CHAPTER 1.1 –
THE PROPERTIES OF WATER
I. THE STRUCTURE OF WATER
• Water’s chemical structure is made up of
atoms. Atoms are one of the smallest
structures on earth.
• If one puts atoms together, they form a
molecule.
• A combination of Atoms = One Molecule
• Water is composed of two hydrogen atoms
and one oxygen atom. This is known as
H2O.
• The molecules that make up water are
known as polar molecules. Polar
molecules are molecules that have either
a positive charge or negative charge at
their ends.
• Oxygen has a negative charge to it while
hydrogen has a positive charge. The
opposing charges causes oxygen and
hydrogen to stick together.
• This attraction is caused by an electric
force not a magnetic one.
II. KEY PROPERTIES OF WATER
• The four key properties of water are:
– 1.
– 2.
– 3.
– 4.
Capillary Action,
Surface Tension,
Ability to Dissolve Many Substances; and
High Specific Heat.
A. CAPILLARY ACTION
• Water molecules have the ability to stick to
walls of a surface and move upward in it.
Think of water rising up a straw.
• The combined forces of attraction among
water molecules and its surrounding
material are called CAPILLARY ACTION.
• Capillary action occurs not only with
material that has pores (such as paper
towels) but with material that has fibers
(ex. Dry wick clothes and socks).
B. SURFACE TENSION
• Definition of Surface Tension: the tightness
across the surface of water when polar
molecules pull on one another.
• Water molecules at the surface are being pulled
by water molecules around them and under
them. As a result, the pulling causes the water
at the surface to become curved in shape. (ex.
Water droplets on a car windshield)
B. SURFACE TENSION
• Definition of Surface Tension: the tightness
across the surface of water when polar
molecules pull on one another.
• Water molecules at the surface are being pulled
by water molecules around them and under
them. As a result, the pulling causes the water
at the surface to become curved in shape. (ex.
Water droplets on a car windshield)
C. UNIVERSAL SOLVENT
• Definition of a solution: a mixture that forms
when one substance dissolves into another
substance.
• Definition of solvent: a substance that can
dissolve another substance.
• Water is one of the best solvents on Earth
because the charged ends of the water molecule
can attract many other substances to it that also
have a charged end. Any charged substance is
called polar.
• If a substance does not have any charged
ends to it (this is called being nonpolar),
then water does not stick to it to dissolve
it.
• Water is called the “universal solvent”
because it can dissolve solids (like sugar),
liquids (like bleach), and gases (like
oxygen).
D. SPECIFIC HEAT
• - Definition of Specific Heat – the amount of heat
needed to increase the temperature of a
substance by 1 degree Celsius.
• Water has a very high specific heat; in other
words, it takes a lot of heat to have water
become warmer.
• The reason why more heat is needed is because
heat must break through the strong bonds of
attraction between the water molecules.
• Substances that have weak attraction bonds such
as air and sand can heat up more quickly. As a
result, air and sand have a low specific heat.
• Cities that border a large body of water do not
experience a dramatic temperature increase like
cities that have no water by them. (Think
Minooka vs. Honolulu).
• The water absorbs a lot of the heat keeping the
temperature fairly constant. Land and the air
above it absorb very little heat before the land
and air starts to heat up.
III. CHANGING STATE
• There are four states of matter: solid, liquid,
gas, and plasma.
• In a solid state, atoms are arranged in neat,
orderly rows and they move in place.
• In a liquid state, atoms slide over each other but
are still fairly close together.
• In a gas state, atoms are far apart and move at a
high rate of speed.
• In a plasma state, the atoms loose part of
themselves (the electrons) to expose its
nucleus (the center of the atom).
• Water is the only substance on earth that can
exist in all four states of matter. (Solid = ice;
Liquid = water; Gas = water vapor; and
Plasma = water plasma).
A. BOILING AND EVAPORATION
• When water is in the liquid state, it has
definite mass but no definite shape. It
takes the shape of the container it is in.
• When water is heated, the water
molecules move faster and faster as it
absorbs the heat. You can see this
movement and it is called boiling.
• At 100 degrees Celsius, water boils and
changes state from liquid to gas.
• A change of state from liquid to gas is
called evaporation (absorb energy). The
water molecules possess enough energy
to break from the surface of the liquid and
float into the air.
B. CONDENSATION
• When water vapor cools, the water
molecules release some of their energy
and slow down in movement.
• The slow down in water molecule
movement causes a decrease in
temperature.
• A change of state from gas to liquid is
called condensation (release energy).
C. FREEZING
• At 0 degrees Celsius, water changes state
from liquid to solid. The water molecules
give up more energy which forces them
into a rigid form (ice).
• - A change of state from liquid to solid is
called freezing (release energy).
D. MELTING
• Melting is a change of state from solid to
liquid (absorb energy).