Which of the following changes can occur in a substance as the energy of its particles decreases?

• A. A gas condenses into a liquid.
• B. A solid melts into a liquid.
• C. A liquid evaporates into a gas.
• D. A solid sublimes into a gas.

Answer: (A)

Verified step by step guidance

1. Understand that when the energy of particles in a substance decreases, the particles lose kinetic energy and move less vigorously.
2. Recall the phase changes and their relation to energy: melting and evaporation require energy input (particles gain energy), while condensation and freezing involve energy release (particles lose energy).
3. Analyze each option: 'A gas condenses into a liquid' involves particles losing energy and coming closer together, which matches the scenario of decreasing particle energy.
4. 'A solid melts into a liquid', 'A liquid evaporates into a gas', and 'A solid sublimes into a gas' all require an increase in particle energy, so they do not occur when energy decreases.
5. Conclude that the correct change when particle energy decreases is the gas condensing into a liquid.