Question

Which of the following situations would cause the greatest increase in the motion of molecules in a system?   A. The system absorbs 75 J of heat, and its volume is halved.   B. The system releases 75 J of heat, and its volume doubles.   C. The system absorbs 75 J of heat, and its volume doubles.   D. The system releases 75 J of heat, and its volume is halved.

Answer 1

The correct answer is A. The system absorbs 75 J of heat, and its volume is halved.

Step-by-step explanation:

For this question, we want the system's molecular motion to experience an INCREASE. So if your question is asking for a DECREASE in molecular motion, this answer does not apply! Instead, it would be "The system releases 75 J of heat, and its volume doubles." Let me explain.

Molecular motion increases with increasing temperature, since collisions increase. For that reason, we want to look for the answer choice that experiences an increase in temperature, with would mean that the system absorbs (NOT RELEASES) 75 J of heat. Additionally, a system's molecular motion increases when its volume decreases. With a smaller volume, molecules are closer together and hit each other more often, increasing molecular motion. And so, for the motion of molecules to INCREASE, the volume would actually have to decrease or be halved! Answer choice A is correct!

If that explanation isn't enough to sway you, know that I took this computer-scored test and received 100%. If you review your study notes from this unit, you'll see that my answer makes sense. I hope that helped! :)

Answer 2

The answer is B. When the system absorbs energy, the molecules gain more kinetic energy and hence start to move faster. Doubling the size of the system also gives more room for the molecules to move randomly around the system before colliding with other molecules hence increasing their motion.