iStarSign inScience 9 · Unit 8: Rates of reaction · Cambridge Lower Secondary Science Stage 9
8.3 Temperature and the rate of reaction
15 questions · e.g. Why does heating speed up a reaction?
Questions
1. Sodium thiosulfate solution reacts with hydrochloric acid. Why does the mixture become cloudy?
- Sulfur is produced, which is insoluble and forms a precipitate.
- The acid freezes.
- Carbon dioxide bubbles are made.
- Salt crystals form on the surface.
2. In the sodium thiosulfate investigation, what is a trial run?
- the final experiment whose results you use
- a race to see who finishes first
- a practice experiment to check you can do the experiment safely and effectively
- an experiment with no reactants
3. Why must the room be well ventilated during the sodium thiosulfate experiment?
- The solution gets very hot.
- Hydrogen gas could explode.
- The reaction uses up all the oxygen.
- Sulfur dioxide gas is produced.
- It is less at 40 °C.
- It is more at 40 °C.
- None is made at 40 °C.
- It is the same, but it is made faster at 40 °C.
5. For reactant particles to react, what must happen?
- They must collide with enough energy.
- They must touch gently.
- They must stay still.
- They must change state.
6. Why is the rate of reaction high at the start?
- The products speed it up.
- The particles are cold.
- There are few particles.
- There are lots of reactant particles, so collisions are frequent.
7. Why does the rate of reaction slow down after a time?
- The particles get faster.
- The reactants are being used up, so there are fewer collisions.
- The temperature rises.
- More reactants are made.
8. Why does increasing the temperature increase the rate of reaction?
- Particles move faster, so they collide more often and with more energy.
- There are more particles.
- The particles get bigger.
- The particles stop moving.
9. Which metal and acid are suitable for timing a reaction at different temperatures?
- potassium and concentrated sulfuric acid
- magnesium ribbon and dilute hydrochloric acid
- copper and dilute hydrochloric acid
- gold and water
10. Which safety precaution should Sofia and Marcus take?
- Use concentrated acid.
- Wear eye protection and heat the acid gently in a water bath.
- Hold the flask with bare hands.
- Boil the acid strongly.
11. Which variables must they keep the same?
Check12. How will they know when the reaction has stopped?
- The thermometer reads 100 °C.
- The acid turns blue.
- No more bubbles are made, and the metal has gone.
- The stopwatch runs out.
13. What happens to the time for the reaction as the temperature increases?
Check- a straight line going up
- a curve that slopes downwards, falling steeply at first then less steeply
- a flat line
- a curve that goes up steeply
- There would be no reaction.
- The times would be the same.
- The times would all be shorter.
- The times would all be longer.