C2 Chemistry
Additional Science
Key Recall
Questions
*Cover up the answers, ask yourself a question (or get your partner to ask you), if you get it
right then tick the chart, wrong put a cross. Keep practising until all columns are ticked!
Key terms
Key Recall Question
1. What is a particle?
2. What is an atom?
3. What is an element?
4. What is a mixture?
5. What is a compound?
6. What is a molecule?
7. What are the reactants of a chemical reaction?
8. What are the products of a chemical reaction?
9. Why is it important to show chemical reactions
with an arrow?
10. What are the four state symbols used in chemical
reactions and what do they mean?
Answer
A general word used by scientists to mean small
part of matter (something)
The smallest particle that can be recognized as an
element. If you break an element into its smaller
pieces you can no longer recognize that it is an
element.
A substance that is composed of only one type of
atom.
Substances which are together (in the same space)
but not chemically joined.
Substances in which atoms of two or more
elements are chemically combined.
A word to describe atoms which are chemically
joined together. These might be two of the same
type of atoms (an element molecule) or two or
more different types of atom (a compound
molecule)
The substances which react together in a chemical
reaction
The substances which are produced as a result of a
chemical reaction
The arrows shows ‘reacts to make’ and signifies
that the reactants have been chemically changed
into products and cannot be (easily) reversed
Solid (s), Liquid (l), Gas (g) and Aqueous (aq) which
means dissolved in water
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C2.1 Structure and bonding_1
Key Recall Question
1. What is a compound?
2. What are the two ways chemical bonds achieve
the electronic structure of a noble gas?
3. What do atoms become when they form chemical
bonds by transferring electrons?
4. What charge do ions have when the atom which
formed them lost an electron?
5. What charge do ions have when the atom which
formed them gains an electron?
6. What charge do ions have when they are formed
from an element in group 1?
7. What charge do ions have when they are formed
from an element in group 7?
8. What charge do ions have when they are formed
from an element in group 2?
9. What charge do ions have when they are formed
from an element in group 6?
10. Which group of elements do not form ions?
Answer
Substances in which atoms of two or more
elements are chemically combined.
They transfer or share electrons in the highest
occupied energy levels (shells)
Ions
Positive (+)
Negative (-)
+1
-1
+2
-2
Group 0 (noble gases)
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C2.1 Structure and bonding_2
Key Recall Question
1. What type of electron structure do ions have?
2. What are the elements in group 1 known as?
3. When they react with non-metals, what charge
does the metal ion have in the ionic compound
formed?
4. Can you name any elements in group 1?
5. What are the elements in group 7 known as?
6. When they react with alkali metals, what charge
does the halide ion have in the ionic compound
formed?
7. Can you name any elements in group 7?
8. How are ionic compounds formed?
9. What is an ionic lattice?
10. What is the name of the ionic compound formed
when sodium and chlorine form ions?
Answer
The electron structure of a noble gas
Alkali metals
A single positive charge
Lithium, sodium, potassium, rubidium, caesium,
francium (it is important that you at least know
sodium is a group 1 element)
Halogens
A single negative charge
Fluorine, chlorine, bromine, iodine, astatine (It is
important that you at least know chlorine is a
group 7 element)
Ionic compounds are held together by strong
electrostatic forces of attraction between
oppositely charged ions.
A structure formed as the result of all the
electrostatic forces between ions attracting each
other.
Sodium chloride
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2.1 Structure and bonding_3
Key Recall Question
1. What type of bonding is formed when atoms share
electrons?
2. How strong are covalent bonds?
3. Can you name seven small covalent molecules and
give their formula?
4. Can you name three macromolecules which have
giant covalent structures?
5. What are the boiling points of small covalent
molecules like and why?
6. Do simple covalent molecules conduct electricity
ad why/why not?
7. What is the structure of a metal like?
8. What is special about the electrons in a metal?
9. Name some reactive metals
10. Name some unreactive metals
Answer
Covalent
Very strong
Hydrogen (H2), Chlorine (Cl2), Oxygen (O2),
Hydrochloric acid (HCl), Water (H2O), Ammonia
(NH3) and Methane (CH4)
Diamond, graphite and silicon dioxide.
They have low melting and boiling points (so are
often gases) because the intermolecular forces
(forces between molecules, not within) are weak
so are easily broken
They do not conduct electricity because the
molecules do not have an overall electric charge.
