Which of the following phase changes involves the absorption of heat?

• A. Melting (solid to liquid)
• B. Freezing (liquid to solid)
• C. Condensation (gas to liquid)
• D. Deposition (gas to solid)

Answer: (A)

Verified step by step guidance

1. Understand that phase changes can be either endothermic (absorbing heat) or exothermic (releasing heat).
2. Recall that melting (solid to liquid) requires energy input to overcome the forces holding the solid together, so it absorbs heat.
3. Recognize that freezing (liquid to solid) releases heat because the molecules lose energy as they form a solid structure.
4. Know that condensation (gas to liquid) releases heat as gas molecules lose energy to become liquid.
5. Understand that deposition (gas to solid) also releases heat because gas molecules lose energy directly to form a solid.