Sciencesecondary 1

Nicco Alyssha Parikh

LABORATORY RULES - do not enter the science laboratory without the teacher’s permission .- No food or drinks are to be consumed in the laboratory.- Do not play/tamper with the equipment .- Keep your desk/working space clean .- Seek permission before carrying out an experiment . - Read all instructions carefully before any experiment - Prepare all apparatus and arrange them such that you will NOT knock them

over .- Wash all apparatus after the experiment and return them to their proper

places .- Dispose waste materials in proper waste bins .- Never throw solids or corrosive liquids in the sink .- Wash your hands thoroughly before leaving the science lab .- Do not remove chemicals and apparatus from the science laboratory .

What is science?

Science is the study of the world around us through observation , experimentation and analysis .

3 main areas of the study in science : Chemistry , Physics and Biology .

These different areas of science may link one another to form other branches of studies such as BIOCHEMISTRY , PHYSICAL CHEMISTRY AND BIOPHYSICS.

Life long skills and attitudes Besides a keen sense of curiosity , a good scientist should

also have the spirit of inquiry .Thus compromises qualities such as keen observation ,

open-mindedness , patience , objectivity , integrity , creativity and perseverance , scientists should be aware of what’s happening around the world . This leads to questioning about what they see and making sense of the data that they collect from their observations . They need to work well with their peers .

The skills of science inquiry – systematic observation , experimentation and analysis.

LABORATORY APPARATUSTEST TUBE

FILTER FUNNEL

BEAKER

CONICAL FLASK

FLAT-BOTTOMED FLASK

RETORT STAND

TRIPOD STAND

EVAPORATING DISH

MEASURING CYLINDER

Liquid holding and filtration

BUNSEN BURNERSource of heat / to raise a flame above the table , high enough for heating.

For supporting apparatus DURING heating

For containing small amounts of chemicals for heating/ for mixing solutions/liquids

For transferring liquid into containers with a small opening ./ For separating solids from liquids by the use of a FILTER PAPER

For containing and mixing chemicals and liquids to produce a gas when heating is NOT required

BELL JAR To separate the set-up of an experiment from the surroundings.

For mixing and heating the chemicals to produces gas when heating IS required .

For supporting apparatus during experiments

To evaporate the liquid IN a solution over a Bunsen burner

To measure volumes of objects

BUNSEN BURNER The yellow colour in a luminous flame is basically from hot particles of soot in the flame . In a blue flame , there are no particles of SOOT to give that incandescent radiation

The difference between a yellow and blue flame depend on the amount of oxygen that is mixed in with the fuel . More oxygen means that the combustion reaction is more efficient and more energy is released . Remember that the more blue the visible light appears , the more energy that light will have

BUNSEN BURNER

The non-luminous flame exists when there is a complete combustion or complete burning process . It happens when there is more than the enough oxygen in the surroundings or in the place where the process will happen.

The temperature of a non-luminous flame is hotter than the temperature of a luminous flame.

FLAMES

1- FUMING FLAME4- CALM FLAME

The scientific method The scientific method consists of main steps a person could take to solve a problem or find out new

things.

Step 1 Make observationsStep 2 Analyse ,infer, predict and hypothesiseStep 3 PLAN experiments to test your hypothesis - record - analyse - conclude Step 4 Record and analyse your results Step 5 DISCUSS with othersStep 6 Summarise your results and draw conclusionsStep 7 Communicate your findings to others

What is technology ?Technology is the application of scientific knowledge for practical

purposes . BENEFITS OF TECHNOLOGY Invention of medicines . Invention of the telephone ,computer, radio and television for

communication and dissemination of information . ABUSES OF TECHNOLOGY Sometimes technology can cause harm to the environment

and society , especially when misused. what do you mean by ‘when misused’? - should you blame the soldiers or the weapons for the lives

lost during battles ? - should you blame the car or the driver for road accidents?

Can technology solve ALL our problems ?

No , although technology has helped us in many ways, it cannot possibly solve all our problems such as natural disasters but however , we can use technology to predict the occurrence of natural disasters though they are not always accurate.

WHERE DO SCIENTISTS WORK?

- Laboratories - Rainforests - Space

Science is not confined to the laboratory but everywhere else too.

Doing field work is going outdoors , away from the laboratory to collect data .

Hazard symbols Explosive Toxic

Flammable Corrosive

Irritable Biohazardous

Radioactive

Substance will react violently when heated or struck

Substance catches fire easily

Substance produces vapours or fumes which irritates the eyes, nose and throat

Substance emits radiation

Substance is harmful in small doses

Substance will eat away other substances

Poisonous substance of a biological nature

Variables In the process of testing a hypothesis , the things that

have an effect on the experiment are called variables , THE INDEPENDENT VARIABLE is the variable you CHANGE.

The variables you DO NOT CHANGE are called CONTROLLED VARIABLES / THE CONTROL. The variable that we measure , which DEPENDS on

the independent variable is called the DEPENDENT VARIABLE .

TIME, RATE AND SPEED TIME is the DURATION OF AN EVENT.

S.I. unit (international system of units) of time is the SECOND and represented by the symbol ‘s’ . Other units of time : MINUTE (min) , HOUR (h) and millisecond (ms) .

Time can also be expressed in terms of days , weeks , months and years.

INSTRUMENTS TO MEASURE TIME

To measure a short period of time ACCURATELY , we use a STOPWATCHTHERE ARE TO TYPES : mechanical and electronic

MECHANICAL STOPWATCH - The mechanical stopwatch has a minute scale and a second scale - The smallest division on the mechanical stopwatch is 0.1 s . Thus the mechanical stopwatch is accurate to 0.1 s .