Metals are giant structures of atoms arranged in a
regular pattern. They have positive metal ions with
electrons between the ions holding them together
with strong electrostatic attraction.
They are ‘delocalised’ so are free to move about
through the whole structure
Potassium, sodium, magnesium, etc.
Gold, platinum, silver
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C2.2 How structure influences properties_1
Key Recall Question
1. When a small covalent molecule like water boils,
what happens to it?
2. What is a giant ionic lattice?
3. What are the melting and boiling points of ionic
compounds (lattices) like and why?
4. Do most ionic compounds conduct electricity?
5. Which chemicals are diamond, graphite and silicon
dioxide made of?
6. What are the melting and boiling points of large
covalent molecules like diamond, graphite and silicon
dioxide like and why?
7. How are the atoms in diamond arranged and
which properties does this mean it has?
8. How are the atoms and electrons in graphite
arranged and which properties does this mean it has?
9. What are fullerenes?
10. What can fullerenes be used for?
Answer
The weak intermolecular forces are broken (forces
between the water molecules).
An ionic compound with a regular structure in
which there are strong electrostatic forces in all
directions between oppositely charged ions
They are high because the forces of attraction are
strong, and there are many of them, so a great deal
of energy is needed to break these bonds.
Only when dissolved or melted as this means the
charged ions are free to move and can therefore
carry a current
Diamond (Carbon), Graphite (Carbon) and sulicon
dioxide (Sulphur and Oxygen or ‘silica’)
They are very high because the covalent bonds
between atoms are very strong
One carbon atom is covalently bonded to four
other carbon atoms so diamond is very hard.
One carbon atom is covalently bonded to three
other carbon atoms to form layers. This means
there are delocalised electrons therefore the layers
are free to slide over each other because there are
no covalent bonds between them. This means
graphite is soft, slippery and able to conduct
electricity and heat (unlike diamond).
Fullerenes are hexagonal rings of carbon atoms.
They can be used for drug delivery into the body, in
lubricants, as catalysts, and in nanotubes for
reinforcing materials (e.g. tennis rackets)
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C2.2 How structure influences properties_2
Key Recall Question
Answer
1. In terms of their structure, why do metals conduct
heat and electricity?
2. What property do the layers in metals give them?
3. What are alloys?
Because they have delocalised electrons in their
structures.
They are able to be bent and shaped.
Metals which are usually made from two or more
different metals.
Because they have different sized atoms (due to
the two or more different type of metal) so the
layers are distorted and find it difficult to slide over
each other.
Nitinol (used in dental braces), shape memory
alloys can return to their original shape.
A substance made up from repeating monomers
What they are made from and the conditions
(temperatures, etc.) in which they were made.
They are produced using different catalysts and
reaction conditions.
Polymers which consist of individual, tangled
polymer chains. This means they do not have
strong intermolecular forces between the chains.
Polymers which consist of polymer chains with
cross links. This means that they have string forces
between chains so do not melt.
4. Why are alloys harder than pure metals?
5. Can you name a shape memory alloy and describe
what this term means?
6. What is a polymer?
7. What do the properties of polymers depend on?
8. What is the difference between how low density
(LD) and high density (HD) poly(ethane) are made?
9. What are thermosoftening polymers?
10. What are thermosetting polymers?
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C2.2 How structure influences properties_3
Key Recall Question
1. How big are nanoparticles?
2. What is the difference between nanoparticles and
substances made of the same elements but larger?
3. What sorts of new technologies could
nanoparticles be used to develop?
Answer
1-100nm (a few hundred atoms)
They have different properties and have a high
surface area to volume ratio.
New computers, new catalysts, new coatings,
highly selective sensors, stronger and lighter
construction materials and new cosmetics such as
sun tan creams and deodorants.
C2.3 Atomic structure, analysis and quantitative chemistry_1
Key Recall Question
4. What are the names of the three parts of an atom?
5. What can the ‘mass number’ of an element tell us?
6. What can the ‘atomic number’ of an element tell
us?
7. What is the relative mass and charge of a proton?
8. What is the relative mass and charge of a neutron?
9. What is the relative mass and charge of an
electron?
