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

2. Life depends on hydrogen bonds in water.
Water is a polar molecule.
Polar molecules have slightly charged regions.
Nonpolar molecules do not have charged regions O H _ +
Atom: Oxygen
Charge: negative (-)
1. Weak Hydrogen bond 2. Explain: form between slightly positive and slightly negative atoms---break easily
Atom: Hydrogen
Charge: positive (+) O H _ + O H _ +

3. Properties of water related to hydrogen bonds:
1. Capillary action in plants….water moves up roots
2. Cohesion-water likes to bond with other water molecules (are cohesive or tight)
3. Adhesion-water will stick to or adhere to the sides of things

4. Many compounds dissolve in water.
A solution is formed when one substance dissolves in another.
Solvents dissolve other substances-usually water
Solutes dissolve in a solvent.
solution

5. Some compounds form acids or bases.
An acid releases a hydrogen ion when it dissolves in water.
high H+ concentration, taste sour…
pH = (1 is strongest acid, 6.9 is weakest)
more acidic
stomach acid pH between 1 and 3

6. A neutral solution has a pH of 7.
pure water pH 7

7. A base removes hydrogen ions from a solution.
low H+ concentration, taste bitter….are slippery
Called basic or alkaline
pH = (7.1 is weakest base, 14 is strongest)
bile pH between 8 and 9
more basic