O-LevelPhysicsThermal Physics5054/22 · May/June 2014 · Q1015 Marks

Two metal saucepans contain the same mass of hot water at the same initial temperature. Pan A is white and pan B is black, but otherwise the two saucepans are identical. Both saucepans are uncovered and cool under the same conditions. The cooling curves for the two saucepans are shown in Fig. 10.1. [Figure 10.1]

(a)(i)Describe how the water in a pan loses heat by conduction,[2]
(a)(ii)Describe how the water in a pan loses heat by convection.[2]
(b)(i)Explain why pan B cools faster than pan A.[1]
(b)(ii)Describe and explain how Fig. 10.1 is different when the pans are covered and the experiment is repeated.[2]
(c)(i)The specific heat capacity of water is 4200J/(kg°C). Explain what is meant by specific heat capacity.[2]
(c)(ii)The specific heat capacity of water is very high. Suggest one disadvantage of this when water is used for cooking.[1]
(c)(iii)1.The water in pan A cools for 8 minutes, as shown in Fig. 10.1. During this time, the water loses an average of 9000 J of thermal energy per minute. Calculate the mass of water in pan A.[3]
(c)(iii)2.The mass of water in pan B is the same as that in pan A. Calculate the thermal energy lost from the water in pan B during the 8 minutes.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2014). The mark or mark type is shown in brackets.

[B1] (a) (i) (conduction occurs) through or in metal/pan or from water to metal/pan or molecules vibrate or molecules collide or (free) electrons (in metal) move
[B1] vibration/energy/heat passed from molecule to molecule clear or energy passed on by electrons colliding (with atoms/molecules or electrons)
[B1] (ii) hot air or air over water rises or hot water rises
[B1] hot air or hot water expands or hot air or water less dense
[B1] (b) (i) black objects radiate heat more (than white)
[B1] (ii) (both) graphs higher (after start) or temperature falls less (in same time)/slower or takes longer to cool
[B1] less evaporation occurs or less convection
[C1] (c) (i) heat/energy to change the temperature by 1°C/unit temp
[A1] heat/energy to change the temperature of 1 kg/unit mass by 1°C/unit temp
[B1] (ii) long time to warm/boil water/cook or scalds/burns when touched or more energy needed (to warm water)
[C1] (iii) 1. 34(°C) or 94–60 seen
[C1] (m=) Q/cΔT algebraic or numerical with any clear Q or ΔT
[A1] 0.5(042) kg
[C1] 2. 0.50 x 4200 × 54
[A1] 110 000 or 114(353) J

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.