(b) An electric kettle is filled with 500 g of water and is initially at a temperature of 15 °C.
The kettle has a power rating of 2 kW.
(i) Calculate the energy required to raise the temperature of the water to 100 °C.
(ii) How much energy is supplied by the kettle every second? (iii) How long will it take the kettle to heat the water to 100 °C? (6)
(iv) Name a suitable material for the handle of the kettle. Justify your answer.
(specific heat capacity of water = 4180 J kg–1 K–1) 2008
7. A saucepan containing 500 g of water at a temperature of 20 °C is left on a 2 kW ring of an electric cooker until it reaches a temperature of 100 °C. All the electrical energy supplied is used to heat the water. Calculate:
(i) the rise in temperature of the water (ii) the energy required to heat the water to 100 °C (iii) the amount of energy the ring supplies every second (iv) the time it will take to heat the water to 100 °C.
(Q = mcDq, P = W/t, specific heat capacity of water = 4200 J kg–1 K–1)
2006 7. Explain how the storage heater heats the air in a room.
(8)
The total mass of the bricks in the storage heater is 80 kg and their specific heat capacity is 1500 J kg–1 K–1. During a ten-hour period the temperature of the bricks rose from 15 °C to 300 °C.
Calculate:
(i) the energy gained by the bricks (ii) the power of the heating coil. (Q = mcDq, P = W/t)
Higher Level 2011
7. (a) When making a hot drink, steam at 100 °C is added to 160 g of milk at 20 °C. If the final temperature of the drink is to be 70 °C, what mass of steam should be added? You may ignore energy losses to the surroundings.
A metal spoon, with an initial temperature of 20 °C, is then placed in the hot drink, causing the temperature of the hot drink to drop to 68 °C. What
