O-LevelPhysicsThermal Physics5054/31 · May/June 2023 · Q110 Marks

In this experiment you will investigate specific heat capacity. You are provided with: • a 100 cm³ beaker labelled A with a mark at the 25 cm³ level • a beaker of water labelled B • a thermometer • access to a 50 g mass at 100°C.

(a)Pour 25 cm³ of water from beaker B into beaker A. Measure and record the temperature θ₁ of the water. Place the thermometer back on the bench. θ₁ = ...................................... °C[1]
(b)(i)The supervisor has placed some 50 g masses in boiling water. Each mass has been tied to a length of string. Take beaker A to where the masses are in boiling water. Using the string, remove one mass from the boiling water and place it carefully in the beaker. Do not touch the mass. Allow the string to hang over the side of beaker A and return beaker A to your workstation. (i) Measure and record the maximum temperature θ₂ of the water in beaker A. θ₂ = ...................................... °C[1]
(b)(ii)Describe how you make sure that your value of θ₂ is as accurate as possible.[2]
(b)(iii)Beaker A has a capacity of 100cm³ and beaker B has a capacity of 250cm³. Explain why beaker A is more suitable for this experiment than beaker B.[1]
(b)(iv)Calculate the specific heat capacity cm of the 50g mass using the equation: cm = 2.1 (θ₂ – θ₁) (100 – θ₂) Show your working. cm = ...................................... J/(g°C)[1]
(c)(i)Describe two sources of error in the method used to determine cm. 1 2[2]
(c)(ii)Suggest two improvements to the method. 1 2[2]

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[1] (a) candidate's value (°C) ;
[1] (b)(i) At least 5 degrees higher than candidate's value in 1(a) but no more than 20 degrees higher;
[2] (b)(ii) Any two from: wait to take the reading until the reading just begins to fall and note the maximum value observed; record to nearest 0.5 °C; stir/agitate the water to spread the heat evenly; thermometer in contact with the water only; (avoid parallax error by) viewing the reading / scale of the thermometer perpendicularly ;;
[1] (b)(iii) more accurate measurement of vol. / more water depth to cover the mass (or thermometer bulb) ;
[1] (b)(iv) award mark for correct substitution if cm is in range from 0.2 to 0.5 (J / (g °C)) ;
[2] (c)(i) Any two from: the string has heat capacity; the water in the string has heat capacity; the glass in the beaker has heat capacity; heat loss from mass during transfer/mass is less than 100 °C when it enters water; the mass transfers heat to glass (by conduction); heat loss from beaker / water cools down (by convection); not enough water to cover the mass; not enough water to fully immerse the thermometer bulb; temperature change is small ;;
[2] (c)(ii) Any two from: use non-absorbent string; put a lid on the beaker; insulate the beaker / wrap the beaker ; use the heat capacity of the glass beaker and modify the equation to allow for this; use more water to completely cover the mass and use a modified equation; transfer mass as quickly as possible ;;

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