A chemical reaction where the reactants form products that, in turn, react together to reform the reactants.

A salt that contains water molecules within its crystal structure, shown by a dot in its formula, e.g. hydrated copper(II) sulfate (CuSO₄·5H₂O).

A salt that does not contain any water molecules in the crystal structure, e.g. anhydrous copper(II) sulfate (CuSO₄).

Used to show that a chemical reaction is reversible.

Used to show the direction of an (irreversible) chemical reaction, showing that reactants form products.

Introduction to reversible chemical reactions

Combined science

In the Rates and energy changes unit, pupils learned about how energy changes are always involved in reaction, along with a range of methods for measuring and comparing rates of reaction using properties of reactants and/or products.

This unit covers corrosion, prevention methods, and properties of alloys, ceramics, polymers, and metals. It explores industrial processes like the Haber process, fertiliser production, reaction rates, yields, atom economy, and the trade-offs involving conditions and equilibrium.

Industrial chemistry

Physical activity and equipment requiring safe use

reactants form products, and the reaction goes to completion

both forward and backward reactions occur under the correct conditions

Match the following key terms to their definition.

Which of the following symbols is used to indicate a reversible reaction?

In reversible reactions, the forward and backward reactions have different energy changes.
When energy is taken in from the surroundings, the reaction is called an {{}} reaction.

True or false? In a reversible reaction, the forward reaction needs to reach completion before the backward reaction can start. 

The direction of reversible reactions can be influenced by changing conditions, such as temperature. By cooling a reaction down, the system will change to favour the {{}} reaction.

contains water molecules in its crystal structure (dot in the formula)

does not contain any water molecules in the crystal structure

Match the following key words to their definition.

energy is transferred from the surroundings to the reaction

energy is transferred from the reaction to the surroundings

all atomic bonds are broken before new ones are made

particles must collide with enough energy to react

Which of the following statements about chemical reactions are correct?

The rate of a chemical reaction is equal to the amount of product formed per unit {{}}.

A chemical reaction produces 0.5 g of gas in 10 seconds.
Which is the correct rate of reaction?

The rate of a reaction can be changed by varying concentration or temperature, but also by changing the {{}} of a solid reactant.

a catalyst speeds up a reaction without being used up or chemically changed

catalysts are specific; different reactions require different catalysts

enzymes are biological catalysts that speed up reactions in living cells

reactions need catalysts to start and only take place when a catalyst is present

Which of the following statements about catalysts is incorrect?

Content guidance

Risk assessment required - equipment

Adult supervision required

This lesson will be removed by end of Summer Term 2025.

Introduction to reversible chemical reactions

Lesson outcome

Content guidance

This lesson will be removed by end of Summer Term 2025.