OCR GCSE Combined Science
Topic questions The rate and extent of chemical change Collision theory and activation energy
8 questions · 57 marks · about 1 hour
Why do reactions happen faster at higher temperatures?
A The activation energy increases.
B The particles are closer together.
C The particles collide with more energy.
D The size of the particles increases.
15* A student investigates the rate of reaction between pieces of marble chips and an excess of dilute hydrochloric acid.
The diagram shows the equipment they use.
The student measures the total volume of carbon dioxide gas produced every minute until the reaction finishes.
They do two different experiments and plot a graph of the results.
Which experiment has the greater rate of reaction?
Explain your answer by including:
• information from the graph
• a description of how the experiments might be different
• ideas about the reacting particle model including particles and their collisions.
The student has difficulty filling the measuring cylinder with water.
They change the measuring cylinder for a different piece of apparatus which allows them to measure the volume of hydrogen more accurately.
Name the piece of apparatus they use and complete the diagram below to show this apparatus.
Name of piece of apparatus........
Complete the balanced symbol equation for the reaction.
The student repeats the experiment. The only difference is they use a higher concentration of acid.
Draw a line on the graph to show the results of this experiment.
If the experiment is repeated at a higher temperature, the rate of reaction increases.
Explain why. Use ideas about particles and collisions.
The student has difficulty filling the measuring cylinder with water.
They change the measuring cylinder for a different piece of apparatus which allows them to measure the volume of hydrogen more accurately.
Name the piece of apparatus they use and complete the diagram below to show this apparatus.
Name of piece of apparatus........
Complete the balanced symbol equation for the reaction.
The student repeats the experiment. The only difference is they use a higher concentration of acid.
Draw a line on the graph to show the results of this experiment.
If the experiment is repeated at a higher temperature, the rate of reaction increases.
Explain why. Use ideas about particles and collisions.
The gradient of the tangent gives the rate of reaction. Use the tangent to calculate the rate of reaction at the start of the reaction.
Give your answer to 1 decimal place.
Rate of reaction =........ cm3 / minute
What happens to the rate of reaction as the reaction progresses?
Explain your answer using ideas about particles and collisions.
Another student repeats the experiment.
They increase the concentration of the dilute hydrochloric acid. They keep everything else in the experiment the same.
Does the gradient of the graph at the start of this student’s reaction decrease, increase or stay the same compared to the first student’s experiment?
Tick (✓) one box.
Give a reason for your answer.
Write down the volume of hydrogen gas that is produced at the end of this reaction.
The gradient of the tangent gives the rate of reaction. Use the tangent to calculate the rate of reaction at the start of the reaction.
Give your answer to 1 decimal place.
Rate of reaction =........ cm3 / minute
What happens to the rate of reaction as the reaction progresses?
Explain your answer using ideas about particles and collisions.
Another student repeats the experiment.
They increase the concentration of the dilute hydrochloric acid. They keep everything else in the experiment the same.
Does the gradient of the graph at the start of this student’s reaction decrease, increase or stay the same compared to the first student’s experiment?
Tick (✓) one box.
Give a reason for your answer.
Write down the volume of hydrogen gas that is produced at the end of this reaction.
Look at the reaction.
Which statement explains why the rate of reaction changes as the pressure increases?
A The energy of the particles increases.
B The particles collide with more force.
C The particles move faster.
D There are more particles in the same volume.
A student adds some magnesium to dilute hydrochloric acid (HC l).
Magnesium chloride (MgCl2) and hydrogen gas is formed.
Write a balanced symbol equation for this reaction.
Identify the independent variable in the investigation.
Identify two control variables in the investigation.
The results at 0.75 mol / dm3 are repeated. (d)
This is a graph of the student’s results.
Concentration of acid (mol / dm3)
What conclusion can you make from these results?
Include ideas about particles in your answer.
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Combined Science starter pack