Question

question 4 of 30
the temperature of 500 ml of water is 16⁰c. what happens to the water when thermal energy is transferred to it?

a. the volume of the water increases because thermal energy increases as volume increases.

b. the temperature of the water increases because the average kinetic energy of the water molecules increases.

c. the temperature of the water decreases because the average kinetic energy of the water molecules decreases.

d. the volume of the water decreases because thermal energy decreases as volume decreases.

Explanation:

• Option A: Thermal energy transfer to water (not at phase change temp here) mainly affects molecular kinetic energy, not volume increase due to that reasoning (volume change from heating is due to expansion, but the cause - effect in A is wrong as thermal energy increase doesn't directly cause volume increase in that stated way).
• Option B: When thermal energy is added to water (not at boiling or freezing), the average kinetic energy of water molecules increases. Temperature is a measure of average kinetic energy, so temperature increases. This matches the concept of heat transfer and molecular motion.
• Option C: Adding thermal energy should increase, not decrease, molecular kinetic energy and thus temperature, so C is incorrect.
• Option D: Adding thermal energy would not decrease volume; in fact, water (above 4°C) expands when heated, and the reasoning about thermal energy decreasing with volume is wrong.

Answer:

B. The temperature of the water increases because the average kinetic energy of the water molecules increases.