Water has unique properties
• It is made of molecules.
• Each molecule is made up of one atom of
oxygen and two atoms of hydrogen.
The main properties
• Density and dilation. The density of the ice is
lower than the density of the water. Ice floats
• A powerful solvent. It can dissolve many
– Can water dissolve grease, oil?
– Can water dissolve gases such as oxygen and
• It has a high specific heat. Water does not get
hot or cold easily.
– Water is an ideal substance to absorb and
– Water moderates the Earth´s climate.
Adhesion and cohesion
• Cohesion: Water is attracted
• The water drop is composed
of water molecules that like
to stick together
Adhesion: Water is attracted
to other substances
• Water drops on pine needles, showing the
effects of gravity, adhesion, and cohesion on
Cohesion is seen in the actual water drop—the water
molecules stick to each other, forming a drop.
Property of gravity, which is causing the water drops to roll
along the pine needle.
Property of adhesion is holding them, at least for now, to the
• Cohesion makes a water drop a drop
– The drop seems to have a "skin" holding it
– It turns out that this surface tension is the result
of the tendency of water molecules to attract one
• Capillary action seen as water climbs to
different levels in glass tubes of different
• The movement of water within the
spaces of a porous material due to the
forces of adhesion, cohesion, and
• Plants and trees
action (adhesion and
• Floating paper clip made of steel The high
surface tension helps the paper clip - with
much higher density - float on the water.
• the cohesive forces between liquid molecules
are responsible for the phenomenon known
as surface tension.
• Walking on water: Small insects
such as the water strider
(pondskater) can walk on water
because their weight is not
enough to penetrate the surface.
• Don't touch the tent!: Common tent materials
are somewhat rainproof
• But if you touch the tent material with your
finger, you break the surface tension and the
rain will drip through.