Which of the following best describes how adding or removing heat from a system can affect its state of matter?

• A. Adding heat always turns a substance directly into a gas, regardless of its initial state.
• B. The state of matter is unaffected by changes in heat; only pressure can change the state.
• C. Adding heat can cause a solid to melt into a liquid, while removing heat can cause a liquid to freeze into a solid.
• D. Removing heat from a gas will always turn it into a liquid, never a solid.

Answer: (C)

Verified step by step guidance

1. Understand that the state of matter (solid, liquid, gas) depends primarily on temperature and pressure conditions.
2. Recognize that adding heat to a substance increases its internal energy, which can cause phase changes such as melting (solid to liquid) or vaporization (liquid to gas), depending on the initial state and conditions.
3. Know that removing heat decreases the internal energy, which can cause phase changes such as freezing (liquid to solid) or condensation (gas to liquid).
4. Realize that phase changes occur at specific temperatures called melting points and boiling points, and these transitions do not happen instantaneously or always directly from solid to gas without passing through the liquid phase (except in special cases like sublimation).
5. Conclude that the correct description is that adding heat can cause a solid to melt into a liquid, and removing heat can cause a liquid to freeze into a solid, reflecting the typical behavior of substances under normal conditions.