AQA GCSE Chemistry –
Paper 2 2026 |
Comprehensive Revision
Guide, Practice Questions,
Answers & Exam Prep |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
,What is the rate of a chemical reaction? How fast the reactants are changed into products
Examples of slow chemical reactions Rusting of iron
Chemical weathering e.g. acid rain
Example of moderate chemical reactions Reaction of magnesium with an acid to produce a gentle stream of bubbles
Examples of fast chemical reactions Burning
Explosions - over in a fraction of a second
Rate of Reaction Graphs Steeper lines = faster rate - the quickest reactions have the steepest lines &
become flat in the least time
Shallower lines = slower rate - the slowest reactions have the shallowest lines &
become flat in the most time
What is collision theory? It affects the rate of a chemical reaction
1) The collision frequency of reacting particles - the more collisions there are, the
faster the reaction is
2) The energy transferred during a collision - particles have to collide with enough
energy for the collision to be successful
What does the rate of reaction depend on? 1) Temperature
2) Concentration of a solution or the pressure of gas
3) Surface area - this changes depending on the size of the lumps of a solid
4) The presence of a catalyst
Rate of Reaction - Increasing the Temperature 1) Causes the particles to move faster - if they're moving faster, they're going to
collide more frequently
2) The faster the particles move, the more energy they have, so more of the
collisions will have enough energy to make the reaction happen
Rate of Reaction - Increasing the Concentration/Pressure 1) A more concentrated solution will contain more particles in the same volume of
water
2) If the pressure of a gas is increased, there will be more particles occupying a
smaller space
3) This causes collisions between the reactant particles to be more frequent
Rate of Reaction - Increasing the Surface Area Breaking a solid up into smaller pieces will increase its surface area to volume ratio
- for the same volume of the solid, the particles around it will have more area to
work on, thus there will be more frequent collisions
Rate of Reaction - Using a Catalyst Not part of the overall reaction equation - doesn't get used up in the reaction itself
They all decrease the activation energy needed for the reaction to occur - they do
this by providing an alternative reaction pathway with a lower activation energy
Equation for Rate of Reaction Rate of reaction = Amount of reactant used or amount of product formed / Time
Measuring the Rate of Reaction - Precipitation & Colour 1) Recording visual changes in a reaction if the initial solution is transparent and the
Change product is a precipitate which clouds the solution
2) Observing a mark through the solution & measure how long it takes for it to
disappear - the faster it disappears, the faster the rate of reaction
3) If the reactants are coloured & the products are colourless, time how long it takes
for the solution to lose (or gain) its colour
4) Results can be subjective & you can't plot a rate of reaction graph from the
results
, Measuring the Rate of Reaction - Change in Mass 1) Measuring the speed of a reaction that produces a gas can be carried out using a
mass balance
2) As the gas is released, the mass disappearing is quickly measured on the
balance - the quicker the reading on the balance drops, the faster the reaction
3) Measurements can be taken at regular intervals for a rate of reaction graph to
easily find the rate
4) Most accurate but the gas is released straight into the room
Measuring the Rate of Reaction - The Volume of Gas 1) Uses a gas syringe to measure the volume of gas given off
Given Off 2) The more gas given off during a given time interval, the faster the reaction
3) Gas syringes usually give volumes accurate to the nearest cm³, so they're quite
accurate
4) Measurements can be taken at regular intervals for a rate of reaction graph to be
plotted
5) If the reaction is too vigorous, the plunger could easily be blown out of the end of
the syringe
How do you find the mean rate for the whole reaction? Work out the overall change in the y-value (amount of product formed or amount of
reactant used) and divide it by the total time taken for the reaction
How do you find the rate of reaction at a particular point? Finding the gradient of the curve at that point - do this by drawing a tangent to the
curve and work out the gradient of the tangent
Reversible reactions 1) As the reactants react, their concentrations fall, so the forward reaction will slow
down - but, as more and more products are made and their concentrations rise, the
backward reaction will speed up
2) After a while the forward reaction will be going at exactly the same rate as the
backward one - the system is at equilibrium
What happens at equilibrium during a reversible reaction? Both reactions are still happening, but there's no overall effect - the concentrations
of reactants & products have reached a balance & won't change
When will the reaction reach equilibrium? When the reaction takes place in a closed system - none of the reactants or
products can escape & nothing else can get in
What happens if the equilibrium lies to the left? The concentration of reactants is greater than that of the products
What happens if the equilibrium lies to the right? The concentration of products is greater than that of the reactants
What does the position of equilibrium depend on? 1) The temperature
2) The pressure (only affects the equilibria involving gases)
3) The concentration of the reactants & products
Are reversible reactions endothermic or exothermic? They can be both - if the reaction is endothermic in one direction, it will be
exothermic in the other
The energy transferred from the surroundings by the endothermic reaction is equal
to the energy transferred to the surroundings during the exothermic reaction
Le Chatelier's Principle The idea that if you change the conditions of a reversible reaction at equilibrium, the
system will try to counteract that change
It's used to predict the effect of any changes you make to a reaction system