ELECTRONIC STOPWATCH - The electronic stopwatch/the digital stopwatch is MORE accurate than the mechanical stopwatch .- It can measure time intervals

accurate to 0.01 s ( 2 sig . Fig )

- It can also record time intervals in hours , unlike the mechanical stopwatch

CONVERSION OF UNITS

LENGTHS IN OTHER UNITS what to do? LENGTH IN METERS

30 dm divide 10 = 3 7km times 1000= 7000 2500cm divide 100= 25 32km times 100= 3200 600mm divide 1000= 0.6

74.5 cm divide 100= 0.745

S.I UNITS Prefix Value Symbol

Giga One billion G

Mega One million M

Kilo One thousand k

Deci One tenth d

Centi One hundredth C

Milli One thousandth m

Micro One millionth u

Nano One billionth n

Physical quantity Value Symbol

Length Metre m

Weight Mass Kilogram kg

Temperature Degree celcius Kelvin K

Time Second s

RATE IS AN EXPRESSION OF HOW ONE QUANTITY CHANGES WITH TIME . RATES ARE USEFUL FOR MAKING FAIR COMPRISONS

PHONE CHARGES , INTERNET ACCESS PLANS , BANK LOAN INTEREST RATES AND INFLATION RATES ARE SOME EXAMPLES OF RATES IN REAL LIFE

UNIT AND MEASUREMENTSMEASURING TAPE & METRE RULE

MEASURING TAPE / METRE RULE = measuring short lengths .

METRE RULE = measure to 100 cm (1m)

MEASURING TAPE = FLEXIBLE , SEVERAL METRES , ACCURATE TO 0.1 CM.

VERNIER CALIPERS

Vernier caliper = used to measure Internal and external diameters of cylinder or spherical objects. = have tails that are used to measure depth of narrow tubes = accurate to 0.01 cm

VERNIER CALIPERS

PARALLAX ERROR = Parallax error arises when the position of the eye is not at the same level as the markings to be read .

ZERO ERROR = Zero error in a vernier caliper arises when the zero marking on the main scale does not coincide with the zero marking on the scale , with the jaws if the vernier caliper closed.

VERNIER CALIPERS

Using the Vernier calipers

1) Close the jaws of the Vernier calipers . Ensure that the zero marking on the Vernier scale is in line with the zero marking on the main scale

2) Place the object within the jaws of the Vernier calipers and clamp it firmly in place .

3) Read the length

PARTS OF A VERNIER CALIPER

CHOOSING THE RIGHT INSTRUMENTS

Length to be measured Instruments to be used Accuracy of instrument

Between 0 and 10 cm Vernier calipers To the nearest 0.01 cm

10 cm to 100cm (1m) Meter rule To the nearest mm

5cm and above Measuring tape / contractor’s rule

To the nearest mm ( short lengths )To the nearest cm ( VERY long lengths )

SQUARE GRID Square grid – finding area

4km

4km

Count the ones more than half or half only, as 1 .

1

2

3 4

5

5 x 16= 80

(Not the most accurate way.)

FORMULAS FOR MEASURING AREA AND VOLUME

SQUARE = Length x Length RECTANGLE = Length x Breadth TRIANGLE = ½ x Base x Height CIRCLE = r (square)CUBE = Length x Length x Length CUBOID = Length x Breadth x Height PRISM = Base area x Height = 1/2 x Length x Breadth x HeightPARALLELOGRAM = Base x HeightCONE = 1/3 x x radius2 x heightSPHERE= 4/3 X x radius3

FORMULAS FOR MEASURING VOLUME

PYRAMID = Base area x Height = 1/3 x Length x Length x Height

CYLINDER = Base area x Height = x r(square) x Height

SPHERE = 4/3 r (cube)CONE = 1/3 r(square)Height

MEASURING VOLUME OF LIQUID

Volume of liquid – measured in cm(cube) or litres (1 litre is 1000cmc(cube))

Instruments = MEASURING CYLINDER , BURETTE , PIPETTER AND VOLUMETRIC FLASK

CURVE SEEN AT THE SURFACE OF A LIQUID IS KNOWN AS A MENISCUS . =* To prevent parallax error , the eye must be positioned at the same level as the meniscus

MEASURING MASS

• MASS IS THE AMOUNT OF SUBSTANCE THAT AN OBJECT HAS .

• SI UNIT : KG • MEASURED USING – DOUBLE BEAM BALANCE - ELECTRONIC BALANCE

MEASURING VOLUME OF IRREGULAR SOLIDS

VOLUME OF IRREGULAR SOLIDS CAN BE FOUND USING THE DISPLACEMENT METHOD

- Need a displacement can

VOLUME OF THE SOLID

ELEMENTS e.g) ; ELEMENTS : sucrose solution , ammonia , bromine and protein ;METALS: bronze , copper , mercury

- Oxygen makes up 21% of the atmosphere air .

- An element is a pure chemical substance consisting of one type of atom.

- Magnesium , iron and zinc are grey solids at room temperature .

- Nitrogen makes up 78% of the atmosphere air .

- Copper is a reddish-brown solid.

- Water is made up of the elements hydrogen and oxygen.

- Mercury is a silver-coloured liquid metal that expands evenly on heating.

- Iodine is used as an antiseptic in medicines to prevent infections from wounds (usually purple in colour then to brownish-yellow).

