The kinetic energy of a sample of gas in a container of fixed volume is represented by the distribution curve shown in Graph 1 below - VCE - SSCE Chemistry - Question 20 - 2018 - Paper 1

To analyze the differences between Graph 1 and Graph 2, we can observe the shape and position of the kinetic energy distribution.

1. Understanding Graphs: The area under these graphs represents the number of particles at different energy levels. An increase in the number of particles at lower energy levels in Graph 2 suggests a decrease in average kinetic energy.

2. Choosing the Correct Statement:

   • Option A asserts that the average kinetic energy of gas molecules has decreased, which is consistent with the observed change in the shape of the distribution curve. This indicates that fewer particles have high energy, supporting the idea that the average energy has dropped.
   • Other options, such as adding gas or increasing temperature, would typically result in a shift towards higher energy particles or broader distributions rather than a decrease in average energy.

Therefore, the correct answer is A.