AQA GCSE Chemistry - Paper 2 Exam |
Questions And Answers
|100%Guaranteed Pass| Latest Exam
2026-2027 |Graded A+
Measurements for quantity of product or reactant -ANSWER Either as mass in g or as
volume in cm³
Measurements for the rate of reaction -ANSWER Either as g/s, cm³/s, or mol/s
Factors which affect rate of chemical reaction -ANSWER - *Temperature*: a faster
temperature means faster reaction
- *Concentration / pressure*: a higher concentration or pressure means a faster reaction
- *Surface area*: a larger surface area: volume ratio means a faster reaction
- *Catalysts*: a reaction in the presence of a catalyst is faster
Collision theory -ANSWER This states that a chemical reaction can only happen when
reacting particles collide with each other with enough energy.
Activation energy -ANSWER This is the minimum energy required for a reaction to take
place.
How surface area, concentration or pressure changes rate of reaction in terms of
collision theory -ANSWER This increases the frequency of collisions, as there are more
particles that are able to collide, increasing rate of reaction.
How temperature changes rate of reaction in terms of collision theory -ANSWER This
increases the frequency of collisions as well as the energy the collisions have,
increasing rate of reaction.
Catalysts -ANSWER - A catalyst is a substance that changes the rate of reaction
- It is not used up during the reaction, and therefore does not show up in the products or
reactants
- Different reactions require different catalysts, for example an enzyme
- The catalyst does this by supplying a different pathway to the reaction that requires a
lower activation energy, shown in the picture
Reversible reactions -ANSWER This is a reaction in which the products can react to
produce the original reactants
A+B⇌C+D
,Example of a reversible reaction -ANSWER This reaction is reversible, meaning the
reactants can be heated to get the products as well as the products can be cooled to
get the reactants:
Ammonium chloride ⇌ ammonia + hydrogen chloride
Energy changes in reversible reactions -ANSWER If a reaction is endothermic in one
direction, it is exothermic in the other. The same amount of energy is transferred each
way.
Equilibrium in a reversible reaction -ANSWER If the apparatus are set up to prevent the
escape of reactants or products, an equilibrium can be reached, in which the rate of
forward and reverse reactions are the same. This will always occur in consistent
conditions.
The effect of changing concentration in a reversible reaction -ANSWER When the
concentration of one product or reactant is changed, the system is no longer at
equilibrium:
- If the concentration of the reactants is increased, more products are formed until a
balance is reached
- If the concentration of the products is increased, more reactants will form until a
balance is reached
The effect of increasing temperature in a reversible reaction -ANSWER When the
temperature is *increased*:
- More product is formed for an endothermic reaction
- Less product is formed for an exothermic reaction
The effect of decreasing temperature in a reversible reaction -ANSWER When the
temperature is *decreased*:
- Less product is formed for an endothermic reaction
- More product is formed for an exothermic reaction
The effect of changing pressure in a reversible reaction -ANSWER For a gaseous
reaction at equilibrium:
- An increase in pressure causes the equilibrium position to shift towards the side of the
smaller number of moles, meaning whichever side has less moles, more of it will be
formed
- A decrease in pressure causes the equilibrium position to shift towards the side with
more moles, meaning whichever side has more moles, more of it will be formed
Hydrocarbon -ANSWER A hydrocarbon is a material that contains only carbon and
hydrogen atoms.
Alkanes -ANSWER - These are saturated, meaning there are only single bonds between
atoms
, - They are relatively unreactive, although they do combust
- Their single bonds are quite strong
- They are a homologous series of hydrocarbons (organic compounds with the same
functional group and similar chemical properties)
- There are trends in their physical properties
Formula for alkanes -ANSWER Cn H2n+2
The first four alkanes -ANSWER - Methane
- Ethane
- Propane
- Butane
Formula for methane -ANSWER CH₄
Formula for ethane -ANSWER C₂H₆
Formula for propane -ANSWER C₃H₈
Formula for butane -ANSWER C₄H₁₀
Crude oil -ANSWER - A finite resource found in rocks
- Mostly ancient biomass, e.g. plankton, which has been buried in mud
- It is a mixture of many compounds, mostly hydrocarbons, which are mostly alkanes
- They are separated by fractional distillation
Why fractional distillation works -ANSWER The hydrocarbons in crude oil can be
separated into fractions, which are chemicals that have a similar boiling point. These
are molecules with a similar number of carbon atoms. Each fraction has different
properties and uses, a lot of which are processed to produce fuels and feedstock for the
petrochemical industry, e.g. petrol, kerosene, heavy fuel oil and liquefied petroleum
gases.
