Water: a special molecule Water is the most common molecule on Earth & in living organisms.Water is the most common molecule on Earth & in living organisms. Chemistry of living organisms takes place in water.Chemistry of living organisms takes place in water.

Structure of The Water Molecule H 2 0 is polar: it has a negative end and a positive end.H 2 0 is polar: it has a negative end and a positive end. –Oxygen is negative –Hydrogen is positive –Polarity makes water a good solvent. –Most things dissolve in water: sugars, salts, etc. –Water is called the universal solvent

Hydrogen Bonds Water molecules are attracted to each other.Water molecules are attracted to each other. (-) Oxygen is attracted to the (+) Hydrogen of another water molecule(-) Oxygen is attracted to the (+) Hydrogen of another water molecule The attraction is called a Hydrogen bond.The attraction is called a Hydrogen bond. Hydrogen bonds are very weak

Cohesion Cohesion: Molecules of the same type are attracted to each other.Cohesion: Molecules of the same type are attracted to each other. –Surface tension is a result of cohesion. Think: This water strider is more dense than the water. Why doesn't it sink?

Adhesion Adhesion: Molecules of different types are attracted to each other. Adhesion: Molecules of different types are attracted to each other. Plants move water up stems in part due to adhesion. Plants move water up stems in part due to adhesion. Water adhering to the sides of a test tube causes the meniscus

Capillary action Capillary action is the combination of cohesion and adhesion. This is the reason water can move up a paper towel against the force of gravity.

High heat capacity of water Heat capacity is the amount of energy it take to raise the temperature of a substance 1°C. Water must gain or lose a lot of energy for temperature to change. Result: a stable aquatic environment & the internal environment of cells.

Review Give an example, not used in this PowerPoint, of each of the special properties of water.