Physics 5054 · O Level · Thermal properties and temperature

Thermal properties and temperature — practice question

Water evaporating from the skin’s surface leads to cooling. If a refrigerator is turned on, the cooling coils at the top of the inside space become cold. A convection current is then produced, which cools the air inside the refrigerator.
(a(i))[2]

Describe, with reference to particles, how evaporation leads to cooling.

(a(ii))[1]

State one difference between evaporation and boiling.

(b(i))[2]

Explain how the cooling coils produce a convection current in the air inside the refrigerator.

(b(ii))[2]

The food in the refrigerator starts at $20.0\,^\circ\text{C}$. It has a mass of $3.6\,\text{kg}$ and a specific heat capacity of $3000\,\text{J}\,(\text{kg}\,^\circ\text{C})^{-1}$. Calculate the final temperature of the food after $160\,000\,\text{J}$ of thermal energy is taken away from it.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: The faster particles escape (from water or skin)

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