A Level Chemistry A
Topic Exploration Pack

Boltzmann Distribution Curves
Learner Questions

T
1
E a

Tasks
1. Label the x and y axes
2. If you calculated the area under the graph, what would this number be a measure of?
3. What does the shaded area under the graph represent?
4. What does the line labelled E a represent?

Tasks
5. The graph you have drawn represents the distribution of energies of molecules in a sample of gases. On your diagram, sketch a second distribution curve, for the same gas, but at a lower temperature, label this T
2
.
6. What has happened to the proportion of molecules above line E a
? How would this affect the rate of a reaction?

Tasks
7. Are the areas under the two curves equal? Explain your answer.
8. Now sketch another curve, on the same axes, for the same sample of gases at a higher temperature, label this T
3
.
9. What has happened to the area beyond the line E a
?

Tasks
10. Other than by changing the temperature, how else could you increase the area beyond the line E a
?

T
2
T
1
Answers
T
2
E a

Answers
1. See graph on previous slide.
2. Total number of particles present.
3. Number of particles with an energy higher than the activation energy.
4. Activation energy.
5. See previous slide.

Answers
6. Fewer molecules with an energy above the activation energy, so fewer collisions will lead to a reaction.
7. Yes, the area under the two curves are equal because the sample of gases is the same.
8. See Slide 9.

Answers
9. The area has increased, so there are now more molecules with an energy above the activation energy.
10. A catalyst could be added, which would lower the activation energy, hence increasing the number of molecules with an energy above the activation energy.

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