Science 7 · Unit 8: Changes to materials · Cambridge Lower Secondary Science Stage 7

Questions

1. 1. What is neutralisation?

   • the substances made in a reaction
   • a solid formed when two liquids react
   • a reaction where an acid is cancelled out by an alkali
   • a substance that eats away other materials
   Check

2. 2. What is a precipitate?

   • a solid formed when two liquids react
   • a gas given off in a reaction
   • a liquid that is an acid
   • rain
   Check

3. 3. What does the pH scale show?

   • the strength of an acid or an alkali
   • the volume of a liquid
   • the mass of a solid
   • the temperature of a liquid
   Check

4. 4. What does "corrosive" mean?

   • a solid formed in a reaction
   • having a pH of 7
   • catches fire easily
   • able to dissolve or eat away other materials
   Check

5. 5. What are reactants?

   • the substances you start with in a reaction
   • the substances made in a reaction
   • the solid formed when two liquids react
   • the equipment used
   Check

6. 6. What are products?

   • the substances made in a chemical reaction
   • the indicator colours
   • the substances you start with
   • the equipment used
   Check

7. 7. What pH does an acid have?

   • less than 7
   • exactly 7
   • more than 7
   Check

8. 8. What pH does an alkali have?

   • less than 7
   • exactly 7
   • more than 7
   Check

9. 9. Vinegar and baking powder fizz when mixed. What sign of a reaction is this?

   • The colour changes.
   • A precipitate forms.
   • It gets cold.
   • A gas is given off.
   Check

10. 10. Which of these is another sign that a chemical reaction has happened?

    • dissolving
    • a colour change
    • a change of shape
    • melting
    Check

11. 11. Mixing two solutions makes the beaker feel warm. What does this show?

    • Nothing has happened.
    • A reaction has taken place.
    • The beaker is broken.
    • One of the solutions is frozen.
    Check

12. 12. Two clear liquids are mixed and the mixture goes cloudy as a solid forms. What sign of a reaction is this?

    • Nothing has reacted.
    • A precipitate forms.
    • A gas is given off.
    • The temperature drops.
    Check

13. 13. How do you test for oxygen?

    • It relights a glowing splint.
    • A lighted splint gives a squeaky pop.
    • It turns limewater milky.
    • It turns universal indicator green.
    Check

14. 14. How do you test for carbon dioxide?

    • It turns blue litmus green.
    • It relights a glowing splint.
    • It gives a squeaky pop.
    • It turns limewater milky.
    Check

15. 15. Four tubes contain air, oxygen, hydrogen and carbon dioxide. A lighted splint gives a squeaky pop in one. Which gas is it?

    • air
    • carbon dioxide
    • hydrogen
    • oxygen
    Check

16. 16. A glowing splint relights in one of the tubes. Which gas is it?

    • carbon dioxide
    • oxygen
    • hydrogen
    • air
    Check

17. 17. You have found the hydrogen and the oxygen. How can you tell the air from the carbon dioxide?

    • Use a lighted splint on both.
    • Smell them both.
    • Bubble each through limewater. Carbon dioxide turns it milky.
    • Look at their colours.
    Check