Topic 2.1: Thermal Energy Transfers Questions

0.080 kg of steam at 100 °C is passed into a cold container, where it all condenses to water still at 100 °C.

The specific latent heat of vaporisation of water is 2.3 × 10⁶ J kg⁻¹.

Calculate the thermal energy released as the steam condenses.

Warm air above a heater rises and circulates around a room.

Identify which method of thermal energy transfer this describes, and identify what physically moves to carry the energy.

Two blocks, P and Q, have the same mass.

They are each given the same amount of thermal energy.

Block P ends up hotter than block Q.

Identify which block has the larger specific heat capacity, and explain your choice.

State what is meant by the specific heat capacity of a substance.

A liquid metal has a density of 7.0 × 10³ kg m⁻³.

A sample of the liquid has a mass of 0.42 kg.

Determine the volume of the sample.

Calculate the thermal energy needed to raise the temperature of 1.5 kg of copper from 18 degrees C to 68 degrees C.

The specific heat capacity of copper is 3.8 × 10² J kg⁻¹ K⁻¹.

State what is meant by the specific latent heat of vaporisation of a substance.

State the one method of thermal energy transfer that can carry energy across a vacuum, and state what physically travels in that process.

A sealed cylinder contains a real gas.

Identify what makes up the internal energy of this gas.

State the two contributions that together make up the internal energy of a substance.

A 1500 W immersion heater is switched on for 3.0 minutes inside a tank holding 2.0 kg of oil.

The oil's temperature rises from 15 degrees C to 45 degrees C.

Assuming all the electrical energy heats the oil, determine the specific heat capacity of the oil.

A solar water heater is to warm 120 kg of water from 16 degrees C to 52 degrees C over one afternoon.

The specific heat capacity of water is 4200 J kg⁻¹ K⁻¹.

Estimate the total thermal energy that must be delivered to the water.

A solid brick wall of area 10 m² and thickness 0.25 m separates a workshop at 22 °C from the outside air at 4 °C.

The thermal conductivity of the brick is k = 0.72 W m⁻¹ K⁻¹.

Show that the rate of thermal energy conducted through the wall is about 500 W.

A student claims that supplying 9.6 × 10³ J of energy to a 0.30 kg sample of a metal will raise its temperature by about 80 K.

The metal's specific heat capacity is 4.0 × 10² J kg⁻¹ K⁻¹.

Show that the student's claim is correct.

A double-glazed window has two glass panes, each of area 1.5 m² and thickness 4.0 × 10⁻³ m, with k = 0.80 W m⁻¹ K⁻¹ for the glass.

Consider just one pane with its inside surface at 19 °C and outside surface at 7 °C.

Calculate the rate of thermal energy conducted through that pane, state its unit, and explain why making the pane thicker would reduce this rate.

An electric kettle transfers 1.68 × 10⁵ J of thermal energy to 0.50 kg of water, with negligible heat loss.

The water starts at 20 degrees C and has a specific heat capacity of 4200 J kg⁻¹ K⁻¹.

Calculate the final temperature of the water, and state one assumption you have made.

A frozen pond loses heat by conduction up through its ice to the cold air above.

Explain how the rate of heat conduction changes as the ice layer grows thicker, assuming the temperatures above and below the ice stay the same.

A solid cube of side 0.050 m has a mass of 1.1 kg.

Calculate the density of the material and state whether it would sink or float in water (density 1.0 × 10³ kg m⁻³).

A 0.80 kg metal block is heated by a 50 W heater for 2.0 minutes (so it receives 6.0 × 10³ J).

Its temperature rises from 22 degrees C to 47 degrees C.

Calculate the specific heat capacity of the metal, and explain why the value you obtain is likely to be an overestimate.

A block of solid candle wax has a mass of 0.36 kg and a volume of 4.0 × 10⁻⁴ m³.

When the wax is fully melted, the same mass occupies 4.5 × 10⁻⁴ m³.

Calculate the density of the wax in each state, and explain, using the particle model, why the solid is the denser state.