Figure 7 shows cavity wall insulation being installed in the wall of a house - AQA - GCSE Physics Combined Science - Question 5 - 2018 - Paper 1

To find the temperature inside the house after 30 minutes, we refer to the table provided:

• At 20 minutes, the temperature is 20.8 °C.
• At 40 minutes, the temperature decreases to 17.4 °C.

Now, we can perform a linear interpolation to estimate the temperature at 30 minutes:

$T = \frac{20.8 + 17.4}{2} = 19.1 \text{ °C}$

Therefore, the temperature inside the house after 30 minutes is approximately 19.1 °C.

The boiler converts different forms of energy in the following ways:

1. The chemical energy store of the fuel decreases as it is burned to produce heat.

2. The thermal energy store of the water increases as it absorbs heat from the combustion process, raising its temperature.

3. Additionally, the thermal energy store of the surrounding air or atmosphere can also increase as hot exhaust gases are released, warming the air.

To calculate the power of the boiler, we use the formula:

$P = \frac{E}{t}$

Where:

• $E$ is the energy transferred (in joules) = 15 MJ = 15,000,000 J.
• $t$ is the time taken (in seconds) = 10 minutes = 600 seconds.

Now substituting the values:

$P = \frac{15,000,000 \text{ J}}{600 \text{ s}} = 25,000 \text{ W}$

Thus, the power of the boiler is 25,000 W.