y12 Homework

Latent Heat

Latent Heat of fusion of ice = 3.36 x 105 J kg-1
Latent Heat of vaporization of water = 2.25 x 106 J kg-1
Specific heat capacity of water = 4200 J kg-1 K-1

How much heat energy is needed to change 0.010 kg of water at 20oC to steam at 100oC?
How much heat energy is needed to change 0.020 kg of ice at 0°C into steam at 100°C?
How much heat energy is needed to melt 0.010 kg of ice at 0o C and then heat the water formed to 20o C?
What mass of ice at 0 °C is needed to cool 0.086 kg of water from 54 °C to 6 °C?
When a kettle boils a space can be seen between the spout and the so called `cloud of steam'. If your finger were placed in the space a much more serious scald would result than if it were placed in the `cloud of steam'. Explain why, and criticize the expression `cloud of steam'.
A heating coil takes 14 min to heat 0.20 kg of water from 20 °C to boiling point. How much longer will it take to boil away 0.02 kg of the boiling water?
A 1 kW immersion heater takes 225 s to boil away 0.1 kg of water at 100 °C. Find the specific latent heat of vaporization of water.
How long will it take an immersion heater of power 500 W to boil away a mixture of 0.05 kg of water and 0.02 kg of ice initially at 0 °C?
A mixture of ice and water at 0 °C contains 0.060 kg of ice. A 750 W immersion heater takes 26.8 s to melt all the ice. Deduce a value for the specific latent heat of fusion of ice.
A mixture of ice and water at 0 °C has a total mass of 1 kg, and con­tains 0.5 kg of ice. An immersion heater melts all the ice in 168 s, and then needs a further 84 s to heat the mixture to 20 °C. Find the specific latent heat of fusion of ice.
A vessel of heat capacity 115 J K-1 contains 0.30 kg of water and 0.20 kg of ice at 0 °C. An immersion heater takes 134.4 s to melt the ice and a further 88.6 s to heat the vessel and its contents to 20 °C. Find the specific latent heat of fusion of ice.
A heating coil takes 115 s to heat 0.05 kg of a liquid from 20 °C to its boiling-point of 80 °C. It needs a further 340 s to boil away 0.02 kg of the liquid. If the specific heat capacity of the liquid is 2300 J kg-1 K-1, find its specific latent heat of vaporization.