1. Properties of Water

2. 1. Is the Universal Solvent
It can dissolve many substances, like nutrients and wastes.
Negative ion attracts positive pole of water
Positive ion attracts negative pole of water

3. 2. Water has polarity
This means that one side of the molecule is positive, one side is negative.

4. 3. Water has Polar Covalent Bonds-
Negative Pole
Covalent Bond
Covalent Bond O H H + +
Positive Pole
Shared electrons (which are negative) spend more time around the O (oxygen).
This makes the O side of water slightly (-) and H’s slightly (+).

5. **Draw this in your notes**
4. One water molecule is attracted to other water molecules by hydrogen bonds. + + -
Hydrogen Bonds + - + -
**Draw this in your notes** + + - + + + - +

6. Water’s Polarity and its Ability to Form Hydrogen Bonds:
gives water unique properties which make water very important on Earth

7. Since water is polar and can form hydrogen bonds:
a. Water molecules are attracted to other water molecules by
COHESION – the attraction between molecules of the same substance
b. Water molecules are attracted to other polar molecules by
ADHESION – the attraction between molecules of different substances

8. 5. Exhibits Surface Tension
Water molecules stick together (cohesion) on surface of water
This allows the water strider to walk on water.

9. 6. Capillary Action Water can climb thin tubes.
Water is able to climb from roots all the way up to leaves at the top of a tree
Adhesion to the roots
Cohesion to neighboring water molecules, pulling them along.

10. 7. Resistance to Changes of Temperature
Water can absorb a lot of heat without getting hot, and can lose a lot of heat without getting cold.

11. Resistance to temperature change
allows organisms to maintain constant body temperature, AND keeps the Earth at a fairly constant temperature.
Remember – about 2/3 of Earth is covered with water, and up to 60% of a human’s weight is water!

12. 8. High Heat of Vaporization
It takes a lot of heat energy to change liquid water to water vapor, because hydrogen bonds must be broken.
Evaporation of sweat takes heat energy from the body, allowing sweat to cool us.

13. 9. Expands as it freezes
Hydrogen bonds lock into place, and push water molecules farther apart.
Ice is less dense than water

14. Low Density- Importance of Expansion upon Freezing
Ice Floats!
Life at the bottom of lakes does not get crushed
Ice also serves as an insulator
Ice breaks rocks into soil

15. So why is water so important?
Almost every solution is made of water.
Acids and bases are made of water
We are mostly water.