Paper 2 2026 |
Comprehensive Revision
Guide, Practice Questions,
Answers & Exam Prep |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
,What is the rate of a chemical reaction? How fast the reactants are changed into products
Examples of slow chemical reactions Rusting of iron
Chemical weathering e.g. acid rain
Example of moderate chemical reactions Reaction of magnesium with an acid to produce a gentle stream of bubbles
Examples of fast chemical reactions Burning
Explosions - over in a fraction of a second
Rate of Reaction Graphs Steeper lines = faster rate - the quickest reactions have the steepest lines &
become flat in the least time
Shallower lines = slower rate - the slowest reactions have the shallowest lines &
become flat in the most time
What is collision theory? It affects the rate of a chemical reaction
1) The collision frequency of reacting particles - the more collisions there are, the
faster the reaction is
2) The energy transferred during a collision - particles have to collide with enough
energy for the collision to be successful
What does the rate of reaction depend on? 1) Temperature
2) Concentration of a solution or the pressure of gas
3) Surface area - this changes depending on the size of the lumps of a solid
4) The presence of a catalyst
Rate of Reaction - Increasing the Temperature 1) Causes the particles to move faster - if they're moving faster, they're going to
collide more frequently
2) The faster the particles move, the more energy they have, so more of the
collisions will have enough energy to make the reaction happen
Rate of Reaction - Increasing the Concentration/Pressure 1) A more concentrated solution will contain more particles in the same volume of
water
2) If the pressure of a gas is increased, there will be more particles occupying a
smaller space
3) This causes collisions between the reactant particles to be more frequent
Rate of Reaction - Increasing the Surface Area Breaking a solid up into smaller pieces will increase its surface area to volume ratio
- for the same volume of the solid, the particles around it will have more area to
work on, thus there will be more frequent collisions
Rate of Reaction - Using a Catalyst Not part of the overall reaction equation - doesn't get used up in the reaction itself
They all decrease the activation energy needed for the reaction to occur - they do
this by providing an alternative reaction pathway with a lower activation energy
Equation for Rate of Reaction Rate of reaction = Amount of reactant used or amount of product formed / Time
Measuring the Rate of Reaction - Precipitation & Colour 1) Recording visual changes in a reaction if the initial solution is transparent and the
Change product is a precipitate which clouds the solution
2) Observing a mark through the solution & measure how long it takes for it to
disappear - the faster it disappears, the faster the rate of reaction
3) If the reactants are coloured & the products are colourless, time how long it takes
for the solution to lose (or gain) its colour
4) Results can be subjective & you can't plot a rate of reaction graph from the
results
, Measuring the Rate of Reaction - Change in Mass 1) Measuring the speed of a reaction that produces a gas can be carried out using a
mass balance
2) As the gas is released, the mass disappearing is quickly measured on the
balance - the quicker the reading on the balance drops, the faster the reaction
3) Measurements can be taken at regular intervals for a rate of reaction graph to
easily find the rate
4) Most accurate but the gas is released straight into the room
Measuring the Rate of Reaction - The Volume of Gas 1) Uses a gas syringe to measure the volume of gas given off
Given Off 2) The more gas given off during a given time interval, the faster the reaction
3) Gas syringes usually give volumes accurate to the nearest cm³, so they're quite
accurate
4) Measurements can be taken at regular intervals for a rate of reaction graph to be
plotted
5) If the reaction is too vigorous, the plunger could easily be blown out of the end of
the syringe
How do you find the mean rate for the whole reaction? Work out the overall change in the y-value (amount of product formed or amount of
reactant used) and divide it by the total time taken for the reaction
How do you find the rate of reaction at a particular point? Finding the gradient of the curve at that point - do this by drawing a tangent to the
curve and work out the gradient of the tangent
Reversible reactions 1) As the reactants react, their concentrations fall, so the forward reaction will slow
down - but, as more and more products are made and their concentrations rise, the
backward reaction will speed up
2) After a while the forward reaction will be going at exactly the same rate as the
backward one - the system is at equilibrium
What happens at equilibrium during a reversible reaction? Both reactions are still happening, but there's no overall effect - the concentrations
of reactants & products have reached a balance & won't change
When will the reaction reach equilibrium? When the reaction takes place in a closed system - none of the reactants or
products can escape & nothing else can get in
What happens if the equilibrium lies to the left? The concentration of reactants is greater than that of the products
What happens if the equilibrium lies to the right? The concentration of products is greater than that of the reactants
What does the position of equilibrium depend on? 1) The temperature
2) The pressure (only affects the equilibria involving gases)
3) The concentration of the reactants & products
Are reversible reactions endothermic or exothermic? They can be both - if the reaction is endothermic in one direction, it will be
exothermic in the other
The energy transferred from the surroundings by the endothermic reaction is equal
to the energy transferred to the surroundings during the exothermic reaction
Le Chatelier's Principle The idea that if you change the conditions of a reversible reaction at equilibrium, the
system will try to counteract that change
It's used to predict the effect of any changes you make to a reaction system
