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?

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

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

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

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

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

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

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.

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.

Universal Solvent Water dissolves more substances than any other liquid.

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

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