10. What is an isotope?
Answer
Proton, neutron and electron
The number of protons and neutrons
The number of protons
1 and +1
1 and 0
0 and -1
Atoms of the same element which have different
numbers of neutrons (e.g. Hydrogen always has 1
proton but can have 1, 2 or 3 neutrons)
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C2.3 Atomic structure, analysis and quantitative chemistry_2
Key Recall Question
Answer
1. Which isotope is the relative atomic mass of an
atom compared to?
2. What is the relative formula mass of a compound?
Carbon 12 (6 protons and 6 neutrons), 12 is the
average value for the isotopes of carbon.
It is the sum of the relative atomic masses of the
atoms shown in the formula.
1 mole of the substance (which contains 6.02 x 1023
atoms)
Add all the relative atomic masses of all the atoms
together; CO2; Carbon = 12 plus Oxygen = 16 plus
another Oxygen = 16 (because it is CO2 meaning 1
atom of carbon and 2 atoms of Oxygen) so the
relative formula mass is 12 + 16 + 16 = 44
Instrumental methods because they are accurate,
rapid and sensitive (think ARS) so can be used to
identify elements and compounds in very small
samples.
It can be used to identify additives in food.
3. What is the relative formula mass of a substance
when given in grams?
4. How do you calculate the relative formula mass of
carbon dioxide? (C = 12 and O = 16)
5. Which methods are used to detect elements and
compounds and why?
6. How is chemical analysis particularly useful in the
food industry?
7. Which technique is used to identify artificial
colours?
8. Which type of method is Gas chromatography
linked to mass spectroscopy (GC-MS) an example of?
9. What does GC-MS allow scientists to do?
Paper chromatography.
An instrumental method
Separate a mixture of compounds.
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C2.3 Atomic structure, analysis and quantitative chemistry_3
Key Recall Question
1. How is the substance to be analysed in GC-MS
carried through the equipment?
2. What is the substance to be analysed passed
through?
3. What happens to the substance as it passes
through the column?
Answer
Using a gas
The gas chromatography column packed with a
solid material.
Each element or compound within the substance
travels through the column at different speeds, so
the time taken can be used to help identify the
compound.
4. What is the gas chromatography column linked to? A mass spectrometer
5. What does the mass spectrometer show?
It will give different peaks which show how long
each substance was in the column for (retention
time). It will also give the relative molecular mass
of each of the compounds separated.
6. What is the name of the peak which shows the
The molecular ion peak
molecular mass?
7. If you want to calculate the percentage of a given
The relative mass of the element and the relative
element in a compound, which two pieces of
formula mass of the compound
information do you need?
8. What is the empirical formula?
The simplest ratio of elements in a compound
9. What information do you need to calculate the
The masses or percentages of elements in a
empirical formula?
compound.
10. Why is it not always possible to obtain the
1. the reaction may not go to completion because
calculated amount of a product when carrying out an it is reversible.
experiment?
2. some of the product is lost when separated
from the reaction mixture.
3. Some of the reactants may react in ways
different from the expected reaction
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C2.3 Atomic structure, analysis and quantitative chemistry_4
Key Recall Question
1. What is another name for the ‘amount’ of product
obtained in a chemical reaction?
2. What is ‘percentage yield’?
3. What is a reversible reaction?
4. Give an example of a reaction which is reversible
Answer
Yield
The amount of product obtained compared with
the maximum theoretical amount as a percentage
(amount of product obtained/theoretical amount x
100)
When the products of a reaction can react together
to produce the original reactants.
Ammonium chloride
ammonia + hydrogen
chloride.
Hydrated copper sulphate (blue) anhydrous
copper sulphate (white) + water
C2.4 Rates of reaction 1
Key Recall Question
5. Which two ways can you measure rates of
reaction?
6. Under what circumstances do chemical reactions
occur?
7. What is the ‘activation energy’ of a reaction?
8. What are the 5 ways to alter the rate of a reaction
Answer
1. Measuring the amount of reaction used in a
given amount of time (amount of reactant
used/time)
2. Measuring the amount of product formed in a
given amount of time (amount of product
formed/time)
When reacting particles collide with each other
with sufficient energy.
The minimum amount of energy particles must
have to react.
Temperature, concentration of reactants in a
solution, gas pressure, surface area of solid
reactants and presence of catalysts
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C2.4 Rates of reaction_2
Key Recall Question
1. Why does increasing temperature increase the
rate of reaction?