- Metals are usually present in the form of solids at room temperature.

- Hydrogen reacts violently with air and it is said to be explosive .

- Non-metals are usually dull in apprearance .

CLASSIFYING METALS AND NON-METALS

-Elements can be classified as metals and non-metals . (depending on their property)-Except for mercury , all metallic elements are solids at room temperature .-Non-metallic elements exist in solid , liquid and gas .

METALS NON-METALS

Shiny surface Dull surface

Ductile Non-ductile

Malleable Brittle

High melting point Low melting point

High density Low density

Good electrical conductor Poor electrical conductor

Good thermal conductor Poor thermal conductor

Properties

CLASSIFYING ELEMENTS BY STATE

Different elements exist in difference states at room temperature

In the periodic table , there are 11 elements that are in gaseous state , 2 in liquid state and the rest in solid state

PERIODIC TABLE

PERIODIC TABLE

Vertical groups ( SIMILAR chemical properties)Horizontal periods

Metalloids properties are metal + non-metal. They are solids that can be shiny or dull.They conduct heat and electricity better than non-metals but not as well as metals.They are ductile and malleable.

Metal alloy Mixture of 2 or more metals .

GROUPS AND PERIODS

Groups• Columns of elements are called

groups or families. • Elements in each group have

similar but not identical properties.

• For example, lithium (Li), sodium (Na), potassium (K), and other members of group IA are all soft, white, shiny metals.

• All elements in a group have the same number of valence electrons.

Periods• Each horizontal row of

elements is called a period.• The elements in a period are

not alike in properties.• In fact, the properties change

greatly across even given row.

• The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas.

FLOATING AND SINKING

When an object floats on a liquid , the object is less dense than the liquid .

When an object sinks in a liquid , the object is denser than the liquid .

The density of water is 1 g/cm(cube) . An object with a density LOWER than 1 g/cm(cube) will FLOAT on water . An object with a density HIGHER than 1 g/cm(cube) will sink in water

ELEMENTS,COMPOUNDS,MIIXTURES

Electrolysis – break down of substances using electricity

Nitrogen 78%

Oxygen 21%

Carbon dioxide 0.03%

Water Vapour 1%

IN THE EARTH’S CRUST THE 2 MOST ABUNDANT ELEMENTS ARE OXYGEN(47%) AND SILICON (28%)

Poor conductor insulator

PHYSICAL PROPERTIES Strength- is the ability to support a heavy load without breaking or tearing

Transparency – ability of a material to allow light to pass through.

Ductility-is the ability of a material to be drawn into wires without breaking

Hardness –is the ability to withstand scratching by another material

Electrical conductivity-is the ability to allow electricity pass through

Thermal conductivity-is the ability to allow heat to pass through

Malleability-is the ability of a material to be moulded into shapes

Flexibility –is the ability to bend or stretch without breaking

Melting point –is the temperature at which a solid changes into liquid

Boiling point-is the temperature in which liquid changes into gas

Density – refers to mass per unit volume (mass/volume)-mass over volume

PROPERTIES OF METAL ELEMENTSCOPPER - Reddish Brown - Good conductor of electricity - Ductile -Corrosion resistant -Strong

ZINC-Grey solid-Prevents rusting of iron -Good conductor of electricity-Strong -Corrosion resistant

ALUMINIUM-Silvery shiny solid-Low density -strong and light -malleable -corrosion resistant

MERCURY -Silvery liquid -does not react easily with other chemicals -Mercury vapour is fluorescent -Good conductor of heat - Expands evenly of heating

MAGNESIUM-Grey solid-Burns with dazzling light-forms alkali to neutralise excess acid in stomach

IRON-Grey solid-Good conductor of heat and electricity-Ductile-strong-Magnetic

PROPERTIES OF NON-METAL ELEMENTS

IODINE-Black crystals-poisonous-antiseptic-prevents wound infection

CHLORINE-greenish-yellow gas-bleaches dyes-poisonous

SULPHUR-yellow powdery solid-poisonous-soluble in organic solvent (alcohol) but not in water

DIAMOND(CARBON)-hardest substance known to man -can be polished to shiny , reflecting , transparent solid

HYDROGEN-colourless gas-gas with lowest density -explosive

CARBON (GRAPHITE)-black solid-smooth -lightweight -good conductor of electricity

PROPERTIES OF NON-METAL ELEMENTS

OXYGEN-colourless gas- Essential for life- Does not burn but

supports combustion (allows other things to burn)

NITROGEN-colourless gas-unreactive , does not burn or support combustion -low boiling point

WHAT ARE COMPOUNDS?

When different elements are chemically combined together , they form new substances known as compounds.

e.g: Hydrogen + Oxygen = water (compound ) Sodium + Chloride = table salt (compound) Carbon + Hydrogen + Oxygen = sugar (compound) Calcium + Carbon + Oxygen = chalk (compound)

CHARACTERISTICS OF COMPUNDS

To form water the ratio of hydrogen and oxygen that combine chemically is always 1:8 .

HOW ARE COMPOUNDS FORMED?Made of elements , other compounds , both elements and compounds – FORMED BY CHEMICAL REACTION

- 2 main methods of forming compounds : COMBINATION : DECOMPOSITION (heated to break down )

Combustion

BREAKING DOWN

CHEMICAL BREAKDOWNS heating electrolysis photolysis Involves breaking of chemical bonds

PHYSICAL BREAKDOWN physically breaking . (E.g.) tearing , chewing …) QUESTION

physical/chemical separation . ?

