1. Water
The Magic Molecule…..

2. Properties of Water
Water is one of the most unique substances found in the universe and all of life depends on it.
A simple molecule formed by the sharing of electrons (covalent bond) between one oxygen and two hydrogen

3. Water is a polar molecule...
Oxygen attracts the shared e- in H2O much more strongly than does H, so the shared e- are closer to the O atom than to the H atoms.
This makes the H slightly positive and the O slightly negative. (Technically still neutral, p+=e-)
Thus, the H in water is attracted to the O of other water molecules and vice versa.
This type of bond is called a hydrogen bond, one of the weakest bond types, but very important!

4. Physical Properties:
Water is called the "universal solvent" because it dissolves more substances than any other liquid. This means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

5. Water is neutral on the pH scale.
Pure water has a neutral pH of 7, which is neither acidic nor basic.
Rain has a naturally acidic pH of about 5.6 because it contains natural derived carbon dioxide and sulfur dioxide.

6. All 3 states are common!
Water is unique in that it is the only natural substance that is found in all three states -- liquid, solid (ice), and gas (steam) -- at the temperatures normally found on Earth.

7. Water is unusual in that the solid form, ice, is less dense than the liquid form, which is why ice floats.
When water is frozen its molecules arrange themselves in a particular highly organized rigid geometric pattern that causes the mass of water to expand and to decrease in density.

8. Water freezes from the outside to the inside
Water freezes from the outside to the inside. This creates a barrier between the harsh environment and the water underneath.
How would this be good for life in rivers, ponds and streams?
What would happen if it froze from the inside out?

9. Water has a high specific heat.
Specific heat is the amount of energy required to change the temperature of a substance.
Because water has a high specific heat, it can absorb large amounts of heat energy before it begins to get hot.
It also means that water releases heat energy slowly when situations cause it to cool.
Water's high specific heat allows for the moderation of the Earth's climate and helps organisms regulate their body temperature more effectively.

10. Water has a high specific heat index
Water has a high specific heat index. This means that water can absorb a lot of heat before it begins to get hot.
Why is water is valuable to industries and in your car's radiator as a coolant.

11. A Question...
Explain why the temperature change between seasons is gradual rather than sudden, especially near the oceans

12. Hydrogen bonds only last a few trillionths of a second, yet at any instance most of the water molecules are bonded to other.
The tendency to stick together is called cohesion.

13. Surface tension
Surface tension is a measure of the strength of the water's surface film. The attraction between the water molecules creates a strong film, which among other common liquids is only surpassed by that of mercury.

14. More on surface tension...
Surface tension is essential for the transfer of energy from wind to water to create waves. Waves are necessary for rapid oxygen diffusion in lakes and seas.

15. Capillary Action Also called capillarity
What are some other examples of where this occurs?

16. Capillary Action Surface tension is responsible for capillary action.
May be defined as the ability of a liquid to climb up a surface against the pull of gravity

17. Capillary Action
For example, in a thin glass tube, when the molecules at the edge adhere to the molecules of glass just above them, they (at the same) time pull other water molecules along with them.
The water pulls the entire body of water to a new level causing
the liquid to rise
because the water is in
contact with the solid.

18. Thus water readily wets many materials
Thus water readily wets many materials. (Capillary action allows a paper towel or a sponge to be used to soak up spilled water.) Without this property, the nutrients needed by plants and trees would remain in the soil.

19. Water Cycle

20. OK then, Water..The Magic Molecule
What are the properties that make it so unique?
Can you DESCRIBE 6?
Could you explain them in paragraph form?