Difficulty: Hard

Average Score: 33%

In which phase change is energy being released to the surroundings?

Rationale

Rain turning into ice when it hits a cold surface.

This phase change, known as freezing, occurs when water molecules lose energy and transition from a liquid state to a solid state, thereby releasing energy in the form of heat to the surrounding environment.

A (Water in sweat becoming a gas as the sweat dries) YOUR ANSWER

This process, known as evaporation, requires energy input from the surroundings, specifically heat, to allow liquid water molecules to gain enough energy to transition into vapor. As a result, energy is absorbed rather than released during this phase change.

B (A solid iron bar becoming liquid as it is heated) YOUR ANSWER

This phase change is called melting, which involves the solid iron absorbing heat energy from its environment to overcome intermolecular forces and transition into a liquid state. Consequently, energy is taken in during this process, rather than being released.

C (Rubbing alcohol turning into gas when it is applied to a warm surface) YOUR ANSWER

Similar to evaporation, this process involves the absorption of heat energy from the warm surface to facilitate the transition of rubbing alcohol from liquid to gas. Therefore, energy is absorbed, not released, in this phase change.

D (Rain turning into ice when it hits a cold surface) CORRECT

During this phase change, water molecules lose heat energy as they transition from a liquid to a solid state, resulting in energy being released into the surroundings. This process is an example of freezing and is characterized by the release of latent heat.

Conclusion

In summary, phase changes can either absorb or release energy depending on the direction of molecular movement. The transition of rain into ice when it contacts a cold surface exemplifies a scenario where energy is released to the surroundings, marking it as a freezing process. The other options illustrate phase changes that absorb energy, highlighting the unique attributes of freezing in energy dynamics.

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