Topic 2.1: Thermal Energy Transfers Questions

A sealed cylinder contains a real gas.

Identify what makes up the internal energy of this gas.

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

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.

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.

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

State the two contributions that together make up the internal energy 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.

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.

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.

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.

A student records the density of a fixed sample of water as it is warmed from 0 °C and finds it rises to a maximum near 4 °C before falling again.

Identify the temperature of maximum density, and discuss how this anomaly helps fish survive in a pond during a freezing winter.

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 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 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 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.

A 0.50 kg sample of a liquid is heated by an immersion heater that supplies energy at a constant rate.

The liquid's temperature first rises by 40 K, which takes 100 s.

The liquid then boils at constant temperature, and 0.020 kg of it vaporizes during the next 50 s.

Assuming all the supplied energy goes to the liquid, what is the ratio of the specific heat capacity c to the specific latent heat of vaporization L?

A block of ice is at its melting point.

A mass m of water at temperature θ (in °C) is poured onto the ice and cools to 0 °C, melting some of the ice.

The specific heat capacity of water is c and the specific latent heat of fusion of ice is L.

Assuming all the heat lost by the water melts ice, what mass of ice melts?

Explain, in terms of the particle model, why most substances are denser as a solid than as a liquid.

Outline how the particle model accounts for a gas having no fixed shape and no fixed volume, while a solid has both.