B.1 Thermal energy transfers: Practice Questions

Which of the following is the correct SI unit for specific heat capacity?

A sample of a pure substance is heated at a constant rate from its solid state. The graph shows the variation of its temperature with time. Which feature of the graph is used to determine the specific latent heat of fusion of the substance?

A block of ice with mass \( 0.10\text{ kg} \) at \( 0^\circ\text{C} \) is added to \( 0.20\text{ kg} \) of liquid water at \( 20^\circ\text{C} \) in an insulated container.
Specific latent heat of fusion of ice = \( 3.3 \times 10^5\text{ J kg}^{-1} \)
Specific heat capacity of water = \( 4200\text{ J kg}^{-1}\text{ K}^{-1} \)
What is the final temperature and state of the mixture at thermal equilibrium?

Two solid blocks, X and Y, are in thermal contact. Block X is at a temperature of \( 350\text{ K} \) and block Y is at a temperature of \( 300\text{ K} \). What describes the net flow of thermal energy between the blocks?

An ideal blackbody at an absolute temperature \( T \) radiates a total power \( P \). If the absolute temperature of the blackbody is doubled to \( 2T \), what will be the new power radiated?

(a) Distinguish between specific heat capacity and specific latent heat.
(b) An electric heater of power 1500 W is used to heat 2.0 kg of a liquid in a container of negligible heat capacity. The temperature of the liquid increases from 20°C to 80°C in 180 seconds. Calculate the specific heat capacity of the liquid.
(c) In reality, the calculated value is higher than the actual value. Suggest two reasons why this might be the case.

A 0.45 kg copper calorimeter contains 0.80 kg of water at 20°C. A 0.25 kg piece of ice at -15°C is added to the water.

(a) Calculate the energy required to raise the temperature of the ice to 0°C.
(b) Determine whether all the ice melts. Support your answer with calculations.
(Specific heat capacity of copper = \( 390 \, \text{J kg}^{-1}\text{K}^{-1} \), water = \( 4180 \, \text{J kg}^{-1}\text{K}^{-1} \), ice = \( 2100 \, \text{J kg}^{-1}\text{K}^{-1} \). Specific latent heat of fusion of ice = \( 3.34 \times 10^5 \, \text{J kg}^{-1} \)).