Physics 5054 · O Level · Transfer of thermal energy

Transfer of thermal energy — practice question

A student is examining how insulation affects the cooling rate of hot water in a beaker. He pours $250\text{ cm}^3$ of hot water into a beaker and inserts a thermometer into the water, as shown in Fig. 2.1. He waits for a brief period. He then starts a stopwatch as he measures the temperature $\theta$ of the hot water. This is at time $t = 0$. Fig. 2.2 shows the thermometer at $t = 0$.
(a(i))[1]

Use the thermometer reading and note the temperature $\theta$.

(a(ii))[1]

Explain why the student leaves a short time before measuring the water temperature at $t = 0$.

(b(i))[1]

Fill in the column headings in the table in Fig. 2.4.

(b(ii))[1]

Enter your value of $\theta$ from (a)(i) into the table in Fig. 2.4.

(b(iii))[1]

State whether the insulation has any significant effect on the rate of cooling in the first $3.0$ minutes. Justify your answer by referring to the results.

(c(i))[1]

At the start, evaporation is the main reason heat is lost from the beaker. Suggest how the student can reduce heat loss by evaporation.

(c(ii))[1]

State one further change to the apparatus in Fig. 2.3 that reduces the heat loss even more.

(d)[1]

State one quantity that is held constant to allow a fair comparison between the cooling rates of the two beakers.

Worked solution & mark scheme

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