Water
Water Facts
● There is the same amount of water on Earth as
there was when the Earth was formed. The
water from your faucet could contain molecules
that dinosaurs drank.
● Nearly 97% of the world’s water is salty or
otherwise undrinkable. Another 2% is locked in
ice caps and glaciers. That leaves just 1% for all
of humanity’s needs — all its agricultural,
residential, manufacturing, community, and
personal needs.http://water.epa.gov/learn/kids/drinkingwater/waterfactsoflife.cfm
● Water regulates the Earth’s temperature. It also
regulates the temperature of the human body,
carries nutrients and oxygen to cells, cushions
joints, protects organs and tissues, and removes
wastes.
● 75% of the human brain is water and 75% of a
living tree is water.
● A person can live about a month without food,
but only about a week without water.
● Water expands by 9% when it freezes. Frozen
water (ice) is lighter than water, which is why
http://water.epa.gov/learn/kids/drinkingwater/waterfactsoflife.cfm
Water
• Water is a compound
• Formula
– H2O (2 Hydrogen and 1 Oxygen)
Why is water unique?
• Hydrogen Bonds-Polarity, High Specific heat,
cohesion, adhesion
Polarity
• Polarity allows water to be the perfect
solvent
– Water can dissolve many things
– No other liquid can come close to being able
to dissolve as many thing as water can
– Because of this, water is nearly always
carrying something else along with it
Hydrogen bonds
• High specific heat- resists changes in
temperature
• Cohesion- water sticks to itself causing
surface tension
• Adhesion- water sticks to other things,
meniscus, capillary action
• Capillarity- water travels upward through
small tubes due to adhesion and cohesion
Other Special Qualities
• Water is the only naturally occurring
compound on Earth that can be found in
all three physical states
• When water freezes it floats
– Extremely unique property
– Contracts as it cools until it hits 4° C when it
expands again
Why does Water Expand into Ice?
Diffusion
• Diffusion-The movement of particles from
areas of high concentration to areas of
low concentration
• Examples
– Perfume bottle
– Cookies in the oven
– Kool-Aid
What diffusion looks like
•http://highered.mcgraw-
hill.com/sites/0072495855/student_view0/c
hapter2/http://highered.mcgrawhill.com/sites/0072495855/student_view0/c
hapter2/animation__how_diffusion_works.ht
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Solutions
• Mixture- a blend of substances that is not
equal throughout (heterogeneous)
• Solvent + Solute = Solution
• Solvent- Liquid capable of dissolving other
substances
• Solute- substance being dissolved
• Solution- a mixture of substances that is
equal throughout (homogeneous)
Mixtures
Solutions
+
Solvent
=
Solute
Solution
Osmosis
• Osmosis-Diffusion of water molecules, usually
•
•
•
involving a semi-permeable membrane
Concentration Gradient- difference in
concentration from one side of membrane to the
other
Equilibrium-the same everywhere
Remember water always moves from areas of
high water concentration to areas of low water
concentration
Osmosis
http://highered.mcgrawhill.com/sites/0072495855/student_view
0/chapter2/animation__how_osmosis_w
The tonics of life
• Isotonic-Concentration of solutes is the
same in solution and cell.
• Hypertonic-Concentration of solutes is
higher in the solution.
• Hypotonic-Concentration of solutes is
lower in the solution.