Chemistry Paper 2 - Topics - Revision Organiser - Chapter 8 - Rates and equilibrium

Sep 5, 2026

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Revision organiser content for Chemistry Paper 2 focusing on Chapter 8: Rates and equilibrium. It explains collision theory and activation energy, then outlines practical factors that increase reaction rate: temperature, concentration, gas pressure, and surface area of solids. The organiser also covers catalysts and reaction conditions in a closed system, applying Le Châtelier’s principle to predict shifts at equilibrium. It concludes with reversible reactions and how dynamic equilibrium is reached, including key definitions for exam preparation.

LanguageEnglish

CategoryExam

FormatPDF

Pages12

Reading Time30 min

AccessFree to download

Chapter 8: Rates and equilibrium

Knowledge organiser 1

Collision theory - Factors affecting rate of reaction

Catalysts

Knowledge organiser 2

Reaction conditions - Le Châtelier’s principle

Changing concentrations - Changing pressure - Changing temperature

Reversible reactions

How dynamic equilibrium is reached

Equilibrium

CHEMISTRY PAPER 2 TOPICS REVISION ORGANISER Chapter 8: Rates and equilibrium 1 Knowledge organiser For a reaction to occur, the reactant particles need to collide. When the particles collide, they need to have enough energy to react or they will just bounce apart. This amount of energy is called the activation energy. You can increase the rate of a reaction by: • increasing the frequency of collisions • increasing the energy of the particles when they collide. Collision theory Factors affecting rate of reaction | Condition that increases rate | How is this condition caused? | Why it has that effect | | --- | --- | --- | | increasing the temperature | Heat the container in which thereaction is taking place. | 1 particles move faster, leading to more frequent collisions
2 particles have more energy, so more collisions result in a reaction
note that these are two separate effects | | increasing the concentration of solutions | Use a solution with more solute in the same volume of solvent. | there are more reactant particles in thereaction mixture, so collisions become more frequent | | increasing the pressure of gases | Increase the number of gas particles you have in the container or make the container smaller. | less space between particles means more frequent collisions | | increasing the surface area of solids | Cut the solid into smaller pieces, or grind it to create a powder, increasing the surface area. Larger pieces decrease
the surface area. | only reactant particles on the surface of a solid are able to collide and react; the greater the surface area the more reactant particles are exposed, leading to more frequent collisions | Catalysts Some reactions have specific substances called catalysts that can be added to increase the rate. These substances are not used up in the reaction. A catalyst provides a different reaction pathway that has a lower activation energy. As such, more particles will collide with enough energy to react, so more collisions result in areaction. energy Chapter 8: Rates and equilibrium 2 Knowledge organiser The conditions of a reaction refer to the external environment of the reaction. When the reaction occurs in a closed system, you can change the conditions by: • changing the concentration of one of the substances • changing the temperature of the entire reaction vessel • changing the pressure inside the vessel. Le Châtelier’s principle (HT only) Reaction conditions At equilibrium, the amount of reactants and products is constant. In order to change the amounts of reactant and product at equilibrium the conditions of the reaction must be changed. The closed system will then counteract the change by favouring either the forward reaction or thereverse reaction. This is known as Le Châtelier’s principle. For example, lowering the concentration of the product in the system causes the forward reaction to be favoured to increase the concentration of the product. Changing concentrations (HT only) | Change | Effect | Explanation | | --- | --- | --- | | increase the pressure | favours the reaction that results in fewer molecules | decreasing the number of molecules within the vessel opposes the change because it decrease pressure | | decrease the pressure | favours the direction that results in more molecules | increasing the number of molecules within the vessel opposes the change because it increase pressure | | Change | Effect | Explanation | | --- | --- | --- | | decrease concentration of product | favours the forward reaction | opposes the change by making less reactant and more product | | increase concentration of product | favours the reverse reaction | opposes the change by making more reactant and less product | | decrease concentration of reactant | favours the reverse reaction | opposes the change by making more reactant and less product | | increase concentration of reactant | favours the forward reaction | opposes the change by maki

FAQs

How does collision theory explain reaction rate?

For a reaction to occur, reactant particles must collide with enough energy to react. If collisions lack sufficient energy, particles only bounce apart.

What factors can increase the rate of a reaction?

Rate can be increased by raising collision frequency and collision energy. This is achieved by increasing temperature, concentration of solutions, pressure of gases, and the surface area of solids.

How does Le Châtelier’s principle predict changes at equilibrium?

When reaction conditions in a closed system are changed, the system counters the change by favouring the forward or reverse reaction. For example, lowering product concentration favours the forward reaction to restore product amounts.

Sep 5, 2026

Upload by Eliana