**Specific Heat Capacity and Latent Heat** Questions - GCSE standard

**Q1. **An electrical immersion heater supplies heat at a steady rate to 2.5 kg of water at 20°C in a container of thermal
capacity 1500 J/K and it is noticed that in 8.0 minutes the temperature of the water rose to 100°C.

After another
hour, the water was just boiled away.

**(a)** Calculate the rate at which energy is supplied by the heater.

*(Specific heat capacity of water = 4200 J/kg K) *

**(4 marks)**

**(b) **What value does this experiment give for the specific latent heat of vaporisation of water?

**(2 marks)**

**(c)** The quoted value for the specific latent heat of vaporisation of water is 2.3 x 10^{6} J/kg. Explain why the experimental result value differs from this.

**(2 marks)**

**(Total 8 marks)**

**Q2**. An electric kettle of thermal capacity 820 J/K contains 0.90 kg of water.

If it takes 9.0 min to raise the temperature of the kettle and its contents from 19°C to 100°C, how much longer should it take to boil away half the water?

*(Specific heat capacity of water = 4200 J/kg K *

**Latent heat of vaporisation of water = 2.3 x 10**^{6} J/kg)

**(5 marks)**