O-LevelPhysicsThermal Physics5054/42 · May/June 2024 · Q210 Marks

A student investigates the rate of cooling of hot water in a test-tube under different conditions. (a) The student: • arranges a test-tube as shown in Fig. 2.1 test-tube stand Fig. 2.1 • pours 200 cm³ of cold water into a beaker • pours hot water into the test-tube until it is approximately one-third full • lowers the test-tube into the beaker of cold water until the level of the hot water in the test-tube is below the level of the cold water in the beaker as shown in Fig. 2.2 • places a thermometer into the test-tube • waits for approximately 30s before measuring the temperature and starting a stop-watch. The student measures the temperature θ of the hot water in the test-tube. The thermometer reading is shown in Fig. 2.3 180 70 60 Fig. 2.3 Read the thermometer and record the temperature in Table 2.1 at time t = 0.

(a)Read the thermometer and record the temperature in Table 2.1 at time t = 0.[1]
(b)(i)The student measures the temperature θ of the hot water every 30s for a further 180s. The readings are shown in Table 2.1. Complete the column headings by adding appropriate units.[1]
(b)(ii)Complete the time column.[1]
(c)Describe in detail one precaution that the student must take to make sure that the temperature measurements are as accurate as possible.[1]
(d)(i)The student repeats the procedure in (a) and (b) but with 200cm³ of warm water instead of cold water in the beaker as shown in Fig. 2.4. stand beaker hot water warm water Fig. 2.4 The student's readings with warm water are shown in Table 2.1. One of the student's readings for warm water recorded in Table 2.1 is anomalous. Identify the anomalous temperature reading and explain how you decided that the reading is anomalous.[2]
(d)(ii)Use the temperature readings in Table 2.1 to calculate the temperature decrease of the hot water in the test-tube after cooling for 180s in both the beaker of cold water and the beaker of warm water.[1]
(e)(i)Use your answers to (d)(ii) to decide how the temperature of the water in the beaker affects the rate of cooling of hot water in the test-tube. State your conclusion.[2]
(e)(ii)Suggest one improvement to the experimental procedure described in (a) and (b) that allows a more valid comparison to be made between the two rates of cooling.[1]

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Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

[1] 2(a) 73(.0) (°C);
[1] 2(b)(i) s, °C, °C;
[1] 2(b)(ii) 30, 60, 90, 120, 150, 180;
[1] 2(c) read thermometer scale at right angles / eye level / place stopwatch close to test-tube / stir before reading / thermometer not touching the sides / base of the test-tube / thermometer one-third or one-half immersed in the test-tube ;
[1] 2(d)(i) 35 (°C) / reading at 150 (s);
[1] 2(d)(i) it doesn't follow the trend / pattern / the reading is much lower than the one following / because the following reading is much higher;
[1] 2(d)(ii) 39, 23 (°C)
[1] 2(e)(i) in cold water – larger temperature difference / rate of cooling is greater ;
[1] 2(e)(i) temperature values used to justify the statement; or two rates calculated (and compared);
[1] 2(e)(ii) same initial temperatures / (use a measuring cylinder to) add equal volumes / amounts of hot water to the test-tube in both cases/lag the beaker / carry out both experiments at the same time ;

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