COMBINATION

One common example of combination is combustion . THIS HAPPENS WHEN ELEMENTS OR COMPOUNDS BURN AND COMBINE WITH OXYGEN TO FORM ONE OR MORE NEW COMPOUNDS .

Eg.) carbon + oxygen = carbon dioxide

DECOMPOSITION

Decomposition occurs when 2 or more complex compounds are heated to break them down into simpler compounds.It decomposes to form water vapour and carbon .

E.G ) sugar (compound) Water vapour ( compound) + Carbon ( element )

BREAKING DOWN

Some compounds can be broken down into simpler substances when EXPOSED TO LIGHT . For example CFC ( CHLOROFLUOROCARBON ) compound is Styrofoam is broken down by sunlight into a hazardous substance . THIS SUBSTANCE DEPLETES THE OZONE LAYER .

MIXTURES

Properties of Mixtures :When a mixture is formed , no chemical reaction occurs .A MIXTURE HAS THE PROPERTIES OF ITS CONSTITUENT SUBSTANCES .A mixture can be separated easily by physical methods (i.e. without involving chemical reaction).The components in mixtures are not mixed in any fixed proportion.Water bath is to ensure gentle and even heating .

DIFFERENT KINDS OF MIXTURES

Solid-solid ( Alloys )Liquid-Liquid ( Vinegar)Solid-Liquid ( Lotion )Liquid-Gas ( Foam )Gas-gas ( air )

MAGNETIC ATTRACTION

Used to separate magnetic materials from non-magnetic materials .

Separating iron from sulphur

USES OF MAGNETIC ATTRACTION- Food processing - To salvage scrap iron and steel

FILTRATIONBAKERS MUST USE A SIEVE TO REMOVE LUMPS FROM THE FLOUR MIXTURE.

Filtration works by allowing small liquid particles through , but not large solid particles.

The filter paper has tiny pores that allow the liquid component to pass through it . The insoluble liquid solid particles that are too large to pass through it . The insoluble liquid is called the residue and the liquid that passes through the filter paper is called the filtrate .

EVAPORATION

Evaporation(to dryness ) is used to separate a dissolved solid from a liquid . The dissolved solid must be stable to hear and NOT decomposes .

When the mixture has completely evaporated , no water is left behind . The solid salt left behind as the RESIDUE.

DISTILLATION

Distillation is used to separate a pure liquid from a solid-liquid or a liquid-liquid mixture . The pure liquid collected from distillation is called the distillate .

condensation

Vaporization

condenser

Ensure heating is gentle (water bath)

DESALINATION PLANTS

Desalination is a treatment process that removes dissolved salts from sea water to obtain pure water . Distillation is one of the traditional methods used to carry out desalination .

FRACTINAL DISTILLATIONGas – high temperature & HIGH KINETIC ENERGY .

Fractional distillation also depends on the difference in the boiling points of different liquids .

Crude oil is a mixture of liquids with different boiling points . Oil refineries use fractional distillation to separate crude oil into useful products such as petrol , diesel , kerosene

SEPARATE CREAM AND MILK AS MILK IS SOULUBLE IN CREAM.

PAPER CHROMATOGRAPHY

Separation methods like filtration and distillation require a large amount of the mixture to be separated .

This is usually used to separate mixtures of coloured substances such as ink and dyes.

Paper chromatography makes use of the fact that different paces . Similarly , different substance move through particular mediums at different rates.

Paper chromatography makes use of the fact that different substances dissolve to different extents in a mixture .

REVERSE OSMOSIS In reverse osmosis , sea water is pre-treated to remove debris and contaminants such as oil , grease and suspended solids . The pre-treated sea water is then pumped at high pressure through partially-permeable membrane to remove all traces if bacteria , viruses , chemicals and dissolve minerals .

WATER MOLECULES

What is reverse osmosis?

Reverse osmosis (RO) is a membrane-technology filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective," this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as the solvent) to pass freely.

NEWaterTOWARDS A SUSTAINABLE WATER SUPPLY

• NEWater currently meets 30% of Singapore’s total water demand.

• NEWater is high-grade reclaimed water produced from treated used water that is purified further using advanced membrane technologies, making the water ultra-clean and safe to drink.

• The second stage of the NEWater production process is known as Reverse Osmosis (RO). In RO, a semi-permeable membrane is used.

• Consequently, undesirable contaminants such as bacteria, viruses, heavy metals etc., cannot pass through the membrane.

• Hence, NEWater is RO water and is free from viruses, bacteria and contains negligible amount of salts and organic matters.

GENERAL QUESTION

DESCRIBE and EXPLAIN how you would separate a mixture of sugar and chalk . (4 marks)

Add water to the mixture (1/2 mark) and stir well to mix (1/2 mark) . This dissolves the sugar (1/2 marks) to form a sugar solution (1/2 marks) . Carry out filtration(1 mark) . Separate sugar solution and chalk . The residue is the chalk and the filtrate is the sugar solution (1 mark).

SOLUTIONS AND SUSPENSIONSWhat are solutions ?Solutions are mixtures in which soluble particles are completely dissolved in a liquid or gas.

HOMOGENEOUS : same throughout BUBBLES : pocket of air

What are suspensions? Suspensions are mixtures in which insoluble particles are suspended in a liquid or gas .

What is solubility ?Solubility is the maximum amount of solute that can dissolve in 100grams of solvent at a given temperature .

