1 PPTA PPT of the Year Runner-Up:

2 0 o C o C – Liquid Forms of Water < 0 o C - Ice > 100 o C - Vapor

3 Properties of Water Covalent bonding vs. Hydrogen bonding Covalent Bond - unequal sharing of electrons Hydrogen Bond – attraction of positive ends of molecules to negative ends of other molecules

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5 Water’s Properties Cohesion Adhesion Capillary Action Solvent High Specific Heat Solid water (ice) is less dense than liquid

6 Cohesion Water clings to polar molecules through hydrogen bonding – Cohesion refers to attraction to other water molecules.  responsible for surface tension  a measure of the force necessary to stretch or break the surface of a liquid

7 – Adhesion refers to attraction to other substances.  Water is adhesive to any substance with which it can form hydrogen bonds. Adhesion

8 Properties of Water Capillary Action Because water has both adhesive and cohesive properties, capillary action is present. Capillary Action = Water is attracted to some other material and then through cohesion, other water molecules move too as a result of the original adhesion. Ex: Think water soaking up a paper towel Ex: Water moves through plants this way

9 Solvent – fluid that dissolves solutes Solute – substance dissolved in a solvent to form a solution Example: Kool-Aid – water is the solvent and the flavoring and sugar the solutes Water is an effective solvent

10 High Specific Heat – High specific heat  Amount of heat that must be absorbed or expended to change the temperature of 1g of a substance 1 o C.  In other words, water can store a lot of thermal energy without actually increasing in temperature.

11 A large body of water can absorb a large amount of heat from the sun in daytime and during the summer, while warming only a few degrees. At night and during the winter, the warm water will warm cooler air. Therefore, ocean temperatures and coastal land areas have more stable temperatures than inland areas. The water that dominates the composition of biological organisms moderates changes in temperature better than if composed of a liquid with a lower specific heat. Impact of water’s high specific heat ranges from the level of the whole environment of Earth to that of individual organisms. The Earth is over 75% water!

12 Ice is less dense than water Density = mass/volume Water is less dense as a solid! This is because the hydrogen bonds are stable in ice – each molecule of water is bound to four of its neighbors. Solid – water molecules are bonded together – space between fixed Liquid – water molecules are constantly bonding and rebonding – space is always changing

13 Properties of Water So, can you name all of the properties of water? Cohesion Adhesion Capillary action Solvent Holds heat to regulate temperature (High specific heat) Less dense as a solid than a liquid