A student investigates how covering the surface of the water in a beaker affects the rate at which the water cools. Plan an experiment to investigate the relationship between covering the surface of water in a beaker and the rate at which the water cools.

Here is the plan for the experiment:

Diagram:
As an AI, I cannot draw a diagram directly. However, the diagram should show two identical setups side-by-side:

• Setup 1 (Uncovered): A $200 \text{ cm}^3$ beaker containing hot water. A thermometer is immersed in the water, held by a clamp stand (not explicitly listed but implied for stability) or simply shown upright in the water. A stopwatch is shown nearby.
• Setup 2 (Covered): An identical $200 \text{ cm}^3$ beaker containing the same volume of hot water. A thermometer is immersed in the water. The circular lid is placed on top of this beaker, covering the water surface. A stopwatch is shown nearby.

Both setups should indicate the initial temperature of the water.

Explanation of how to carry out the investigation:

• Step 1: Use the electric kettle to boil water.
• Step 2: Pour an equal volume (e.g., $150 \text{ cm}^3$) of hot water into each of the two $200 \text{ cm}^3$ beakers.
• Step 3: Place a thermometer into each beaker. Wait a short moment for the temperature to stabilize and ensure both beakers start at the same initial temperature (e.g., $90^\circ\text{C}$).
• Step 4: Place the circular lid on one of the beakers, ensuring it covers the water surface. Leave the other beaker uncovered.
• Step 5: Start the stopwatch simultaneously for both setups.
• Step 6: Record the temperature of the water in both the covered and uncovered beakers at regular time intervals (e.g., every $60 \text{ s}$) for a total duration of $10-15$ minutes.

State measurement you would take:

• The initial temperature of the water in both beakers.
• The temperature of the water in both beakers at regular time intervals.

Draw a table with column headings to show how you would display your readings:

Time / s	Temperature (Uncovered Beaker) / $^\circ\text{C}$	Temperature (Covered Beaker) / $^\circ\text{C}$
0
60
120
180
...

Explain how you would process your results:

• Step 1: Plot a graph of temperature (on the y-axis) against time (on the x-axis) for both the covered and uncovered beakers on the same set of axes.
• Step 2: Draw a smooth curve through the plotted points for each set of data.
• Step 3: Calculate the rate of cooling for each beaker by determining the gradient of the temperature-time graph at various points, or by comparing the total temperature drop over the entire duration.

Explain how you would use your results to reach a conclusion:

• By comparing the two cooling curves on the graph, the beaker with the steeper curve indicates a faster rate of cooling.
• If the curve for the uncovered beaker is steeper than that for the covered beaker, it means the uncovered water cooled faster.
• The conclusion would state whether covering the surface of the water increases or decreases the rate at which the water cools, based on which curve shows a slower temperature decrease over time.

State one key variable that you would control to ensure a fair test:

• The initial volume of water in both beakers.
• The initial temperature of the water in both beakers.
• The ambient room temperature.
• The material and size of the beakers.