1. The Extraordinary Properties of Water

2. Water (1) threeWater is made up of three atoms: one oxygen and two hydrogen. The formula for a water molecule is H 2 O. H H O

3. Water is Polar (2-5) In water, the oxygen atom attracts more negative electrons Water is called a POLAR molecule –The oxygen end “acts” negative –The hydrogen end “acts” positive However, Water is neutral because it has an equal number of protons and electrons –Water has Zero Net Charge

4. Hydrogen Bonds Exist Between Water Molecules (6) Formed between a highly Electronegative atom of a polar molecule and a Hydrogen One hydrogen bond is weak, but many hydrogen bonds are strong

5. Interaction Between Water Molecules (7) A hydrogen bond is formed when the Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule

6. What are the Properties of Water?

7. Properties of Water (8,9,10) At sea level, pure water boils at 100 °C and freezes at 0 °C. The boiling temperature of water decreases at higher elevations (lower atmospheric pressure). For this reason, an egg will take longer to boil at higher altitudes

8. Properties of Water (11) CohesionCohesion AdhesionAdhesion High Specific HeatHigh Specific Heat High Heat of VaporizationHigh Heat of Vaporization Less Dense as a SolidLess Dense as a Solid

9. Cohesion (12-15) Is the attraction between particles of the same substance Cohesion produces surface tension when one water molecule attracts other water molecules –Surface tension is a measure of the strength of water’s surface Produces a surface film on water that allows insects to walk on the surface of water

10. Cohesion … Helps insects walk across water

11. Adhesion (16-20) It is attraction between two different substances.It is attraction between two different substances. –Water makes hydrogen bonds with other surfaces like glass, soil, plant tissues, and cotton Adhesion is water attracted to other materials while Cohesion is water attracted to itself. Adhesion produces capillary action as water is attracted to and pulled into a tube.Adhesion produces capillary action as water is attracted to and pulled into a tube. –Ex: transpiration is the process in which plants and trees remove water from the soil, and paper towels soak up water.

12. Adhesion Causes Capillary Action Which gives water the ability to “climb” structures

13. Adhesion Also Causes Water to … Form spheres & hold onto plant leaves Attach to a silken spider web

14. High Specific Heat (21,22) Is the amount of heat needed to raise or lower 1g of a substance by 1° C.Is the amount of heat needed to raise or lower 1g of a substance by 1° C. Water resists temperature change, both for heating and cooling.Water resists temperature change, both for heating and cooling. Water can absorb or release large amounts of heat energy with little change in actual temperature.Water can absorb or release large amounts of heat energy with little change in actual temperature.

15. High Heat of Vaporization (23-25) Is the amount of energy needed to convert 1g of a substance from a liquid to a gasIs the amount of energy needed to convert 1g of a substance from a liquid to a gas In order for water to evaporate, hydrogen bonds must be broken.In order for water to evaporate, hydrogen bonds must be broken. As water evaporates, it removes a lot of heat with it.As water evaporates, it removes a lot of heat with it.

16. High Heat of Vaporization (26,27) Water's heat of vaporization is 540 cal/g. In order for water to evaporate, each gram must absorb 540 calories of energy –This is why steam burns are much worse than hot water burns. As water evaporates, it takes a lot of heat and has a cooling effect. –but when it condenses, it releases heat to the skin.

17. Global Warming (28) Water vapor forms a kind of “blanket” which helps keep the Earth warm. –Heat from the sun that warms the surface of the earth is absorbed and held by the vapor.

18. Water is Less Dense as a Solid (29-31) Ice is less dense as a solid than as a liquid so ice floats Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances. Liquid water has hydrogen bonds that are constantly being broken and reformed.

19. Water is Less Dense as a Solid Which is ice and which is water?Which is ice and which is water?

20. Water is Less Dense as a Solid WaterIce

21. Homeostasis (32,33) Ability to maintain a steady state despite changing conditionsAbility to maintain a steady state despite changing conditions Water is important to this process because:Water is important to this process because: a. Makes a good insulator b. Resists temperature change c. Universal solvent-dissolves many substances d. Good coolant e. Ice protects against temperature extremes (insulates frozen lakes)