Water’s Unique Structure
 Like all matter, water is made up of atoms.
 Just as the 26 letters of the alphabet
combine in different ways to form all the
words in the English Language, about 100
types of atoms combine in different ways to
form all types of matter.
 Atoms attach together, or bond, to form
molecules.
Water’s Unique Structure
 Two hydrogen atoms bonded to an
oxygen atom form a water molecule.
 A short way writing this is to use the
chemical formula for water, H2O.
Water’s Unique Structure
 Each end of the molecule has a slight
electric charge.
 The oxygen end has a negative charge.
 The hydrogen ends has a positive
charge.
 A molecule that has a electrically
charged areas is called a polar
molecule.
Water’s Unique Structure
The positive hydrogen ends of one
water molecule attract the negative
oxygen ends of nearby water
molecules. As a result, the water
molecules tend to stick together.
Many of water’s unusual properties
occur because of this attraction.
Properties of Water
 Polarity
 Cohesion
 Adhesion
 Capillary Action
 Universal Solvent
 Surface Tension
 Density
 Specific Heat
Polarity
 Polarity is an uneven distribution of
charges across a water molecule.
 Water has unequal charges, therefore it is a
polar molecule.
 It attracted to itself and other molecules
carrying a charge.
 Polarity causes water to have all the other
properties.
Cohesion, Adhesion & Capillary
Action
 Cohesion is when water molecules are
attracted to other water molecules.
 Adhesion is when water molecules are
attracted to other substances
 Capillary Action is when cohesion and
adhesion is occurring and water molecules
are moving through a substance
 http://www.youtube.com/watch?v=oAY3yI
Sf-24
Universal Solvent
 A solution is a mixture that forms when
one substance dissolves another substance.
 The substance that does the dissolving is
called a solvent.
 For example making lemonade from a
powdered mix.
 Water is the solvent
 The two mixed together is the solution
Universal Solvent
 Water is a universal solvent because it will
dissolve anything with a charge (polar).
 The charged ends of the water molecule attract
the molecules of other polar substances.
 If the substance does not have a charge water
will not dissolve it. For example water/oil
 This property of water is one reason why water
encountered on earth is rarely pure.
Surface Tension
 Surface tension is the tightness across the surface
of water that is caused by the polar molecules
pulling on each other.
 The molecules at the surface are being pulled by
the molecules next to them and below them.
 This pulling forces the surface of the water to
have a curved shape.
 http://www.youtube.com/watch?v=whukr452ZvY
Density
 Density is referring to high tightly packed the
molecules are.
 The density of water is 1.0 g/L
 Ice floats on water because it is less dense than
water.
 Any substance that has a density less than 1.0
g/L will float.
 Any substance that has a density more than 1.0
g/L will sink.
Specific Heat
 Specific heat is the amount of heat needed
to move one gram of water one degree C.
 Water has a high specific heat.
 This means that it takes a long time for
water to heat up and to cool down.
 For example the water temperature at the
beach is always different the air
temperature.
Facts about Water
 Water is the only substance on Earth that occurs
naturally as a solid, liquid and a gas.
 Water covers 71% of Earth’s surface.
 Most water 97% of it is not drinkable(saltwater).
 The majority of freshwater (3%) exits in ice caps,
glaciers, and oceans.
 77% of freshwater is frozen
 Of the 23% that is not frozen, approximately a
.5% percent is available to supply living
organisms with what they need to survive.