2. Why does increasing pressure of reacting gases
increase the rate of reaction?
3. Why does increasing the concentration of
reactants in solutions increase the rate of reaction?
4. Why does increasing the surface area of solid
reactants increase the rate of reaction?
5. How could you increase the surface area of a
marble (calcium carbonate) chip?
6. What is a catalyst?
7. Why are catalysts important in industry?
8. Can you give some examples of catalysts?
Answer
Because it increases the speed of the reacting
particles (they have more energy) so they collide
more frequently and more energetically.
Because it increases the frequency of collisions
(particles are closer together)
Because it increases the frequency of collisions
(more particles so more likely to collide).
Because it increases the frequency of collisions
(more particles on the surface available for
reactions)
You could grind it into a powder (if you added up
the surface area of each tiny part of the powder
this would be greater than surface area the original
chip)
It is a substance which changes the rate of
chemical reactions without being used up. Each
catalyst is specific to each reaction.
They increase the rate of reaction and therefore
can reduce costs.
Platinum (in the ignition of hydrogen or the
oxidation of ammonia). Manganese(IV) oxide or
enzymes in yeast/potato (in the decomposition of
hydrogen peroxide), etc.
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C2.5 Exothermic and endothermic reactions
Key Recall Question
1. What is an exothermic reaction?
2. Can you give three examples of exothermic
reactions?
3. Can you name some examples of everyday uses of
exothermic reactions?
4. What is an endothermic reaction?
5. Can you give an example of an endothermic
reaction?
6. Can you name some examples of everyday uses of
endothermic reactions?
7. If a reversible reaction is exothermic in one
direction will it be exothermic or endothermic in the
other direction?
8. Can you name an example of a reversible reaction
which is endothermic and exothermic?
9. What does soluble mean?
10. What does insoluble mean?
Answer
A reaction which transfers energy to the
surroundings (energy EXits)
Combustion reactions, many oxidation reactions
and neutralisation.
Self-heating cans (e.g. coffee) and hand warmers.
A reaction which takes in energy from the
surroundings (heat ENters)
Thermal decompositions
Sports injury packs.
Endothermic
Hydrated copper sulphate (blue) anhydrous
copper sulphate (white) + water
This is endothermic in this direction but the reverse
reaction is exothermic.
Dissolves in a solvent (typically water)
Does not dissolve in a solvent (typically water)
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C2.6 Acids, bases and salts_1
Key Recall Question
1. What are the four state symbols used in chemical
reactions?
2. What does aqueous mean?
3. What three substances can be used to react with
acids in order to make a soluble salt?
4. What is the difference between a base and an
alkali?
5. Why can you not use all metals when reacting
them with acid to make a soluble salt?
6. How do you make an insoluble salt using an acid
and a base?
7. What is used when an acid reacts with an alkali to
make a soluble salt in order to detect when the
reaction has happened to completion?
8. How can you get a solid salt from a salt solution?
9. Can you suggest how to make sodium chloride?
Answer
(s) solid, (l) liquid, (aq) aqueous and (g) gas.
Dissolved in water (a solution)
Metals, insoluble bases, alkalis
Bases are insoluble metal hydroxides or oxides and
alkalis are soluble hydroxides.
Some are too reactive (e.g. sodium) and some are
not reactive enough (e.g. gold)
Add the base to the acid until no more will react
then filter the excess (unreacted) solid off.
An indicator
Crystallise the solutions (allow the water to
evaporate leaving behind the salt)
React sodium hydroxide (alkali) with hydrochloric
acid (acid) to completion. Use universal indicator
to detect a neutral solution which will be green
colour. Add charcoal to remove the indicator then
filter this away. Crystallise the salt using an
evaporating dish and gentle heat.
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C2.6 Acids, bases and salts_2
Key Recall Question
1. How do you make an insoluble salt?
2. How can precipitation be used in industry?
3. What are bases?
4. What are alkalis?
5. In a reaction between an acid and a base or alkali,
what does the name of the alt produced depend on?
6. Which type of soluble salt does hydrochloric acid
produce when reacted with a base or alkali?
7. Which type of soluble salt does nitric acid produce
when reacted with a base or alkali?
8. Which type of soluble salt does sulphuric acid
produce when reacted with a base or alkali?
9. If sulphuric acid reacts with potassium hydroxide
what is the name of the soluble salt produced?
