1. Water is Essential for Life
About 70% of the Earth is water
About 70% of your body is water
What makes water so important for life on Earth?

2. Demonstration How many drops of water do you think can fit on a penny?
Lets test it!!
Place penny on a flat surface
Use the pipette to place drops onto the penny
Count and record how many drops fit before water spills off the side of the penny

3. Demonstration How many drops of water actually fit on a penny?
How is this possible?

4. Properties of Water
Water has properties that make it essential to life:
Cohesion
Adhesion
High Surface Tension
Changes in Density at different temperatures
High Storage of Heat/Specific Heat
Universal Solvent

5. Cohesion is an attraction between substances of the same kind
Water molecules are attracted to other water molecules
Cohesion causes water to have a high surface tension

6. Adhesion is an attraction between substances of the different kinds
Water molecules are attracted to molecules other than water
Sometimes this can pull the water molecules against the force of gravity

7. Surface Tension
Surface Tension is caused by the attraction of the molecules and prevents the surface of the water from breaking
This is why you can see insects walking on the water’s surface

8. Changes in Density Water changes density at different temperatures.
This is why ice floats in your drinks and why ponds freeze at the top, leaving room at the bottom for fish and other life.

9. High Specific Heat
It takes a lot of energy to change the temperature of water
Allows the water to avoid drastic changes in temperature.
Good for your body
Good for ecosystems such as lakes and oceans.

10. Universal Solvent
Water dissolves more substances than any other liquid.

12. What Causes These Properties?
The weak Hydrogen Bonds present between the Oxygen of one water molecule and the Hydrogen of another

13. Review
The reason so many drops of water fit on a penny is because of two properties
Cohesion
High Surface Tension
These properties are caused by what?
Strong hydrogen bonds between the Oxygen of one molecule and the Hydrogen of another