An exothermic chemical reaction is a type of reaction in which energy is transferred from the reactants to the surroundings, e.g. combustion.

An endothermic chemical reaction is a type of reaction in which energy is transferred from the surroundings to the products, e.g. photosynthesis.

The minimum energy that the particles must have in order to react is known as the activation energy.

A reaction profile is a diagram showing the energy changes during exothermic and endothermic reactions.

Reaction profiles

Combined science

In the Rate of Reaction unit, pupils will build on their understanding of energy changes to learn about the factors that influence the rate of chemical reactions.

In the Fuels and Energetics unit, pupils learned about energy changes during chemical reactions, including exothermic and endothermic reactions.

Energy changes in reactions

energy changes during a chemical reaction

Which of the following reaction profiles shows an endothermic reaction?

Which of the following reaction profiles correctly represents the activation energy of the reaction with a red arrow, and where R is the reactant and P is the product?

The energy of the products is higher than the reactants.

The energy of the products is lower than the reactants.

How can you identify an exothermic reaction from its reaction profile?

Activation energy does not affect the reaction rate.

Higher activation energy means a faster reaction rate.

Higher activation energy means a slower reaction rate.

How does the activation energy of a reaction influence its rate?

It can occur at lower temperatures, saving energy costs.

Why might a reaction with a low activation energy be preferred in industrial processes?

It has no effect on the activation energy.

It increases the activation energy required for the reaction to start.

It lowers the activation energy required for the reaction to start.

What is the role of a catalyst in a chemical reaction?

Energy is transferred from the reactants to the surroundings.

Energy is transferred from the surroundings to the reactants.

What happens during an exothermic reaction?

 What happens during an endothermic reaction?

{{}} is needed for a chemical reaction to start.

the disappearance of energy during a reaction

the movement of energy from one store to another

What is energy transfer in a chemical reaction?

the minimum energy needed for the reaction to start 

What is the role of activation energy in a chemical reaction?

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