Identify the arrows that show removal of thermal energy when matter changes state.
The Correct Answer and Explanation is:
Correct Answer:
The arrows that show removal of thermal energy when matter changes state are the ones pointing from:
- Gas → Liquid (Condensation)
- Liquid → Solid (Freezing)
- Gas → Solid (Deposition)
Explanation:
When matter changes from one state to another, thermal energy—also known as heat—must either be added or removed. Changes in the state of matter occur due to changes in the energy of the particles that make up the substance. The removal of thermal energy causes particles to slow down and move closer together, resulting in phase changes from a higher-energy state to a lower-energy one.
Condensation occurs when a substance changes from a gas to a liquid. In this process, thermal energy is removed from the gas, causing its particles to lose energy. As a result, the particles move more slowly and begin to stick together to form a liquid. For example, water vapor condenses into liquid water on a cold surface.
Freezing is the process where a liquid becomes a solid. When thermal energy is removed from a liquid, its particles slow down further and arrange themselves into fixed, orderly positions, forming a solid. This happens, for instance, when water freezes into ice in a freezer.
Deposition is a less commonly observed change in which a gas transforms directly into a solid without passing through the liquid state. This occurs when thermal energy is removed rapidly from a gas. An everyday example is frost forming on a window when water vapor in the air deposits as solid ice crystals.
These changes—condensation, freezing, and deposition—all indicate that thermal energy is leaving the system. The removal of heat reduces the kinetic energy of the particles, which leads to a more ordered and compact state of matter. This principle is foundational in understanding energy transfer and phase changes in physical science.
