KEY CONCEPT Water’s unique properties allow life to exist on Earth.

O Water is a polar covalent molecule. Polar molecules have slightly charged regions. O H _ +

Life depends on hydrogen bonds in water Hydrogen bonds form between + H atoms and – O2 atoms. Form between water molecules

surface tension (cohesion) less dense as a solid Adhesion high specific heat surface tension (cohesion) less dense as a solid Fig. The water's surface (left, dyed red) is curved down - water has greater adhesion. The surface of the mercury (right) is curved up - mercury has greater cohesion.

Examples of each property of water Adhesion - Attraction among molecules of different substances. Water will make H bonds with other surfaces like glass, soil or plants transpiration Ex: Adhesion helps plants transport water from roots to leaves -- water sticks to sides of stems and roots.

Adhesion Causes Capillary Action Capillary action - water molecules will “tow” each other along when in a tube or stem of plant. Which gives water the ability to “climb” structures

Examples of each property of water High specific heat – Water resists changes in temperature. Water also helps maintain homeostasis in cells by keeping temperatures stable. Fish in a pond is happy because the heat capacity of the water in his pond means temperature of the water will stay the same from day to night.

Examples of each property of water Cohesion - Attraction among water molecules. Water is “sticking” to other water molecules due to hydrogen bonds. Fig. Water’s surface tension comes from hydrogen bond’s that cause water molecules to stick together.

Examples of each property of water Surface Tension: a measure of the strength of water’s surface Nat Geo Basillisk Lizard-Video Fig. Water’s surface tension comes from hydrogen bond’s that cause water molecules to stick together.