Question

question 28 of 30
what must happen for ice to melt at a given pressure?

a. the orderliness of the water molecules must decrease.

b. thermal energy must be transferred from the ice to its surroundings.

c. thermal energy must be transferred to the ice from its surroundings.

d. the average kinetic energy of the water molecules must decrease.

Explanation:

• Option A: When ice melts, water molecules become more disordered (from a crystalline structure to a liquid with more random motion), but the key for melting is energy input, not just about orderliness change as the main requirement. So A is not the main factor for the melting process at a given pressure.
• Option B: If thermal energy is transferred from ice to surroundings, ice would get colder or freeze more, not melt. So B is incorrect.
• Option C: Melting is a phase change from solid to liquid, which requires energy (heat) to break the intermolecular forces. So thermal energy must be transferred to ice from surroundings (like heat absorption) for it to melt at a given pressure. This is correct.
• Option D: Average kinetic energy of molecules is related to temperature. If average kinetic energy decreases, temperature decreases, which would not cause melting (melting requires energy input to increase molecular motion enough to break the solid structure). So D is incorrect.

Answer:

C. Thermal energy must be transferred to the ice from its surroundings.