Water, pH notes Properties of water 1. polarity 2. cohesion 3. adhesion 4. stable temp. 5. expands when freezes Acids, bases A. pH 1. acid 2. base 3. neutral B. Buffers III. Organic

Summary Section 2 – pages 152-156 Water and Its Importance Water is—The most important compound in living organisms Water—makes up 70- 95 % of most organisms. Ex. Blood and sap are mostly water Summary Section 2 – pages 152-156

Unique Qualities of Water 1. