Science 9 · Unit 8: Rates of reaction · Cambridge Lower Secondary Science Stage 9

Questions

1. 1. How does increasing the concentration of acid affect the rate of reaction?

   • It increases the rate.
   • It decreases the rate.
   • It has no effect.
   Check

2. 2. Why does a higher concentration make a reaction faster?

   • The acid is hotter.
   • There are more acid particles in the same volume, so collisions are more frequent.
   • The particles move faster.
   • The particles are bigger.
   Check

3. 3. What is a catalyst?

   • a substance that slows a reaction
   • a substance that speeds up a reaction and is unchanged at the end
   • a reactant that is used up
   • a product of the reaction
   Check

4. 4. How can Zara and Sofia make five different concentrations from one bottle of acid?

   • Use different pieces of zinc.
   • Pour the acid into five beakers without measuring.
   • Mix measured volumes of acid and water, keeping the total volume the same.
   • Heat the acid to different temperatures.
   Check

5. 5. Which equipment measures the volumes of acid and water accurately?

   • a beaker
   • a measuring cylinder
   • a test tube
   • a spatula
   Check

6. 6. What do the girls measure when they carry out the reaction?

   • the colour of the zinc
   • the volume of hydrogen made over time, or the time for the zinc to react
   • the mass of the beaker only
   • the temperature of the room
   Check

7. 📖 This question is about a text that students read in the app.

   7. Why was the ×0 concentration not used?

   • It is too strong.
   • It is just water, so there is no acid to react.
   • It has too much acid.
   • It is too hot.
   Check

8. 📖 This question is about a text that students read in the app.

   8. To make the ×4 concentration, how much water does Arun add to 40 cm³ of acid?

   • 40 cm³
   • 4 cm³
   • 10 cm³
   • 50 cm³
   Check

9. 📖 This question is about a text that students read in the app.

   9. To make the ×2 concentration, how much water does Arun add to 20 cm³ of acid?

   • 20 cm³
   • 50 cm³
   • 30 cm³
   • 10 cm³
   Check

10. 10. Arun's graph shows results for ×4, ×3 and ×2 concentrations, but the lines aren't labelled. Which concentration is line P, the steepest?

    • ×2
    • ×1
    • ×4
    • ×3
    Check

11. 11. Where would the line for the ×5 concentration be on Arun's graph?

    • below the ×2 line
    • the same as the ×3 line
    • steeper than ×4, levelling off sooner
    • a flat line at 0
    Check

12. 12. Marcus and Zara must collect 100 cm³ of carbon dioxide as fast as possible. Which variable are they NOT allowed to change?

    • the temperature
    • the size of the marble chips
    • the mass of marble and the volume and type of acid
    • the equipment for collecting gas
    Check

13. 13. Which two changes would collect the gas fastest?

    • use smaller marble chips and warm the acid
    • use bigger marble chips and cool the acid
    • add water to the acid
    • use less acid
    Check

14. 14. Which equipment measures a volume of gas accurately?

    • a thermometer
    • a beaker
    • a gas syringe
    • a test tube
    Check

15. 15. Which practical difficulty could make the gas collection slower than it should be?

    • The gas syringe is too accurate.
    • The marble chips are too small.
    • The acid is too warm.
    • Gas escapes before the bung is fitted, or the syringe sticks.
    Check