SOLUTE , SOLVENT AND SOLUTION

The solute is the substance that dissolves in a solvent .

The solvent is the substance that dissolves in the solute .

The solution is the mixture of the solute and solvent .

CHARACTERISTICS OF A SOLUTION

Homogeneous

When left on it’s own , the solute does not separate from the solvent .

When filtered , no residual particles will remain on the filter paper . It will pass through completely .

SUSPENSION

It is the exact opposite of a solution .

A SUSPENSION IS A MIXTURE IN WHICH INSOLUBLE PARTICLES ARE SUSPENDED IN A LIQUID OR GAS .

SOLUBILITY

Factors that affect solubility _ nature of the solvent _nature of the solute _temperature

RATE OF DISSOLVING

• The rate of dissolving is how fast a substance dissolves in a fixed volume of solvent .

TEMPERATURE

RATE OF STIRRING

SIZE OF SOLUTE PARTICLES

ACIDS AND ALKALI

Adjectives : acids- acidic alkali-alkaline

Solutions can be sorted by whether they are: acid, alkali or neutral.

ACIDS

ALKALIS

SOUR BITTER

CORROSIVE CORROSIVE

TURNS BLUE LITMUS PAPER RED

TURNS RED LITMUS PAPER BLUE

NOT SLIPPERY SLIPPERY (SOAPY FEEL )

CONCENTRATED VS SATURATED

Concentrated acids / alkalis

Concentrated – amount of substance variable

Saturated – maximum amount of substance in the medium environment .

ACIDS• Acid are soluble in water produce hydroxide

ions – OH(when dissolved in water)When the oxide of some non-metals dissolve in water they make an acid. Acids have a sour taste.

They are corrosive

Hydrochloric acids Used to remove rust on iron and steel

Sulphuric acids Used in car batteries , Remove rust from steel objects , makes fertilisers .

Nitric acid used to manufacture fertilisers

REACTION OF ACIDS WITH METALS AND CARBONATES

Acid + carbonate salt + water+ carbon dioxide

Formed by chemical reaction

Metal + Acid Salt + Hydrogenmagnesium + magnesium chloride

hydrochloric acid hydrogen

ACIDS IN OUR DAILY LIVES

Acids are also present in everyday lives

Lemon juice contains citric acid, and vinegar contains ethanoic acid.

Some strong acids are hydrochloric acid, sulphuric acid and nitric acid.

Some weak acids are ethanoic acid, citric acid and carbonic acid.

NEUTRALISATION

Acids and alkalis react with each other. The alkali cancels out the acid in the reaction. This is called neutralisation.

SALT is made when from chemical reaction.

NEUTRALISATION IN EVERYDAY LIVES

Face tonersFace cleansersShampoosConditionersToothpasteInsect stings

CHEMICAL REACTIONS OF ACIDS1)Acid + Metal salt + hydrogen gas

2) Acid + Carbonate salt + carbon dioxide gas + H2O

3)Acid + Alkali salt + water

*** limewater(slake lime) will turn cloudy , white precipitate produced .

Not all metals react with acids (unreactive) Some are very reactive *Hazardous and explosive*

Hydrochloric – very strong acid ( CONCENTRATED )

*potassium + hydrochloric acid => vigorous

SALTS

The salts of sulphuric acid are known as sulphates. The salts of hydrochloric acid are known as chlorides. The salts of nitric acid are known as nitrates.

• The salt made depends on the acid and alkali used. • The salt contains the metal atom from the alkali,

and part of the acid molecule. • Reaction of salt with water is known as salt

hydrolysis

ALKALIS

Many everyday substances are alkalis. They have a soapy feel (slippery). They are corrosive.

When the oxides of some metals dissolve in water they make an alkali solution.

Alkalis react with acids and neutralise them.

ALKALIS IN OUR DAILY LIVESAlkalis are present in many cleaning substances in use in our

homes. Kitchen cleaners are alkaline because they contain ammonia

or sodium hydroxide, which attack grease.The PH of alkali is greater than 7.

Calcium hydroxide and sodium hydroxide are strong alkalis. The most recognisable and common weak alkali is ammonia.

Ammonia reacts with ammonium salt to produce ammonia gas

INDICATORS Indicators help you find out whether a solution is acidic or not.

They change colour in acid or alkaline solutions.

All indicator are weak alkaline or weak acid the colour of indicator is due to ionic part of indicator.

Different indicators change to

different colours.

LITMUS PAPER

• Litmus is an indicator. It changes colour in acid and alkaline solutions.

• Different indicator show different colour.• Litmus paper is red in an acid. (Acids turn blue

litmus paper red)• Litmus is blue in an alkali.(Alkalis turn red

litmus paper blue)

pH SCALE (INDICATORS)

Acids less than 7Alkalis more than 7 7 is neutral The lower the number for acids , the stronger the acid . The higher the number for alkalis , the stronger the alkali .

