Acids and Bases: Overview Common Uses of Acids and Bases ...
Demonstrate Understanding of Acids and Bases Science 1.5 (AS90944)
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Transcript of Demonstrate Understanding of Acids and Bases Science 1.5 (AS90944)
Specific Learning Outcomes
Name some common acids and basesUse litmus to identify an acid and describe the
colour changeDefine the terms
◦Element◦Atomic number◦Atomic mass /mass number◦ Isotope
Know names & symbols for first 20 elementsDescribe, draw and label diagrams of atomic
structureUse atomic number and mass number to calculate
the protons, neutrons and electronsDescribe the structure of the periodic table
Specific Learning Outcomes
Write electron configs. in diagrammatic and shorthand form
Use electron config. to identify its periodic groupName and write formulae for common compoundsDescribe how positive and negative ions are formedWrite ion formulae and identify protons, neutrons
and electrons in ionsName and write formula of a range of positive and
negative ionsName and write formulae for a range of ionic
compoundsWrite word and balanced symbol equations for a
range of chemical reactions
Specific Learning Outcomes
Use collision theory to describe how chemical reactions occur
Understand what things affect the reaction rate and how
Name and write the formula for hydrochloric, sulfuric and nitric acids, metal oxides, metal hydroxides, metal carbonates and hydrogen carbonates
Use universal indicator to identify acids and basesUse the pH scale to identify acids and basesDescribe and write balanced equations for a
range of reactions including neutralisation, carbon dioxide formation and salt formation
Common acids and bases
Acids:◦ Taste sour◦ Corrode metals◦ Turn litmus red◦ Universal indicator is red to
green
Bases:◦ Taste bitter◦ Feel slippery◦ Turn litmus blue◦ Are: hydroxides, oxides,
carbonates, hydrogen carbonates◦ Universal indicator is green to
blue
Substance Formula Colour in litmus
Acid or Base
Vinegar CH3COOH
Baking soda NaHCO3
Hydrochloric acid HCl
Sodium hydroxide NaOH
Sulfuric acid H2SO4
Nitric acid HNO3
Washing soda Na2CO3
Red
Red
Red
Red
Blue
Blue
Blue
Acid
Acid
Acid
Acid
Base
Base
Base
Atomic Structure
Atoms are the smallest part of an element that can take part in a chemical reaction
They are made up of:◦Protons (+ve charge)◦Electrons (-ve charge)◦Neutrons (no charge)
Protons and neutrons are found in a central nucleus and contribute most of the mass
Electrons spins rapidly around the outside
Atomic number and mass number
Atoms have two properties:◦ Atomic number – The number of protons (smaller)◦ Mass number – The number of protons plus the number of
neutrons (larger)
Using the above for an example we can find the number of protons, neutrons and electrons in chlorine.◦ 17 protons – the atomic number of the atom◦ 18 neutrons – the mass number minus the atomic number◦ 17 electrons – because the atom is neutral, the number of
protons = number of electrons
Electron Config.
The electrons (same as the protons and atomic number) can be represented diagrammatically or in shorthand form
Using the example from the slide before they would be as follows
or Cl 2, 8, 7
Atomic structure Practice
Complete the table below
Element Symbol
Atomic #
Atomic mass
# proto
n
# neutro
n
# electro
n
Electron
configHydroge
nH 1 1 1 0 1 1
8 8 2, 6
15
32
5
20
Element Symbol
Atomic #
Atomic mass
# proto
n
# neutro
n
# electron
Electron
configHydrogen H 1 1 1 0 1 1
Oxygen O 8 16 8 8 8 2, 6
Phosphorus
P 15 31 15 16 15 2, 8, 5
Sulfur S 16 32 16 16 16 2, 8, 6
Boron B 5 11 5 6 5 2, 3
Calcium Ca 20 40 20 20 20 2, 8, 8, 2
Isotopes
An isotope is different forms of the same element
They are atoms with the SAME number of protons but DIFFERENT numbers of neutrons they therefore have:◦Different mass numbers◦Same atomic number◦Same number of electrons◦Same chemical reactions
Periodic Table
The periodic table shows similarities, differences and relationships between elements
Arranged in rows according to their atomic numberVertical columns = groups
◦ all elements in the same group have the same number of electrons in their outer shell Have similar properties
Horizontal rows = periods◦ Elements in the same period have the same number of
electron shells◦ As you go across a period 1 extra electron is added until the
far noble gases on the right which have 8 (a full outer shell)Metals are on the left and non-metals on the right
Ions and Ionic bonding
Atoms that have lost or gained electron in a chemical reactions are called IONS
Atoms will gain or lose electrons to fill their outer shell and become more stable
A positive ion (cation) will lose electrons leaving it with an overall positive charge
