1. Quick Review: Water is Wonderful!

2. Water
H2O : one oxygen and two hydrogen. 1

3. Hydrogen Bonds
-formed between an atom of a polar molecule and a Hydrogen
(polar means that it has a charge – one part is negative, one part is positive)
-one hydrogen bond is weak, but many hydrogen bonds are strong

4. H bonds result in surface tension due to the cohesion of water (it sticks to itself)10

5. Water also has adhesion
- it will make H bonds with other surfaces such as glass, soil, plant tissues, cotton… etc.
i.e. transpiration process which plants and trees remove water from the soil, and paper towels soak up water.
Capillary action-water molecules will “tow” each other along when in a thin glass tube. 1

6. Which is ice and which is water?1

7. H bonds hold molecules in place
Water
H bonds constantly
break / form
Ice
H bonds hold molecules in place 1

8. Water is Less Dense as a Solid

9. H bonds need to break / reform = energy needed!
Water resists temperature change, both for heating and cooling (it has high specific heat)
An Example…
Saskatoon
Winter -20 C
Summer 35 C
Vancouver
Winter 5 C
Summer 20 C
Why?
H bonds need to break / reform = energy needed!

10. Homeostasis
Ability to maintain a steady state despite changing conditions
So why is water important to us?
Resists temperature change
(acts as both coolant and insulator)
-Universal solvent for chemical reactions
- Lubricant 4