10. If zinc oxide reacts with nitric acid what is the
name of the soluble salt produced?
Answer
Mix appropriate amounts of solutions of ions so
that a precipitate is formed.
To remove unwanted ions from solutions, e.g. in
treating water or effluent.
Metal oxides and hydroxides which are insoluble.
Hydroxides which are soluble.
The metal in the base or alkali and the type of acid
used.
Chlorides.
Nitrates.
Sulphates.
Potassium sulphate.
Zinc nitrate
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C2.6 Acids, bases and salts_3
Key Recall Question
1. When ammonia dissolves in water does it produce
an acid or alkaline solution?
2. How is ammonia solution useful?
3. Which ion makes solutions acidic?
4. Which ion makes solutions alkaline?
5. What does the pH scale measure?
6. What is the range of the pH scale?
7. What is a neutral pH?
8. What is the pH of a strong acid?
9. What is the pH of a strong alkali?
10. What is a neutralisation reaction?
Answer
Alkaline
It is used to produce ammonium salts which are
useful as fertilisers
H+
OHHow acidic or alkaline a solution is (essentially how
many H+ or OH- ions are in the solution)
0-14
7
1 or 2
13 or 14
When and acid and alkali react so the H+ ions react
with the OH- ions to produce water.
H+(aq) + OH- (aq)  H2O(l)
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C2.7 Electrolysis
Key Recall Question
1. Why must an ionic substance be melted or
dissolved in water before electrolysis can be carried
out?
2. In order to carry out electrolysis on lead bromide
does it need to be dissolved or melted?
3. What happens when you pass an electric current
through molten lead bromide?
4. What is the term used for a substance that is
broken down by electrolysis?
5. What happens to the positive and negative ions
during electrolysis?
6. What happens to the positive ions at the negative
electrode?
7. What happens to the negative ions at the positive
electrode?
8. Does oxidation-reduction reactions always
involved oxygen?
9. If there is a mixture of ions in the electrolyte, what
will the products formed depend on?
10. How are reactions at electrodes represented?
Answer
Because when solid the ions are strongly attracted
to each other so cannot move. Dissolving or
melting the ionic substance means the ions are
free to move within the liquid or solution.
Melted
It gets broken down into its elements (lead and
bromine)
Electrolyte.
Positively charged ions move to the negative
electrode and negatively charged ions move to the
positive electrode.
The positive ions gain electrons (reduction)
The negative ions lose electrons (oxidation)
No, it is about the loss or gain of electrons.
Oxidation Is the Loss of electrons and Reduction Is
the Gain. (OILRIG)
The reactivity of the elements involved. The least
reactive will be most likely to gain or lose electrons
at the electrodes.
By half equations e.g. 2Cl-  Cl2 + 2eor 2Cl- - 2e-  Cl2 (where e- represents an
electron)
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C2.7 Electrolysis_2
Key Recall Question
1. What is electroplating?
2. How is electrolysis used to manufacture
aluminium?
3. Why is cryolite required in the electrolysis to
produce aluminium?
4. In the electrolysis of aluminium oxide, what is
formed at the negative electrode?
5. In the electrolysis of aluminium oxide, what is
formed at the positive electrode?
6. Which element are electrodes typically made
from?
7. If oxygen is formed at an electrode, what usually
happens?
8. What are the products of the electrolysis of
sodium chloride solution?
9. How are the products of the electrolysis of sodium
chloride solution use in industry?
Answer
Where electrolysis is used to plate objects for a
variety of reasons e.g. copper plating or silver
plating (cutlery, etc.)
Using a molten (melted) mixture of aluminium
oxide and a substance called cryolite.
It lowers the melting point of aluminium oxide.
Aluminium
Oxygen
Carbon
The oxygen reacts with the carbon in the electrode
to form carbon dioxide and the electrode will need
to be regularly replaced.
Hydrogen and chlorine (at electrodes). Sodium
hydroxide solution is also produced.
Sodium hydroxide is important for the production
of soap and chlorine for the production of bleach
and plastics.
2Cl- - 2e-  Cl2
10. Can you write the half equation for the oxidation
reaction at the positive electrode in the electrolysis of
sodium chloride solution?
11. Can you write the half equation for the reduction 2H+ + 2e-  H2
reaction at the negative electrode in the electrolysis
of sodium chloride solution?
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