Part(a). It was fairly well attempted as most candidates were able to list the effects
correctly.
Part (b)(i). Most candidates could not express their answers systematically as required.
It was poorly attempted.
Most responding candidates were able to answer this question. Many candidates considered low or insufficient friction on highly polished floor will make the can run with no easy. Performance was average.
Part(c) (i) Many candidates stated the pressure law correctly. However, few candidates did not take into consideration the importance of having “gas of fixed mass”;”at constant volume” and “absolute or Kelvin temperature” in their definition hence they lost marks.
(ii) Many candidates could not get the calculation. Most calculated using oC
instead of Kelvin. Few candidates could not convert the 559K to oC.
Performance was poor.
The expected answers are:
(a) Effects of heat
e.g. Change in:
- size (expansion/contraction)
- temperature
- colour
- state/phase
- electrical resistance.
(b)(i) Glass is a poor conductor of heat, so also water. When boiling water is poured into the glass cup, the inner layer/surface quickly expands while the outer layer/ surface remains at room temperature . Resulting unequal expansion between these layers /surfaces generates thermal stress in the cup , causing it to crack When the cup is immersed in cold water that is heated from room temperature to boiling point , the heating gradually raises the temperature of water and cup in succession and without the development of (appreciable) thermal stress in the cup . The temperature gradient across the wall of the cup is (negligibly) small at any point in time; hence cracking does not occur .
(ii) A highly polished floor is devoid of the friction needed for effective/ easy running of the cat
OR
(Sufficient) friction will enable the cat to run easily on a floor [1]. When the floor is highly polished the friction present is not enough to make the cat run easily
(c)(i) The pressure law states that at constant volume, the pressure of a fixed mass of (an ideal) gas is directly proportional to the absolute/Kelvin temperature
(ii) =
=
T2 = = 559K
= 559 – 273
= 286C