Principle
The vapour pressure of water in the range of 40 °C to 85 °C is
investigated. It is shown that the Clausius-Clapeyron equation
describes the relation between temperature and pressure in an
adequate manner. An average value for the heat of vaporisation of
water is determined.
Benefits
- Compact, easily transportable setup
- For both demonstration and student experiments
- No gas burner required - Easy to operate and no consumption of consumables
- No open flame in the setup - Reduction of thermal hazard
Tasks
- About 250 ml of demineralised water are allowed to boil for
about 10 minutes to eliminate all traces of dissolved gas. The
water is then cooled down to room temperature.
- The 3-neck round flask is filled about three-quarters full with
gas-free water and heated. At 35 °C the space above the water
within the round flask is evacuated. Further heating causes an
increase in pressure p and temperature T of water within the
round flask. p and T are read in steps of 5 °C up to a maximum
of T = 85 °C.
What you can learn about
- Pressure
- Temperature
- Volume
- Vaporization
- Vapour pressure
- Clausius-Clapeyron equation
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