pressure & temperature

The pressure in a sealed container changes with temperature. These changes can be monitored using sensors attached to the computer. A graph of pressure against temperature can be plotted as the changes occur. After the experiment, the scale of the axis can be changed to estimate Absolute Zero.

What you need
Water bath, flask with bung, delivery tube, interface, temperature and pressure sensors.

You may feel it is important to use dry air. If so, flush the flask with dry air, then seal it before doing the experiment.

Connect the pressure sensor to the first socket on the interface and the temperature sensor to the second socket. If the sensors are adjustable, set a 10kPa range on the pressure sensor and a 0-100°C range on the temperature sensor.
Start your sensing software, with luck it will recognise the sensors you attach automatically, otherwise, you will have to change the set-up yourself.
Set your sensing software to record for 10 minutes. Start recording and then heat the flask. After 5 minutes allow it to cool.

Questions

  • What does the graph tell you about the change in pressure?
  • What does the graph tell you about the change in temperature?
  • Use the software to plot the pressure against the temperature.
  • What seems to be the pattern between pressure and temperature?
  • Set the temperature axis to include absolute zero and extrapolate the graph down to absolute zero.

Teacher question

How could you succeed in finding absolute zero in this experiment? Your software may allow you to plot the pressure against temperature as the experiment proceeds rather than afterwards. Is this approach better?

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