Lesson T4.3.1

T4.3.1 What catalysts do Quiz: KS3 Chemistry, Unit 4

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T4.3.1, What catalysts do: 20 multiple choice questions for the KS3 Chemistry (National Curriculum), Unit 4: Chemical reactions, written with Revision Ninja.

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The 20 questions

  1. What is a catalyst?

    • A substance that becomes a product of the reaction
    • A substance that is used up to make the products
    • A substance that slows a reaction by stopping collisions
    • A substance that speeds up a reaction without being used up

  2. Which statement about catalysts is correct?

    • They always stop the reaction completely
    • They become the main product of the reaction
    • They are used up at the end of the reaction
    • They are not changed at the end of the reaction

  3. How does a catalyst increase the rate of a reaction?

    • It raises the temperature of the reactants
    • It gives an alternative route that needs less energy
    • It adds more reactant particles to the mixture
    • It increases the mass of the reactants

  4. What is the effect of a catalyst on the amount of product made?

    • It reduces the amount of product made to zero
    • It doubles the amount of product made
    • It does not change the amount of product made
    • It changes the product into a different substance

  5. Why is a catalyst useful in industry?

    • It makes reactions faster and cheaper, because less energy and time are needed
    • It converts all the reactants into useful energy that can be sold back to the factory
    • It removes the need for any reactants by making the product from water alone
    • It makes the product heavier and easier to sell to customers in the market

  6. Which metal is used as a catalyst in a car's catalytic converter?

    • Calcium chloride
    • Sodium
    • Carbon dioxide
    • Platinum

  7. Which substance is a common catalyst for breaking down hydrogen peroxide into water and oxygen?

    • Manganese(IV) oxide
    • Calcium carbonate
    • Sodium chloride
    • Magnesium ribbon

  8. Why does a catalyst not appear in the overall equation?

    • Because it is used and regenerated, so there is no overall change to it
    • Because it has no atoms in it, so it cannot appear in any equation at all
    • Because it is always a gas that escapes from the flask during the reaction
    • Because it is destroyed as the reaction starts and so is no longer present

  9. Which factor, besides a catalyst, speeds up a reaction?

    • Decreasing the concentration of reactants
    • Making the solid reactant into large lumps
    • Lowering the surface area of a solid reactant
    • Increasing the temperature of the reactants

  10. A student adds a little manganese dioxide to hydrogen peroxide and oxygen bubbles out faster. What does the manganese dioxide do?

    • It acts as a catalyst, speeding up the reaction without being used up
    • It changes the hydrogen peroxide into a solid that settles to the bottom
    • It reacts with the hydrogen peroxide to make water and oxygen as products
    • It stops the reaction by absorbing the oxygen that would otherwise form

  11. Why do enzymes in the body act as catalysts?

    • They act as food for the cell
    • They speed up reactions in living things without being used up
    • They stop reactions in living cells by absorbing products
    • They are destroyed by every reaction they speed up

  12. What happens to the catalyst at the end of the reaction?

    • It has become the product of the reaction and is removed from the flask
    • It is still there, unchanged in mass and chemical identity
    • It has dissolved completely and cannot be recovered from the mixture afterwards
    • It has been converted into energy that is released as heat to the surroundings

  13. Two identical reactions are run, and the one with a catalyst makes the same mass of product in half the time. What does this show?

    • The catalyst slowed the reaction to half speed by blocking the reactants from meeting
    • The catalyst increased the rate of the reaction without changing the product mass
    • The catalyst used up half of the reactants, so only half the product was formed
    • The catalyst increased the mass of product made in the same reaction time

  14. Why is a catalyst reused many times in a reaction?

    • It is absorbed into the product and returns later
    • It breaks into smaller parts that are reused
    • It is not used up, so it can take part again
    • It stays inactive once it has reacted once

  15. What is the key difference between a catalyst and a reactant?

    • A reactant appears unchanged in the products, while a catalyst is used up
    • A reactant speeds up the reaction, while a catalyst slows it
    • A reactant is used up in the reaction, while a catalyst is not
    • A reactant is always a gas, while a catalyst is always a solid

  16. Why might a catalyst be described as lowering the energy needed for a reaction to start?

    • It adds energy to the reactants so that they start moving and react faster
    • It makes the reactants lighter so that they need less energy to start reacting
    • It provides a different pathway that needs less energy for the reactants to react
    • It removes energy from the products so that they can form more quickly

  17. A catalyst is added to a reaction in a closed flask. Which statement about the total mass of the flask is correct?

    • The total mass depends on the colour of the catalyst that is used in the reaction
    • The total mass drops because the catalyst is destroyed and lost as the reaction proceeds
    • The total mass increases by the full mass of the catalyst that was added to the flask
    • The total mass is unchanged, because the catalyst is not used up and the mass of atoms is conserved

  18. Why should a catalyst be checked for purity before it is used in a reaction?

    • Impurities can slow or stop the catalyst from working properly
    • Impurities are needed for the catalyst to dissolve
    • Impurities turn the catalyst into a product
    • Impurities always make the catalyst heavier

  19. Which of these is NOT a feature of catalysts?

    • They are used up in the reaction and must be replaced
    • They do not appear in the overall balanced equation
    • They speed up reactions without being changed
    • They can be reused many times

  20. Why does a catalyst that works well at one temperature not always work at another?

    • Catalysts only work when the temperature is held at exactly zero degrees Celsius
    • Catalysts always work equally well at every temperature in the reaction vessel
    • Catalysts become solid at all temperatures, so they cannot work in any reaction
    • Catalysts can be damaged or change their effectiveness at extreme temperatures

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