Thermal Energy Transfer (AQA A Level Physics)

1.2 kg of water at 20 °C cools to 0 °C and then freezes to form ice, also at 0 °C. 

What is the energy released during this process?

   specific heat capacity of water = 4200 J kg^–1 K^–1
   specific latent heat of fusion of ice = 3.4 × 10⁵ J kg^–1

Heat energy is applied at a constant rate to a solid material with a specific heat capacity of 1.8 × 10³ J kg^-1 K^-1. The graph below shows how the temperature of the material varies with time as the solid melts and becomes a liquid.

What is the specific latent heat of fusion of the substance?

The temperature of 250 g of water decreases by 7.2 ^oC when placed in a fridge for 25 minutes.  This container is then removed and a second container with 350 g of water, at 22 ^oC, is placed in the same fridge for 30 minutes.  

Assuming that energy is lost at the same rate in both containers, what is the final temperature of the water in the second container after 30 minutes? 

The specific heat capacity of the water is 4200 J kg^-1 K^-1

An ideal gas is kept at a constant pressure of 1.3 x 10⁵ Pa.  When 24 J of heat energy is transferred to the gas its volume increases from 1.3 x 10^-4 m³ to 3.6 x 10^-4 m³. 

When the heat energy is transferred, the overall internal energy of the gas:

Which of the statements below is correct ?

An engine goes through 3200 cycles every minute. To maintain a constant working temperature, 126 J of energy must be removed by a coolant during each complete cycle of this engine. The temperature of the coolant rises by 22 °C as it passes through the engine.

Calculate the volume of the coolant that flows through the engine in one second.

        specific heat capacity of coolant = 3.8 × 10³ J kg^–1 K^–1

        density of coolant = 1.1 × 10³ kg m^–3

A beaker of water with a submerged immersion heater is placed on the right hand side of a two-pan balance. The immersion heater is used to boil water at 100 ^oC and is connected to a kWh meter. When the water starts to boil standard masses are then added to the left hand side of the two-pan balance so that it is in equilibrium with the beaker of water. The reading on the kWh meter when the two-pan balance is in equilibrium is 8.0 kWh. A 300 g mass is then added to the right hand side of the two-pan balance, causing it to tilt. As the water boils off, the right pan rises until equilibrium is restored. The reading on the kWh meter when this happens is 8.3 kWh.

If the immersion heater is 60% efficient, what is the specific latent heat of vaporisation of the steam?

The spring in a ball point pen has a mass 0.12 g and is made from a material with a specific heat capacity of 450 J kg^-1 K^-1. To extend or retract the nib of the pen a force of 1N is required to compress the spring by 4 mm. When the spring is released 10% of the strain energy stored is converted into heat energy in the spring. 

Assuming that there is no heat loss from the pen, calculate the number of times the spring must be compressed and released to cause the temperature of the pen to increase by 1^oC.