Questions on Specific heat capacity and Specific latent heat.
1) When a car brakes, an amount of thermal energy equal to 112 500 J is
generated in the brake drums. If the mass of the brake drums is 28 kg and
their specific heat capacity is 460.5 J kg-1K-1, what is the change in their
temperature?
2) A piece if iron of mass 200 g and temperature 300 °C is dropped into 1.00
kg of water of temperature 20 °C. What will be the eventual temperature
of the water? (Take c for iron as 470 J kg-1K-1 and for water as 4200 J kg1K-1? Hint: Remember, conservation of energy demands that thermal energy
lost = thermal energy gained.
3) Determine what is meant by the specific heat capacity of a substance.
Consider two metals that have different specific heat capacities. The
thermal energy required to increase the temperature of 1 mol of
aluminium and 1 mol of copper by the same amount are about the saem.
Yet the specific heat capacities of the two metals are very different.
Suggest a reason for this.
4) A car of mass 1360 J descends from a hill of height 86 m at a constant
speed of 20 km h-1. Assuming that all the potential energy of the car goes
into heating the brakes, find the rise in the temperature of the brakes.
(Take the heat capacity of the brakes to be 16 kJ K-1 and ignore any
thermal energy losses to the surroundings.)
5) The water in an iron pipe has frozen to ice at -4.8 °C. The heat capacity of
the pipe is 7.1 kJ K-1. The volume of ice in the pipe is 12.3 L. What is the
combined heat capacity of the pipe and ice? To melt the ice, a heater of
power output 4.99 kW is connected to the pipe. How long will it take for
the ice to melt? (Density of ice = 0.929 kg L-1; specific heat capacity of ice
= 2.20 kJ kg-1 K-1; latent heat of fusion of ice = 334 kJ kg-1 K-1)
6) How much ice at -10 °C must be dropped into a cup containing 300 g of
water at 20 °C in order for the temperature of the water to be reduced to
10 °C? The cup itself has a mass of 150 g and is made out of aluminium.
Assume that no thermal energy is lost to the surroundings.
7) The surface of a pond of area 20 m2 is covered by ise of uniform thickness
6 cm. The temperature of the ice is -5 °C. How much thermal energy is
required to melt this amount of ice into water at 0 °C? (Take the density of
ice to be 900 kg m-3.)
8) (a) How much thermal energy is required to warm 1.0 kg ice initially at 10 °C to ice at 0 °C?
(b) How much thermal energy is required to melt the ice at 0 °C?
(c) How much thermal energy is required to further increase the
temperature of the water from 0°C to 10 °C?
(d) In which stage (warming the ice, melting the ice, warming the warer)
is the thermal energy required the largest?
9) Ice at 0 °C is added to 1 L of water at 20 °C, cooling it down to 10 °C. How
much ice was added?