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

What is the energy level of particles in a gas?

1. Low energy

2. Moderate energy

3. High energy

4. Variable energy

The correct answer is: High energy

In a gas, the particles possess high energy compared to the particles in solids and liquids. This is because gas particles are in constant motion, moving freely and rapidly throughout the space available to them. The kinetic energy of gas particles is significantly greater, which allows them to overcome intermolecular forces that might otherwise keep them closer together, as seen in liquids and solids. This high energy state results in the ability of gas particles to expand to fill the entire volume of their container, leading to characteristics such as low density and compressibility. Additionally, as temperature increases, the energy of gas particles also increases, further affirming their high energy state. Other options may suggest lower energy levels, but they do not accurately describe the nature of gas behavior, where the freedom of movement and kinetic activity are paramount.