International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which of the following best describes the movement of gas particles?

1. They vibrate around fixed points

2. They do not move at all

3. They move quickly and freely

4. They move at a slow pace

The correct answer is: They move quickly and freely

The movement of gas particles is best described by their ability to move quickly and freely. In a gas, particles are in constant motion, bouncing off one another and the walls of their container. This high kinetic energy allows them to overcome any attractive forces between them, leading to a state in which they can spread out and fill the entire volume of their container. This behavior is a key characteristic of gases and explains why they can be compressed and expand to fill available space. Other descriptions, such as particles vibrating around fixed points or not moving at all, apply to solids or liquids rather than gases, and the notion of moving at a slow pace contradicts the typical properties observed in gaseous states. Thus, the correct answer accurately reflects the dynamic and energetic nature of gas particles.