equation A summary of the reactants and products in a chemical reaction.

Chemical reaction A change that results in new substances being formed.

Classify To sort objects into groups based on their properties.

Combustion A chemical reaction in which a fuel reacts with oxygen to release energy.

Compound A substance made up of two or more atoms joined by chemical bonds.

Covalent bond A force between non-metal atoms due to the sharing of electrons to form molecules.

Covalent compound A compound that is formed by the sharing of electrons between non-metallic elements.

72CHEMICAL REACTIONS GLOSSARY

Glossary

Term Description

Decomposition reaction A chemical reaction in which a compound is broken down into simpler substances.

Electron A sub-atomic particle with a negative charge. Electrons travel in orbitals around the nucleus of an atom.

Electron configuration The number and arrangement of electrons in shells (energy levels) in an atom.

Element A substance made up of only one kind of atom.

Endothermic reaction A chemical reaction which requires energy.

Energy level The energy level of electron orbitals is related to distance from the nucleus; the further away from the nucleus, the higher the energy level of the electrons.

Exothermic reaction A chemical reaction in which energy is released in the form of heat.

Fermentation A reaction in which energy is produced in the absence of oxygen.

Gamma ray Electromagnetic radiation of high energy that can be emitted from radioactive substances.

Geiger-Muller counter An instrument used to measure radioactivity by counting ionisation of particles.

Group A vertical section of the Periodic Table containing elements with similar outer electron configurations.

Haber process An industrial process for the production of ammonia from the elements nitrogen and hydrogen.

Half-life The time taken for half of the radioactive atoms in a sample to decay.

Hypothesis A statement that predicts a possible explanation for observations, that can be tested by experiment.

Incomplete combustion Incomplete combustion occurs if there is insufficient oxygen, so that less energy is produced. The products of the reaction include carbon monoxide and carbon (soot).

Ion A particle that is charged due to the addition or removal of electrons from a neutral atom.

Ionic bond A force between metallic and non-metallic particles due to attraction between positive and negatively charged ions.

Ionic compound A compound formed from metal and non-metal ions.

Ionic solution A solution in which the ions are free to move and conduct electricity.

Isotope An atom of the same element with a different number of neutrons.

Law A theory to which no exceptions have been found at the time it is made. Scientific laws explain why things happen.

Litmus An acid/base indicator obtained from lichens.


Glossary

Term Description

Matter Anything that takes up space and has mass.

Metalloid An element that displays some properties of both metals and non-metals.

Molecular model A model representing the arrangement of atoms and shape of a molecule.

Molecule Two or more atoms chemically combined together in fixed proportions.

Neutral Neither acidic nor basic. A substance with equal amounts of hydroxide and hydrogen ions and a pH of 7.

Neutralisation A reaction between an acid and base that produces salt and water.

Neutron A neutral particle, of equivalent mass to a proton, found in the nucleus of atoms.

Nuclear fission The process where an unstable nucleus splits into two smaller nuclei accompanied by a large release of energy.

Nuclear fusion A nuclear reaction in which two or more atomic nuclei collide at very high speed and join to form a different element, releasing a huge amount of energy.

Nuclear power station A power station in which nuclear energy (fission) is used to produce electricity.

Nucleus The small, dense centre of an atom containing protons and neutrons.

Observation The act of noting, recording and possibly measuring something, often by using an instrument.

Particle An individual piece of matter. Particles include atoms and molecules as well as a variety of even smaller sub atomic entities.

Penetration The ability of radiation to pass through barriers (e.g., paper, aluminium, lead).

Period A horizontal section (row) of the Periodic Table containing elements with the same number of electron shells.

PH scale A scale indicating the hydrogen ion concentration in a solution. It ranges from 0 (strong acid) to 14 (strong base). A pH of 7 is neutral.

Philosopher A person who offers views or theories on profound questions in ethics, abstract concepts, logic and other related fields.

Photosynthesis A series of chemical reactions which occur in the chloroplasts of green plants. Carbon dioxide and water combine in the presence of light and chlorophyll to produce sugars and oxygen.

Polar A polar molecule has positive and negatively charged ends.

Polyatomic ion A charged particle made up of two or more elements that are covalently bonded together and act as one unit (e.g., hydroxide (OH-)).

Precipitate A solid produced in a chemical reaction.

Products The substances produced in a chemical reaction.

Property A feature of a substance that can be used to classify or identify it.

Proton Positively charged particle found in the nucleus of an atom. Each element has a different specific number of protons in its nucleus.


Glossary

Term Description

Radiation The process in which energy is transmitted as particles or waves (e.g., gamma rays, beta particles).

Radioactivity The spontaneous disintegration of an unstable nucleus leading to the emission of radiation.

Radiocarbon dating Radiocarbon dating (or carbon dating) is a dating technique that uses the decay of carbon-14 to measure the age of materials originating from living things (e.g., wood, leather, bones) up to about 60,000 years old.

Radioisotope An atom with an unstable nucleus that decays to form a more stable nucleus of a different element.

Range The distance over which something (e.g., radiation) can be detected or sampled.

Reactants The substances present before a chemical change takes place.

Reagent A substance (reactant) added to make a chemical reaction occur.

Reliability The reliability of an experiment is a measure of its consistency; if repeated the same results are obtained.

Respiration The chemical reactions in which cells obtain energy. Glucose combines with oxygen in a complex series of reactions to produce energy, carbon dioxide and water.

Salt A substance produced in a neutralisation reaction between an acid and a base.

Sievert A sievert (Sv) is the unit used to measure the radiation dose absorbed by the body.

Spectator ions Ions that remain in solution after a precipitate has formed.

Strong acids/bases Strong acid and bases dissociate completely into ions when they are in solution.

Theory An hypothesis that has been supported by repeated scientific testing.

Universal indicator A mixture of different indicators and undergoes a series of colour changes over a range of pH values from 0 to 14.

Valency The combining power of an atom determined by the number of outer shell electrons.

Validity The validity of an experiment is determined by how well the design enables the aims to be achieved. A controlled experiment is valid if all variables that may affect the experiment are controlled and only one factor (the independent variable) is changed.

Weak acids/bases Weak acids and bases largely remain as molecules in solution and so there are fewer hydrogen ions or hydroxide ions present.


Acknowledgements

PeoplePenny Frost (Chemical Engineer), friends and familyLouise Bennetts, Trinity Catholic College, Goulburn

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http://mattson.creighton.edu/History_Gas_Chemistry/Lavoisier.html

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