1. 2.2 Properties of Water
Biology A and C

2. Water’s unique properties allow life to exist on Earth
Have you ever thought about why you need water to survive?
Your cells and the cells of every living thing on the planet are mostly water.
Why?

3. Properties of Water Water gives cells structure
Water transports vital materials to and from organs in the body
All of the processes of life take place in the watery liquid in the body
Water’s unique properties and cellular structure are important for living things.

4. Properties of Water
How do fish survive a cold winter if their pond freezes?

5. Properties of Water
Because ice floats and covers the water’s surface, leaving the liquid underneath
The ice acts as an insulator .
Water expands when it freezes (That means it gets bigger)
This is different from most liquids

6. Water Molecules
Water is a polar molecule – because the hydrogen molecules are on opposite ends of the oxygen molecule (H2O)
Oxygen is the nucleus (8 protons)
Hydrogen (1 proton)
Oxygen has a stronger pull
Hydrogen gains small positive charges

7. Water Molecules
The opposite charge of polar molecules interact to form hydrogen bonds
A hydrogen bond is an attraction between a slightly positive hydrogen atom and a slightly negative atom, often oxygen or nitrogen.
Water has a hydrogen bond
Other liquids do too
Hydrogen bonds are part of the structures of proteins and of DNA.

8. Water Molecules

9. Water Molecules
Water has a strong bond in the molecule – this bond is the hydrogen bond
With out this bond, water would act differently…
Water would boil at a lower temperature
Water would freeze at a higher temperature

10. Water Molecules
High Specific Heat: Water resists changes in temperature
Cohesion: Water sticks together (creates surface tension), such as when bugs land on water, or water beads up on a newly washed car
Adhesion: Water sticks to things. Such as inside a test tube, a water bottle, or the way water can be transported from the roots of plants to leaves.

11. Water and its properties
Most other liquids dissolve in water…
Ice tea mix
Kool aid
Coffee
Sugar
Salt
What else can you think of?

12. Water Properties
When these things dissolve in water, we call it a solution
Solvent – the substance that is the greater amount and that dissolves another substance (like water)
Solute – is the item that gets dissolved (like Kool Aid)

13. Water Properties
The reason many things will dissolve in water is because they are also polar molecules (things like sugar and proteins)
Therefore, there is an attraction between the molecules

14. Water Properties Now, think about fats and oils.
Do they dissolve easily in water?
Why?
Oils are nonpolar molecules