OCR A-Level Physics B H557
Planning
Implementing
Analysis
Evaluation
Practical Skills
Use of Apparatus and Techniques
Fundamental Data Analysis
Imaging and Signalling
Sensing
Mechanical Properties of Materials
Waves and Quantum Behaviour
Space, Time and Motion
Creating Models
Out Into Space
Our Place in the Universe
Matter: Very Simple
Matter: Hot or Cold
Electromagnetism
Charge and Field
Probing Deep Into Matter
Ionising Radiation and Risk
Matter: Very Simple
Investigating the gas laws and absolute zero
- 3 things to know
- Components 01, 02 and 03
Overview
Recall questions on estimating absolute zero from constant-volume pressure readings and why it needs extrapolation, control variables, thermal equilibrium and stirring, the trapped-air experiment and column length as volume, plotting p against 1/V, pressure monitors with data loggers, changing pressure slowly, the main systematic error, gauge pressure, rising and falling readings, and the effect of a leak.
What you need to know
Answer each one before you reveal it.
Describe how a fixed mass of gas can be used to estimate the value of absolute zero.
What temperature-axis intercept confirms a successful determination of absolute zero?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe how a fixed mass of gas can be used to estimate the value of absolute zero.
Model answer
The pressure of gas held at constant volume is measured at several bath temperatures, pressure is plotted against temperature in degrees Celsius, and the straight line is extrapolated back to zero pressure.
- 2
What temperature-axis intercept confirms a successful determination of absolute zero?
Model answer
The extrapolated line should meet the temperature axis at about −273 °C.
- 3
Name the control variables in a constant-volume investigation of pressure against temperature.
Model answer
The mass of gas and the volume it occupies must both be kept constant.
- 4
Why must the gas be left for a time after each change of bath temperature?
Model answer
The gas needs to reach thermal equilibrium with the bath, otherwise the recorded temperature is not the temperature of the gas.
- 5
Why is the water bath stirred throughout?
Model answer
Stirring keeps the temperature uniform so that the thermometer reads the temperature the gas is actually at.
- 6
Describe how the relationship between the volume and the pressure of a gas is investigated in the laboratory.
Model answer
A fixed mass of air is trapped in a uniform tube above oil or behind a piston, the pressure is changed with a pump and read from a gauge, and the length of the trapped column is measured for each pressure.
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