K.C.S.E Physics Q & A - MODEL 2018PP1QN18

K.C.S.E Physics Q & A - MODEL 2018PP1QN18

​(a) State two quantities that must be kept constant in order to verify Boyle’s law. 
(b) An air bubble at the bottom of a beaker full of water becomes larger as it rises to the surface. State the reason why;
(i) the bubble rises to the surface,
(ii) It becomes larger as it rises. 
(c) State two assumptions made in explaining the gas laws using the kinetic theory of gases.
(d) Figure 11 shows an incomplete experimental set up that was prepared by a student to verify one of the gas laws.

(i) State with a reason which one of the laws may be verified using the set up.
(ii) State what the student left out in the diagram of the set up.
(c) The volume of a fixed mass of a gas reduced from 500 cm³ to 300 cm³ at constant pressure. The initial temperature was 90K. Determine the final temperature

answers

(a) Mass
 Temperature
(b)(i) The gas is less dense than the water. 
(ii) As it rises the pressure around the bubble reduces and since the temperature is the same, the volume increases. 
(c) The size of the molecules is assumed to be negligible. 
 Intermolecular forces are also assumed to be negligible. 
 Real gases can never have zero volume yet the gas laws assume presence of zero volume.
(d)(i) The pressure law. 
 Has ability to measure the temperature and the pressure while keeping the volume constant. 
(ii) Source of heating for the temperature to be changed.