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