The Properties of Water

1. Properties of Water
Learning Goals
• You will be able to describe the
structure of water.
• You will be able to identify the
properties of water.
• You will be able to describe how
these properties of water are
essential for sustaining life on
Earth.

2. Water’s Structure
• Water is a molecule made of two hydrogen
atoms and one oxygen atom
• The Hydrogen atoms have a slightly
positive charge and the Oxygen atoms
have a slightly negative charge

3. Polarity
• Polar Molecule= a
molecule that has
one side that is
more negative
than the other.
• The Oxygen atom
is more negative
than the
Hydrogen atoms

4. 1. Think about the
following…
What are the atoms
that make up a water
molecule?
Which type of bonds
hold the atoms
together?
What does polarity
mean?
2. Post your thoughts in
Today’s Meet.
Press Pause, Think, & Share

5. What did you discuss?
• What are the atoms that make up a water molecule
• 1 Oxygen atom and 2 Hydrogen atoms
• Which type of bonds hold the atoms together
• Covalent bond because the atoms share
electrons
• What does polarity mean?
• Polar Molecule= a molecule that has one side
that is more negative than the other.

6. • Polar molecule
• Cohesion and Adhesion
• High specific heat
• Density – greatest at 4oC (AKA water
floats)
• Universal solvent
• Neutral pH
Properties of Water

7. • Water has a variety of unusual properties
because of attractions between these polar
molecules.
– The slightly negative regions of one molecule are
attracted to the slightly positive regions of nearby
molecules, forming a hydrogen bond.
– Each water molecule
can form hydrogen
bonds with up to
four neighbors.

8. HYDROGEN BONDS
• Hold water molecules
together
• The hydrogen bonds
joining water molecules
are weak, about 1/20th as
strong as covalent bonds.
• They form, break, and
reform with great
frequency
• Extraordinary Properties that
are a result of hydrogen
bonds.
– Cohesive behavior
– Resists changes in
temperature
– High heat of vaporization
– Expands when it freezes
– Versatile solvent

9. Organisms Depend on Cohesion
• Cohesion is responsible for the
transport of the water column in
plants
Why is this important?
• Cohesion among water molecules
plays a key role in the transport of
water against gravity in plants
• Adhesion, clinging
of one substance to
another, contributes
too, as water adheres
to the wall of the
vessels.
Hydrogen bonds hold the substance
together, a phenomenon called cohesion

10. • Surface tension, a measure of the force
necessary to stretch or break the surface of a
liquid, is related to cohesion.
– Water has a greater surface tension than most
other liquids because hydrogen bonds among
surface water molecules resist stretching or
breaking the surface.
– Some animals can stand,
walk, or run on water
without breaking the
surface.

11. Moderate Temperatures on Earth
• Temperature is the measurement of the
movement of atoms/molecules.
• As water temperatures increase,
hydrogen bonds begin to break.
• As water temperatures cool, hydrogen
bonds from more readily.

12. Why is this important?
1. Prevention of temperature
changes that are outside the
range suitable for life.
2. Coastal areas having a mild
climate
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.

13. Evaporative Cooling
• The cooling of a surface
occurs when the liquid
evaporates
• This is responsible for:
– Moderating earth’s
climate
– Stabilizes
temperature in
aquatic ecosystems
– Preventing
organisms from
overheating

14. Density of Water
• Most dense at 4oC
• Contracts until 4oC
• Expands from 4oC to
0oC
Why is this important?
1. Prevents lakes from totally freezing so aquatic
organisms can live
2. Ice forms on the surface first—the freezing of the
water releases heat to the water below creating
insulation.
3. Acts as hunting grounds for some organisms

15. Universal Solvent
• Because of water’s
polarity many
compounds dissolve
in water
Why is this important
• Most biochemical
reactions involve
solutes dissolved in
water- we need to
get stuff in our cells!

16. Neutral pH
• pH Scale
– Measures the degree
of acidity (0 – 14)
• Water has a pH
around 7
Why is this important?
• Most biological
functions take place
in a neutral pH

17. 1. Think about the
following…
Name as many
properties of
water as you can
(Hint:There are 6)
2. Post your thoughts
in Today’s Meet
Press Pause, Think, & Share

18. What did you discuss?
• What are the properties of water?
– Polar molecule
– Cohesion and Adhesion
– High specific heat
– Density – greatest at 4oC
– Universal solvent
– Neutral pH

19. • In OneNote make a table that has one
column with the properties of water and
another with why these properties are
important. Fill the table in with what you
know.
Properties of Water Why these properties are important
to life