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This question is about an experiment to estimate absolute zero - AQA - A-Level Physics - Question 3 - 2018 - Paper 3
Question 3
This question is about an experiment to estimate absolute zero. Figures 9a to 9d show the stages in the procedure carried out by a student. An empty flask fitted w... show full transcript
Worked Solution & Example Answer:This question is about an experiment to estimate absolute zero - AQA - A-Level Physics - Question 3 - 2018 - Paper 3
Step 1
Explain why the volume of the air in the flask in Figure 9c is less than the volume of the air in the flask in Figure 9d.
Answer
The volume of the air in the flask in Figure 9c is less than in Figure 9d because, in Figure 9c, the water enters the flask, displacing some of the air. Consequently, the pressure of the air increases as the amount of space occupied by the air decreases.
Step 2
Explain why Charles's Law can be applied to compare the air in the flask in Figure 9c with the air in the flask in Figure 9d.
Answer
Charles's Law states that the volume of a gas is directly proportional to its temperature when pressure is held constant. In this experiment, the air temperature before and after the water enters can be treated as constant for each flask, allowing for direct comparison under the assumption of equal pressure conditions.
Step 3
Explain how V1 and V2 can be determined.
Answer
To determine V1 and V2, the following method can be used:
- Use a measuring cylinder to accurately measure the volume of water that the flask holds when completely filled (for V2).
- Measure the amount of water left in the cylinder after submerging the flask to find V1.
- Ensure all measurements are taken at eye level to avoid parallax errors.
Step 4
Plot on Figure 11 points to show the volume V' and the temperature θ of the air in the flask when the flask is as shown in Figure 9a and the flask is as shown in Figure 9d.
Answer
Plot the two sets of data:
- For the flask in Figure 9a, record the temperature (86 °C) and the corresponding volume (48 cm³).
- For the flask in Figure 9d, record the room temperature (19 °C) and the corresponding volume (255 cm³). Then plot these values on the graph provided in Figure 11.
Step 5
Add a best fit line to your graph in Figure 11 to show how V' should vary with θ according to Charles's Law.
Answer
Draw a straight line that best represents the trend of the plotted points, indicating that as the temperature increases, the volume also increases, consistent with Charles's Law.
Step 6
Determine the value of absolute zero in °C using your graph in Figure 11.
Answer
Extend the best fit line until it intersects the temperature axis. The temperature at which the volume would theoretically be zero represents absolute zero. For accurate measurement, read the temperature marked at this intersection.