1. Water Notes

2. C ompounds  Chemical bonds join atoms together in a stable form called a compound.  It is a substance made of two or more different elements. An example is Water.

3. Water Molecule  The molecular formula for water is H 2 O.  It consists of 2 Hydrogen atoms and 1 oxygen atom.

4. The Water Molecule  The oxygen and hydrogen atoms are covalently bonded to each other.  What does it mean to have a covalent bond? A chemical bond formed by the sharing of one or more electrons, especially pairs of electrons, between atoms.

5. Hydrogen bonding in water  Because of the polarity of the water molecule, neighboring water molecules are attracted to each other.  Remember, opposites attract  Water molecules can form weak bonds, or hydrogen bonds, with each other.  The hydrogen atom for one water molecule bonds weakly to the oxygen atom of another water molecule.

6. States of Water (remember back to I.S)  Solid, Liquid, Gas Solid  Liquid is called Melting Liquid  Solid Freezing Liquid  gas is called Evaporation Gas  Liquid is called Condensation Solid  Gas is called Sublimation

7. Storage of Energy  Organisms remove excess heat through water evaporation, while also maintaining heat with water. This allows organisms to maintain a constant internal temperature called homeostasis.

8. Property #1 Cohesion  Water is attracted to other water. The oxygen end of water has a negative charge The hydrogen end has a positive charge.  The hydrogen’s of one water molecule are attracted to the oxygen from other water molecules. This attractive force is what gives water its cohesive and adhesive properties Important: High surface tension = hard to break surface layer of water. Animals can use to stand, walk, run

9. Cohesion

10. Surface Tension  Surface tension is the name we give to the cohesion of water molecules at the surface of a body of water.  Water can support objects due to the Hydrogen bonding.

11. Surface Tension

12. Property #2 Adhesion 1. Clinging of one substance to another 2. Water clings to surface of vessels in plant. Overcomes gravity. 3. Cohesion keeps water molecules together moving upward

13. Adhesion

14. Capillary action in straws Water molecules are attracted to the straw molecules. One water molecule moves closer to the straw molecules then the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw. Capillary action is limited by gravity and the size of the straw. The thinner the straw or tube the higher up capillary action will pull the water Can you think of a real life example?

16. Property #3 Polarity  Water is a polar molecule, meaning that there is an unequal distribution of electrons.  Oxygen is partially negative, and hydrogen is partially positive.  This allows many substances to dissolve in water.  This quality allows water to be “the universal solvent”.

17. Polarity

18. #4 High Specific Heat 1. Requires high amount of heat (energy) to be absorbed/lost to change 1 g of water by 1 degree Celsius 2. Can absorb/release high amounts of heat 3. Moderates Earth’s climate-75% of Earth is water 4. Makes Earth habitable

19. #5 High Heat of Vaporization 1. Large amount of heat(energy) needed to change 1g of liquid water to gas 2. Hottest molecules lost (highest amt of energy), cooler ones left behind 3. Moderates climate. Warm air circulated to cold poles. 4. Evaporative cooling-plants and animals prevent overheating

20. #6 Solid Water Floats!  No other element in solid form floats in same liquid form – Unique to water 1. Water in sold form (ice) is less dense than liquid form (water) 2. Ice floats! 3. Lakes, ponds, oceans still habitable when top freezes – Ice insulates water

21. #7 Water is Neutral 1. pH value of 6-7.5 2. Not acidic or basic 3. Changes to the pH can damage or cause death to organisms, Ex. Acid rain 1. Your body has ways to deal with acidic/basic conditions – Buffers – neutralizes