What happens to gases when they are heated?

When gases are heated, they gain energy, which increases the velocity of the gas molecules. As the temperature rises, the molecules move more rapidly, causing them to spread out and occupy a greater volume. This phenomenon is described by the gas laws, particularly Charles's Law, which states that the volume of a gas is directly proportional to its temperature when pressure is held constant.

As the gas expands, it creates less density compared to its cooler state. Understanding this behavior is critical for various applications, including thermodynamics and engineering, where gas behavior plays a significant role in processes such as combustion, temperature control, and the design of engines and HVAC systems.

The other options reflect misunderstandings about gas behavior under heat. Gases do not contract when heated; rather, they expand due to increased kinetic energy. They do not remain the same; heating significantly alters their physical state and behavior. Lastly, gases do not become liquid simply from heating; instead, they require cooling and increased pressure to transition into a liquid state.