A negative ion (anion) will gain electrons leaving it with an overall negative charge
Eg Sodium (Na), atomic number 11, electron arrangement 2, 8, 1 will lose the one electron to have a full outer shell (the 2nd)
Chlorine (Cl) atomic number 17, electron arrangement 2, 8, 7 will gain 1 electron to have a full outer shell (the 3rd)
Ions 2
Atoms that do not lose or gain electrons are said to be unreactive (the noble gases)
Some ions are made up of more than 1 element eg:◦Hydroxide OH-
◦Ammonium NH4+
◦Nitrate NO3-
◦Hydrogen carbonate HCO3-
◦Carbonate CO32-
◦Phosphate PO43-
Ions 3
Complete the table
Element Electron Config
Lose or gain ele
How many
Ion formed
Config of ion
Lithium 2, 1 Lose 1 Li+ 2
Hydrogen
Fluorine
Aluminium
Sulfur
Potassium
Element Electron Config
Lose or gain ele
How many
Ion formed
Config of ion
Lithium 2, 1 Lose 1 Li+ 2
Hydrogen 1 Lose 1 H+
Fluorine 2, 7 Gain 1 F- 2, 8
Aluminium 2, 8, 3 Lose 3 Al3+ 2, 8
Sulfur 2, 8, 6 Gain 2 S2- 2, 8, 8
Potassium 2, 8, 8, 1 Lose 1 K+ 2, 8, 8
Ionic Bonding
Ions react together in chemical reactions to form compounds
The positive and negative charges need to balance each other out in order to make a stable compound
Eg:
Ionic Table
+1
+2
+3
-1
-2
-3
H+
hydrogen
Mg²+
magnesium
A13+
aluminium
C1-
Chloride
O²-
oxide
N3-
nitride
Na+
sodium
Ca²+
calcium
Fe3+
iron (III)
OH-
hydroxide
CO3²-
carbonate
PO4
-3
phosphate
K+
potassium
Fe²+
iron (II)
NO3
-
nitrate
SO4²-
Sulfate
NH4
+
Ammonium
Cu²+
copper (II)
HCO3
-
bicarbonate
S²-
Sulfide
Zn²+
zinc
Pb²+
lead
Rules for writing and naming ionic compounds
1. Write the positive ion first2. Overall charges must be ‘0’3. Use a subscript number to show the ration
of ions in the compound to remove charges4. Generally ‘ide’ indicates only 1 type of
atom while ‘ate’ indicates an atom combined with oxygen – exception ??
5. When writing formulae with ions involving more than one atom, you must use brackets around the ion
Chemical Reactions
You can tell if a chemical reaction has occurred by…◦Observing changes in
Colour Smell Appearance Temperature Electrical conductivity
◦Noting differences in the physical properties of the reactants and products
◦Testing the chemical appearance of the reactants and products
◦A new product is made
Chemical Reactions
Chemical reactions can occur using different types of reactant. Eg.◦Two different elements
Hydrogen gas and chlorine gas make hydrogen chloride◦A compound and an element
Hydrochloric acid and magnesium makes magnesium chloride and hydrogen gas
◦Two different compounds Copper sulfate and sodium hydroxide make copper hydroxide
and sodium sulfate◦A compound splits into 2 elements
Aluminium oxide turn into aluminium and oxygen ◦A compound splits into 2 compounds
Calcium carbonate makes calcium oxide and carbon dioxide◦A compound splits into an element and a compound
Hydrogen peroxide makes water and oxygen
Chemical equations
A chemical equation is used to summarise what is happening in a chemical reaction
It has reactants on the left and products on the right
These can be written as word equations:
◦Sodium + sulfuric sodium sulfate + Hydroxide acid water
Or Formula equations (these should be balanced)◦2NaOH + H2SO4 Na2SO4 + H2O
Chemical Equations 2
Steps to follow to write a balanced equation
1. Write down the names of the reactants and products
Hydrogen + oxygen water2. Write down the correct formula for the reactants
and products H2 + O2 H2O
3. Balance the equation by putting numbers in front of each reactant and product
2H2 + O2 2H2O
Collision Theory
The particle theory state that all substances are made or particles – atoms, ions or molecules.
Chemical reactions take place when the particles of the reactant collide with one another with sufficient energy to react and form product particles
As the reactants turn into product, the rate of the reaction slows.
Eventually one or both of the reactants are all converted to product and the reaction stops
Reactions of Acids and bases
When ever an acid reacts it forms a salt plus other products
The name of the salt depends on the acid reacting◦Hydrochloric acid ______ Chloride◦Nitric acid ______ Nitrate◦Sulfuric acid ______ Sulfate
Neutralisation
This is the reaction of an acid and a baseIt produces a product with a pH of 7 (neutral)The general reaction is:
Acid + Base Salt + Water
Oxides and Hydroxides is also a neutralisation with the reaction being Acid + Oxide Salt + Water Acid + Hydroxide salt + water
Carbonates or hydrogen carbonates react with acids also but in these reactions Carbon dioxide is also produced Acid + carbonate Salt + Water + Carbon dioxide Acid + hydrogen carbonate salt + water +carbon dioxide