REVISION OF ACIDS AND ALKALIAcids : Corrosive Sour Reacts with blue litmus paper Turns blue litmus paper red Dilute sulphuric acid + magnesium = magnesium sulphate + hydrogen Dilute hydrochloric acid + magnesium = magnesium chloride + hydrogen Dilute acid + Metal = salt + hydrogen Effervescent => bubbly Citric : lemon Formic acid : Insect stings Lactic acid : milk Acid reacts with carbonates to give off carbon dioxide gas Calcium carbonate + dilute sulphuric acid = calcium sulphate + carbon dioxide + water Dilute acid + carbonate = salt + carbon dioxide + water( only with carbonates) Sulphuric acid = in car batteries Nitric acid = in fertilisers Hydrochloric acid = take out rust Dilute acid + carbonate salt + carbon dioxide + water

ALKALI

Bitter Corrosive Soapy feelTurn red litmus paper blue Ammonia : fertiliser maker Sodium hydroxide (caustic soda ) => detergents Calcium hydroxide ( slaked lime/limewater) =>

reduce acidity in soil in agriculture

Neutralisation

Sodium hydroxide + hydrochloric acid = sodium + water Acid + Alkali = Salt + Water Water : H2O

EVERYDAY LIVES NEUTRALISATION ( reduces acidity/alkaline)TonersShampoos , conditionersToothpaste

(mentos and coke )

Indicator

PH SCALE / RED OR BLUE LITMUS PAPERChanges colour depending on solution tested(acid

or alkali ) : definition 0-------------7-----------------14

Water = neutral ( PH 7 )

Acid neutral alkali

HEAT AND IT’S EFFECTS• EXPANSION (GAINS HEAT ENERGY )• CONTRACTION (LOOSES HEAT ENERGY )

Countering expansions LEAVING GAPSSolids Expands very little (particles are joined) Liquids Expands more than the solids but less than the gases (More particles than gases and a near each other)Gases Expands most ( Very little particles and are spread freelyBrass contracts/expands more than steel

EXPANSION AND CONTRACTIONSOLIDS Solids expand when heated and contract when cooled . However , some solids expand so little that we may not even notice the expansion .

Liquids If the kettle is filled to the brim with water , the water will spill out when it boils because water expands when heated and contracts when cooled.

Gases Before a loaf of bread is baked, thousands of tiny air bubbles are trapped inside the dough . As the dough is heated, these bubbles gain heat and expand, creating holes in the bread . This causes the bread to rise . Gases expand when heated and contract when cooled

ROADS AND PATHWAYS(-ve)

Excessive expansion on very hot days can cause roads or pavements to crack , or tiles pop-out . To get around with this problem , the tiles on pavements and walls are laid with EXPANSION GAPS

BRIDGES AND METAL GIRDERS

Long bridges sometimes expand up to a meter in hot weather . Without allowance for expansion , such structures are at risk of damage in very hot weather . Bridges and metal girders on buildings have EXPANSION GAPS or a free end resting on rollers to allow expansion .

* ROLLERS ALLOW BRIDGES AND GIRDERS TO EXPAND OR CONTRACT WITHOUT DAMAGE

WATER PIPES

Water pipes and oil pipelines can expand during hit weather , which might cause them to BURST . Hence , EXPANSION BENDS are made in these pipes to allow them to expand without any damage

* Expansion bends help prevent damage to pipes

TELEPHONE WIRES AND CABLES

Telephone wire and cables raised on poles contract in cold weather and become taut , and may even snap. So , they are STRUNG LOOSELY from pole to pole to allow contraction .

*Transmission wires must be strung loosely from pole to pole to allow contraction during hot weather.

LABORATORY GLASSWARE

If boiling water is poured into a thick glass , the glass is likely to crack due to the uneven expansion of the glass . ( THE CG(center of gravity)OF THE GLASS IS THE AREA WITH HIGHEST GRAVITY , with too much of it at the top , the glass will TOPPLE).

COUNTERING glassware expansion use of borosilicate / heat-resistant glass.

METAL TYRES(+ve)

A metal tyre can be heated up to fit over a wooden wheel . When the tyre cools , it clings on very tightly to the rim of the wheel .

heat

RIVETS

Rivets are used to join steel plates and girders.1) When red-hot , the rivet is put into position2) It is then hammered into a head and allowed

to cool.3) The contraction on cooling helps to pull the

steel together.

BIMETALLIC STRIP

rivets

brass

THE BRASS EXPANDS MORE (BECOMES BIGGER) than the steel when HEATED . SO , when heated , the strip bends with the brass on the outside of the curve.

WHEN COOLED , the brass contracts more ( BECOMES SMALLER ) than the steel . Hence , the strip bends with the steel on the outside if the curve .

BRASS AND STEEL

Steel = iron + carbon

Brass = zinc + copper

* THESE ARE BOTH METAL ALLOYS ( consists of two or more metals )

USES OF A BIMETALLIC STRIP

• THERMOSTAT keeps temperature constant : regulates the temperature (HOT/COLD)

*examples : used in refrigerators , ovens , air-conditioners.

Bimetallic strips are used in thermostats .

BIMETALLIC STRIPS

Cooling takes place when the temperature is too cold . The strip bends away to break the contact

Heating takes place when the current is on . When the temperature is too hot , the strip bends away to break the contact .

IN THE REFRIGERATORCOOLING hotter : connected colder : not connected

HEATING Cold air stops blowing , refrigerator heats up

CONTRACTION -Pulling (inwards)

CONDUCTION

• Heat moves from a hotter region to a cooler region .

• Conduction is the process of heat transfer through a medium or material without any movement of the medium or material

A material that conducts heat are called CONDUCTORS but those that do not conduct heat are called INSULATORS

GOOD CONDUCTORS OF HEAT

Most metals are good conductors of heat . However , some conduct better than others . The higher the THERMAL CONDUCTIVITY of a material , the better it conducts heat.

CONVECTION Convection is the transfer of heat from one place to another by the movement of fluids . A fluid with a given density rises within a fluid of greater density and sinks within a fluid of smaller density.

