Question

what do these two changes have in common?
dew appearing on grass in the morning
ice crystals forming on a window
select all that apply.
both are chemical changes.
both are caused by heating.
both conserve mass.
both are only physical changes.

Explanation:

1. Analyze the two changes: Dew forming (condensation, gas to liquid) and ice crystals forming (deposition or freezing, gas to solid or liquid to solid) are both physical changes (no new substance formed).
2. Check "Both are chemical changes": Incorrect, as no chemical reaction occurs.
3. Check "Both are caused by heating": Incorrect, these changes occur due to cooling (temperature drop causes water vapor to condense or freeze).
4. Check "Both conserve mass": Correct, according to the law of conservation of mass, mass is conserved in physical (and chemical) changes.
5. Check "Both are only physical changes": Correct, as both involve changes in state (phase) without altering the chemical identity of water.

Answer:

• Both conserve mass.
• Both are only physical changes.