(iii) Calculate a value for the specific latent heat of vaporisation of water. The specific heat capacity of copper is 390 J kg1 K1 and the specific heat capacity of water is 4 180 J kg1 K1.
(iv) A thermometer with a low heat capacity was used to ensure accuracy. Explain why. (v) Give one other precaution that should be taken to prevent heat loss from the calorimeter.
‘SECTION B’ SHORT QUESTION
Typical of Question 5 in Leaving Cert. Exam
Q5 Answer all of the following parts (a), (b), (c), etc. (a) What is the average amount of energy falling normally on each square metre of the Earth’s atmosphere in one day, given that the solar constant is 1.35 kW m2?
(b) On a very hot day a non-physicist decided to leave the refrigerator door open in order to cool the kitchen.Why did this warm up the room rather than cool it?
(c) How does perspiring help cool the body down during exercise?
(d) What is the name given to the tendency of water to circulate as it is heated? (e) What is meant by conduction?
(f) An electric toaster heats bread by convection and radiation. Give two differences between convection and radiation as a means of heat transfer
(g) The U-value of a house is a measure of the rate of heat loss to the surroundings. Give two ways in which the U-value of a house can be reduced.
(h) Sausages being cooked under a grill are primarily heated by radiated heat. Justify this claim.
(i) A steam burn will cause a more severe scald than the same mass of water, even when both have a temperature of 100 C. Explain.
(j) Why are light-coloured clothes more effective at keeping you cool on a hot day than dark- coloured clothes?
‘SECTION B’
FULL QUESTION Q6 Define specific latent heat.
What is the difference between latent heat of fusion and latent heat of vaporisation?
Freezers and refrigerators use heat pumps to remove heat from their compartments. Why are heat pumps necessary? Explain briefly how they work.
Three ice cubes, each of mass 4 g and temperature 10 C, are placed in a glass of water. The initial temperature of water was 21.1 C; it was 15 C after all the ice was melted. Assume no heat is lost to the