Convection takes place due to the expansion of fluid. When the fluid (i.e. a liquid or gas ) is hot , its volume increases . This means its density decreases . The less dense fluid then rises and floats while the denser fluid flows in to take its place.

USES AND EFFECTS OF CONVECTION

Household ventilation

Hot air rises and collects under the ceiling . A cool room has features that let hot air out and cool air in. HOT AIR RISES , COLD AIR SINKS . If there are no air vents , we can use an air conditioner to keep the room cool.

1) The hot air in the room rises to the ceiling 2) The air-conditioner cools the hot air , which then sinks to the

bottom of the room.3) More hot air rises and is cooled by the air-conditioner . The

cycle repeats itself until the room is cooled .

ELECTRIC KETTLE

What happens if the heating coil of an electric kettle is placed near the top of the kettle ?

If the heating coil is placed near the top of the kettle , the water near the top will start to boil while the other parts of the water will remain cool . There will be no circulation of heat .

LAND AND SEA BREEZESLand and sea breezes are caused by convection . (Water us a poor conductor of heat) . During the day , the land is hotter than the sea . Hot air rises from the land and cool sea breezes blow in to take its place . At night , the reverse takes place . The sea retains its heat and land cools faster.

Convection : Mode of heat transfer Convection current : Current flow of heat

RADIATIONRadiation is the method of heat transfer that

does not require the presence of matter .. Here from the sun radiates across millions of kilometers of empty space . The heat that comes by radiation is carried by light waves from the sun invisible infrared and visible light . This heat is sometimes called radiant heat.

RADIATION Radiation is the transfer of heat , in the form of waves (heat waves) , from one place to another without a medium .

HOW A BODY RADIATES HEAT

1) Nature of the surface of the body (whether it is black or white or coloured , rough or smooth or shiny )The darker and rougher the surface , the more heat it gives out per

second .2) Total surface area of a body The greater the area , the more heat per second is radiated. 3) Temperature of the body The hotter the body temperature , the more heart per second is radiated .

Why is it windy at the seaside?

Cold air sinks

Where is the freezer

compartment put in a fridge?

Freezer compartment

It is put at the top, because cool air sinks, so it cools the food on the

way down.

It is warmer at the bottom, so this warmer air

rises and a convection

current is set up.

Radiation

Radiation travels in straight lines

True/False

Radiation can travel through a vacuum

True/False

Radiation requires particles to travel

True/False

Radiation travels at the speed of light

True/False

Emission experiment

Four containers were filled with warm water. Which container would have the warmest water after ten minutes?

Shiny metal

Dull metal

Dull black

Shiny black

The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation.

shiny metal

radiation

dull black

emitting

Factors Affecting Radiation

1. Nature of surface of body2. Total surface area of body3. Temperature difference

between the body and its surrounding

113

Vacuum Flask

Radiation questions

Why are houses painted white in hot countries?

White reflects heat radiation and keeps the house cooler.

Why are shiny foil blankets wrapped around marathon runners at the end of a race?

The shiny metal reflects the heat radiation from the runner back in, this stops the runner getting cold.

Convection questions

Why are boilers placed beneath hot water tanks in people’s homes?

Hot water rises.

So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.

Why does hot air rise and cold air sink?

Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air.

1. How does heat energy reach the Earth from the Sun?

A. Radiation

B. Conduction

C. Convection

2. Which is the best surface for reflecting heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

3. Which is the best surface for absorbing heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

1201

Chemical Changes

GLOW STICK

Has a glass vial inside the plastic tubeBending the light stick causes the glass vial to

breakThe two solutions mix and undergo a reaction

called chemiluminiscene , light is emitted .

122

What are the changes that can take place?

Physical changes Chemical changes

123

Definition of chemical Reaction

• Chemical changes are permanent and irreversible

• Produced new substances• Reactants are changed into products

Example: reactant A + reactant B product C +

product B

124

Definition of physical reaction

• When a change is reversible, we call it a physical change

• No new substance is formed

PROCESSESBurning bottled gas for outdoor cooking Combustion Iron rusting in the presence of water and oxygen Combination Sugar being heated strongly Decomposition Water being broken down into its elements by electricity Electrolysis Water puddle slowly disappearing under sunlight Evaporation

126

Differences between physical and chemical changes

Physical Changes Chemical Changes

No new substances formed New substances are formed

No or little heat is taken in or given out

Heat and/or light energy may be taken in or given out

Properties of substance do not change

Properties of products different from starting reactants

127

between matter and different forms of energy:

1. Heat

2. Light

3. Electricity or by

4. Combination of 2 different matter

Physical & chemical changes are brought about by interactions

128

1. Changes in State of Matter

2. Combination

3. Thermal Decomposition

4. Combustion

Chemical Changes Caused by Heat

129

Heat Causes Changes in the State of Matter

• From Solid to liquid to gas or vice versa• Melting, freezing, boiling, evaporation• Sublimation: From solid change straight to gas

These are physical changes since changes are reversible and no new products are

formed

130

• Some substances undergo sublimation • Like dry ice (carbon dioxide) and iodine

SUBLIMATION

131

Combination

• Combination refers to a process in which two or more substances form a new substance

ExampleIron + Sulphur Iron Sulfide

Fe + S FeS

heatheat

132

Combination

2K + Cl2 2K2Cl

133

Combustion

• Refers to combination of a substance with oxygen in the presence of heat.

• One or more new substances may be produced

134

• Can combustion take place on the moon?• No, unless there is a supply of air or

oxygen present

CombustionCombustion

135

Combustion = BurningCombustion = Burning

136

• Processes such as rusting and combustion are oxidation reactions.