Process of fractional distillation -ANSWER 1. Oil is firstly heated so it turns into a gas and
evaporates
2. It is piped to the bottom of the column
3. The gas rises up the column and it gradually cools
4. Different compounds in the mixture have different condensation points, so they turn
back into a liquid at different places in the column
Properties of molecules at the top of the column -ANSWER - Small
- Low boiling point
- Very volatile (easily evaporated)
Questions And Answers
|100%Guaranteed Pass| Latest Exam
2026-2027 |Graded A+
Measurements for quantity of product or reactant -ANSWER Either as mass in g or as
volume in cm³
Measurements for the rate of reaction -ANSWER Either as g/s, cm³/s, or mol/s
Factors which affect rate of chemical reaction -ANSWER - *Temperature*: a faster
temperature means faster reaction
- *Concentration / pressure*: a higher concentration or pressure means a faster reaction
- *Surface area*: a larger surface area: volume ratio means a faster reaction
- *Catalysts*: a reaction in the presence of a catalyst is faster
Collision theory -ANSWER This states that a chemical reaction can only happen when
reacting particles collide with each other with enough energy.
Activation energy -ANSWER This is the minimum energy required for a reaction to take
place.
How surface area, concentration or pressure changes rate of reaction in terms of
collision theory -ANSWER This increases the frequency of collisions, as there are more
particles that are able to collide, increasing rate of reaction.
How temperature changes rate of reaction in terms of collision theory -ANSWER This
increases the frequency of collisions as well as the energy the collisions have,
increasing rate of reaction.
Catalysts -ANSWER - A catalyst is a substance that changes the rate of reaction
- It is not used up during the reaction, and therefore does not show up in the products or
reactants
- Different reactions require different catalysts, for example an enzyme
- The catalyst does this by supplying a different pathway to the reaction that requires a
lower activation energy, shown in the picture
Reversible reactions -ANSWER This is a reaction in which the products can react to
produce the original reactants
A+B⇌C+D
,Example of a reversible reaction -ANSWER This reaction is reversible, meaning the
reactants can be heated to get the products as well as the products can be cooled to
get the reactants:
Ammonium chloride ⇌ ammonia + hydrogen chloride
Energy changes in reversible reactions -ANSWER If a reaction is endothermic in one
direction, it is exothermic in the other. The same amount of energy is transferred each
way.
Equilibrium in a reversible reaction -ANSWER If the apparatus are set up to prevent the
escape of reactants or products, an equilibrium can be reached, in which the rate of
forward and reverse reactions are the same. This will always occur in consistent
conditions.
The effect of changing concentration in a reversible reaction -ANSWER When the
concentration of one product or reactant is changed, the system is no longer at
equilibrium:
- If the concentration of the reactants is increased, more products are formed until a
balance is reached
- If the concentration of the products is increased, more reactants will form until a
balance is reached
The effect of increasing temperature in a reversible reaction -ANSWER When the
temperature is *increased*:
- More product is formed for an endothermic reaction
- Less product is formed for an exothermic reaction
The effect of decreasing temperature in a reversible reaction -ANSWER When the
temperature is *decreased*:
- Less product is formed for an endothermic reaction
- More product is formed for an exothermic reaction
The effect of changing pressure in a reversible reaction -ANSWER For a gaseous
reaction at equilibrium:
- An increase in pressure causes the equilibrium position to shift towards the side of the
smaller number of moles, meaning whichever side has less moles, more of it will be
formed
- A decrease in pressure causes the equilibrium position to shift towards the side with
more moles, meaning whichever side has more moles, more of it will be formed
Hydrocarbon -ANSWER A hydrocarbon is a material that contains only carbon and
hydrogen atoms.
Alkanes -ANSWER - These are saturated, meaning there are only single bonds between
atoms
, - They are relatively unreactive, although they do combust
- Their single bonds are quite strong
- They are a homologous series of hydrocarbons (organic compounds with the same
functional group and similar chemical properties)
- There are trends in their physical properties
Formula for alkanes -ANSWER Cn H2n+2
The first four alkanes -ANSWER - Methane
- Ethane
- Propane
- Butane
Formula for methane -ANSWER CH₄
Formula for ethane -ANSWER C₂H₆
Formula for propane -ANSWER C₃H₈
Formula for butane -ANSWER C₄H₁₀
Crude oil -ANSWER - A finite resource found in rocks
- Mostly ancient biomass, e.g. plankton, which has been buried in mud
- It is a mixture of many compounds, mostly hydrocarbons, which are mostly alkanes
- They are separated by fractional distillation
Why fractional distillation works -ANSWER The hydrocarbons in crude oil can be
separated into fractions, which are chemicals that have a similar boiling point. These
are molecules with a similar number of carbon atoms. Each fraction has different
properties and uses, a lot of which are processed to produce fuels and feedstock for the
petrochemical industry, e.g. petrol, kerosene, heavy fuel oil and liquefied petroleum
gases.
Process of fractional distillation -ANSWER 1. Oil is firstly heated so it turns into a gas and
evaporates
2. It is piped to the bottom of the column
3. The gas rises up the column and it gradually cools
4. Different compounds in the mixture have different condensation points, so they turn
back into a liquid at different places in the column
Properties of molecules at the top of the column -ANSWER - Small
- Low boiling point
- Very volatile (easily evaporated)
