2.3 Transfer of thermal energy

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Question 26

A student investigates the cooling of water under different conditions.

The room temperature is measured as $θR=22.0∘C\theta_{\text{R}} = 22.0^{\circ}\text{C}$ .

In the first experiment:

The student pours $cm3150\text{ cm}^3$ of hot water into an uninsulated beaker.
The temperature $θ1\theta_1$ is recorded at time $0\text{ s}$ and $150\text{ s}$ .

The readings are shown in Table 1.1:

∘C086.015071.0\begin{array}{|c|c|} \hline t \text{ / s} & \theta_1 \text{ / }^{\circ}\text{C} \\ \hline 0 & 86.0 \\ \hline 150 & 71.0 \\ \hline \end{array}

In the second experiment:

The student mixes $cm3100\text{ cm}^3$ of hot water with $cm350\text{ cm}^3$ of cold water in the beaker.
The temperature $θ2\theta_2$ is recorded at time $0\text{ s}$ and $150\text{ s}$ .

The readings are shown in Table 1.2:

∘C062.015054.5\begin{array}{|c|c|} \hline t \text{ / s} & \theta_2 \text{ / }^{\circ}\text{C} \\ \hline 0 & 62.0 \\ \hline 150 & 54.5 \\ \hline \end{array}

(i) Calculate the temperature drop $Δθ1\Delta\theta_1$ between $t = 0$ and $150\text{ s}$ for the first experiment.

(ii) Calculate the average rate of cooling $R_1$ of the water during this time using the equation $R1=Δθ1ΔtR_1 = \frac{\Delta\theta_1}{\Delta t}$ , where $s\Delta t = 150\text{ s}$ . Include the unit.

[2]

(i) Calculate the temperature drop $Δθ2\Delta\theta_2$ between $t = 0$ and $150\text{ s}$ for the second experiment.

(ii) Calculate the average rate of cooling $R_2$ of the water during this time using the equation $R2=Δθ2ΔtR_2 = \frac{\Delta\theta_2}{\Delta t}$ , where $s\Delta t = 150\text{ s}$ . Include the unit.

[2]

A student suggests that the rate of cooling $R$ depends on the difference $D$ between the initial temperature of the water (at $t = 0$ ) and room temperature $θR\theta_{\text{R}}$ .

(i) Calculate the difference $D_1$ for the first experiment using $D1=θ1(t=0)−θRD_1 = \theta_{1(t=0)} - \theta_{\text{R}}$ .

(ii) Calculate the difference $D_2$ for the second experiment using $D2=θ2(t=0)−θRD_2 = \theta_{2(t=0)} - \theta_{\text{R}}$ .

(iii) State whether the results support the suggestion. Justify your answer by making direct reference to your calculated values of $D_1$ , $D_2$ , $R_1$ , and $R_2$ .

[3]

(i) Explain why the thermometer scale should be read with the line of sight perpendicular (at right angles) to the scale.

(ii) Explain why the mixture of hot and cold water should be stirred before taking the temperature reading at the start of the second experiment.

[2]

A student investigates the cooling of water under different conditions.

The room temperature is measured as $θR=22.0∘C\theta_{\text{R}} = 22.0^{\circ}\text{C}$ .

In the first experiment:

The student pours $cm3150\text{ cm}^3$ of hot water into an uninsulated beaker.
The temperature $θ1\theta_1$ is recorded at time $0\text{ s}$ and $150\text{ s}$ .

The readings are shown in Table 1.1:

∘C086.015071.0\begin{array}{|c|c|} \hline t \text{ / s} & \theta_1 \text{ / }^{\circ}\text{C} \\ \hline 0 & 86.0 \\ \hline 150 & 71.0 \\ \hline \end{array}

In the second experiment:

The student mixes $cm3100\text{ cm}^3$ of hot water with $cm350\text{ cm}^3$ of cold water in the beaker.
The temperature $θ2\theta_2$ is recorded at time $0\text{ s}$ and $150\text{ s}$ .

The readings are shown in Table 1.2:

∘C062.015054.5\begin{array}{|c|c|} \hline t \text{ / s} & \theta_2 \text{ / }^{\circ}\text{C} \\ \hline 0 & 62.0 \\ \hline 150 & 54.5 \\ \hline \end{array}

2.3 Transfer of thermal energy

Question 26

Markscheme

2.3 Transfer of thermal energy

Question 26

Markscheme

2.3 Transfer of thermal energy

Question 26

2.3 Transfer of thermal energy Questions

2.3 Transfer of thermal energy

Question 26

2.3 Transfer of thermal energy Questions