• Oxidation refers to a process in which a substance reacts with oxygen

Combustion is a type of oxidation reaction Combustion is a type of oxidation reaction

Oxidation

• Examples- Burning of magnesium in oxygen- Rusting of iron- Fireworks- Burning of paper or wood

Burning Mg

Rust

138

Thermal Decomposition

• A substance breaks down into 2 or more substances by effect of heatExample:

sugar carbon + water vapour

calcium carbonate calcium oxide + carbon dioxide

heatheat

heatheat

139

Decomposition

140

Chemical Changes Caused by Light

• Photosynthesis• Photography• Obtaining energy from solar cells

141

Chemical Changes Caused by Light• Photosynthesis:

Process in which green plants make food in the presence of light

carbon dioxide + water glucose + oxygensunlightsunlight

chlorophyllchlorophyll

Chemical Changes Caused by Light

143

Chemical Changes Caused By Light

Under the exposure of light, chemical reaction takes place with the formation of new productsUnder the exposure of light, chemical reaction takes place with the formation of new products

Fading of the colour of newspaper due to light

exposure

144

Chemical Changes Caused By Light

Example

photographic films : coating of silver bromide

silver bromide silver + bromine

Example

photographic films : coating of silver bromide

silver bromide silver + brominelight

145

Chemical Changes Caused By Light

• Does chemical changes take place if a digital camera is used?

• No, light is changed to electrical signals to form images in a digital camera.

146

• Solar cells are also called photovoltaic cells

• They convert light energy directly into electricity

Chemical Changes Caused by LightChemical Changes Caused by Light

Solar Cells

Solar Panels on House Roof

Solar cells are used in areas where electricity is not readily available.

Suggests some uses of this energy within the house.

148

Electricity

The changes that takes place include:• Heating• Light production• Magnetic effect• Chemical effect• Electrolysis

Heating a light bulb with electricity to produce light

• A physical process• The filament in the light bulb is heated up,

and electrical energy is converted to heat and light energy. No new substances are formed

149

Splitting water using electricity

• This process is called Electrolysis (breaking down of substance using electricity )

151

Chemical Changes Caused By Mixing

Sodium hypochlorite + water chlorine gas (bleaching)

Also used in swimming pools:

LIGHT CAN BE USEFUL TO US (3 WAYS)

Photosynthesis — plants use light to make food,

which in turn gives us food.

Photography — light causes chemical changes on photographic film, giving us photographs.

Obtaining energy from solar cells — light is

converted into electricity.

DIFFERENTIATING Process Change Cooking meat Chemical Extracting aluminum from aluminum ore Chemical Boiling water Physical Photosynthesis Chemical Exposing photographic film to light Chemical Iodine crystals turning into iodine gas Physical

USEFULNESSUSEFUL NOT USEFUL

Photosynthesis Rusting

Combustion of fuels in power stations Combustion of fuels producing air pollutants

Respiration Forest fires

Decay of dead organisms

Extracting iron from ore

Making electromagnets electroplating

digestion

IMPORTANCE OF CHEMICAL CHANGE

Why is the decay of dead organisms an important and useful chemical change? It returns nutrients back to soil to be recycled for use naturally by plants, otherwise dead organisms would be found everywhere and there would not be enough space on earth to bury them.

ENERGY CHANGES AND HOW THEY WORK

i) Furnace --Chemical energy in fuel is changed to heat by combustion.

ii) Boiler -- Heat causes the water particles to have more kinetic energy and turns into moving steam, which has kinetic energy.

iii) Turbine --The turbine transfers kinetic energy of the moving steam to the generator.

iv) Generator --Kinetic energy from the turbine turns the generator. Kinetic energy of the generator is changed to electricity.

DEFINITIONS

SUBLIMATION - Thermal exothermic (give out / release)- endothermic (take in ) OXIDATION- Refers to a process in which a substance reacts

with oxygen - Processes such as rusting and combustion are oxidation reactions .

SOLID

GAS LIQUIDM

ELTING

BOILING(1000C) / EVAPORATION

SOLI

DIFI

CATI

ON

/FR

OST

FORM

ATIO

N

FREEZING

CONDENSATIONSU

BLIM

ATIO

N

FILMS VS DIGITAL

Light rays that have bounced off the object and entered the lens of the camera . The source of light is the light shining on the films and images will be imprinted on the film due to light (reacting with silver bromide) .

FILMS VS DIGITAL

FILMS [CHEMICAL CHANGE] Light energy (from objects) converted into electrical energy.

DIGITAL [PHYSICAL CHANGE]Electrical signals

SOLAR CELLS

• In calculators • Use photovoltaic cells (in photography)

They convert light energy directly into electricity

LOMOGRAPHY Coloured films

GLOW STICK

Has a glass vial inside the plastic tubeBending the light stick causes the glass vial to

breakThe two solutions mix and undergo a reaction

called chemiluminiscene , light is emitted .

MATERIALS

• Grouping and sorting is called classification.• Grouping of objects always helps us to do our

work efficiently .• Classification of objects can be based on

similarities and differences . • NON-LIVING THINGS AND LIVING THINGS• MAN-MADE AND NATURAL• Metals, glass , ceramic , plastic , fibre

METALS

• Cobalt• Nickel • Iron

They have natural ores . Gold , silver … have ores too!

Loadstones

COPPER OREPlatinum ore

Lead ore