Properties of Water
Water Polarity
• Water’s chemical formula is H2O
• The hydrogen atoms are “attached” to one
side of the oxygen atom.
• This results in a positive charge on the
hydrogen side and a negative charge on the
oxygen side of the atom.
Water Polarity Continued
• The uneven distribution of charge is called
polarity.
• Even though the poles of the molecule are
charged, a water molecule has an overall
charge of zero.
Hydrogen Bonds
• The slightly positive charge on the hydrogen of
a water molecule causes hydrogen to attract
slightly negative charged poles of molecules
Hydrogen Bonds Continued
• Hydrogen bonds hold water molecules
together
• Each water molecule can form a maximum of
4 hydrogen bonds
• Hydrogen bonding gives water some of its
extraordinary qualities:
– Cohesive behavior
– Resists changes in temperature
– High heat of vaporization
– Expands when it freezes
Cohesion
• Cohesion is the attraction between molecules
of the same substance.
• Water’s cohesion is responsible for molecules
on the surface of water being drawn inward.
This explains how insects walk on water.
• Cohesion also helps water combat the force of
gravity, allowing water to move through the
roots and up the stem of a plant.
Adhesion
• Adhesion is the attraction between molecules
of different substances
• Adhesion helps water adhere (stick) to the
walls of vessels, aiding a plant in drawing
water out of the roots and up the stem.
**Adhesion and Cohesion work together to
allow for water movement against gravity in
plants. This is known as capillary action.
How do you think you would explain how these
properties of water aid blood in traveling
throughout the body?
Surface Tension
• Surface tension is a measure of the force
necessary to stretch or break the surface of a
liquid
• This tension causes water to bead up on
surfaces (glass, fabric)
• The adhesion and cohesion properties of
water are responsible for causing surface
tension.
Specific Heat is the amount of heat that must be
absorbed or lost for one gram of a substance to change
its temperature by 1oC.
Three-fourths of the earth is covered
by water. The water serves as a
large heat sink responsible for:
1. Prevention of temperature
fluctuations that are outside the
range suitable for life.
2. Coastal areas having a mild
climate
3. A stable marine environment
Heat of Vaporization
• Water has a high heat of vaporization
• When you sweat, water pulls the heat away
from your body to cool you off
• The water actually contains some of the heat
Identify one property of water that is beneficial
to life on Earth and provide examples of how
this property is beneficial.
Universal Solvent
• Water is called the “universal solvent”
because it dissolves more substances than any
other liquid
• This means that wherever water goes, either
through the ground or through our bodies, it
takes along valuable chemicals, minerals, and
nutrients