Why Water Boils
* Water Boils at 100 oC at STP
To find out why water boils
To find out what all makes water
Put a random amount of water into
good sized beaker (400 or 600 mL)
Add heat by a Bunsen burner or a
To see the convection currents,
add an insoluble liquid to the
The stronger the attractive forces,
the higher the temperature at
which the liquid boils.
Water contains all three types of
Intermolecular forces, (Van der
Waals, dipole-dipole, and
Figure of the Dipole
Vapor Pressure - pressure exerted
by vapor when liquid and vapor are
Water boils when its vapor
pressure equals the external
pressure acting on the surface.
If the external pressure increases,
so does the vapor pressure.
Water’s vapor pressure is 760 torr
when water boils at at a temp of
When water is heated it becomes
less dense and rises.
This circulation accounts for the
uniform heating of water.
If the external air pressure would
be higher, water would boil at a
If water was not polar, it would boil
at a lower temperature.
Convection currents circulate the
water to allow for uniform heating.
What makes water boil on the
How convection currents aid the
The variation of boiling points at