A student is investigating the rate of cooling of water under different conditions. A greater rate of cooling occurs if there is a greater change in the temperature during the same period of time.
Fig. 3.1 shows some of the apparatus.
The thermometer in Fig.3.2 shows the room temperature θR at the beginning of the experiment. Record θR in °C.
θR = ........................................................
The student pours 200 cm3 of hot water into the beaker.
She records the temperature θ of the hot water at time t = 0. She immediately starts a stopclock.
She continues recording the time and the temperature readings every 30 s. The readings are shown in Table 3.1.
Table 3.1
Beaker
t / | θ / |
0 | 94 |
30 | 93 |
60 | 92 |
90 | 91 |
120 | 90 |
150 | 89 |
Table 3.2
Can
t / | θ / |
0 | 93 |
30 | 91 |
60 | 90 |
90 | 89 |
120 | 88 |
150 | 87 |
The student repeats the procedure using a metal can, painted matt black, in place of the beaker.
The readings are shown in Table 3.2.
(i) Complete the column headings in Table 3.1 and in Table 3.2.
[1]
(ii) Look carefully at the readings in Table 3.1 and in Table 3.2.
Tick the box to show your conclusion from the readings.
The water in the beaker has a greater rate of cooling than the water in the can.
The water in the beaker has a smaller rate of cooling than the water in the can.
There is no significant difference between the rates of cooling of the water in the beaker and the can.
[1]
(iii) Justify your conclusion by reference to the readings.
[2]
A student in another school carries out the experiment and reports that the rate of cooling of the water in the can is different from the rate of cooling of the water in the beaker. He plans a change to the experiment to find out whether this difference in the rates of cooling is caused by
the matt black surface of the can being a better radiator of thermal energy than the shiny surface of the beaker
the metal of the can being a better conductor of thermal energy than the material of the beaker.
(i) Suggest two suitable changes to the apparatus that the student could make.
[2]
(ii) Suggest two variables that should be controlled in order to make the experiment a fair test.
[2]
State one precaution that you would take in order to record accurate temperature readings.
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