The speed of the particles decreases. The particles begin to move in a straight line. The particles begin to move with a greater force. The motion of the particles becomes more random.
I gave my students this multiple choice question: The freezing point of nitrous oxide is -91°C. Which of the following statements best describes the effect on the particles in liquid nitrous oxide as its temperature is lowered to -91°C?

Only one answer is correct among these 4 choices:
- The speed of the particles decreases.
- The particles begin to move in a straight line.
- The particles begin to move with a greater force.
- The motion of the particles becomes more random.

Could you tell me which one is correct?

The speed of the particles decreases.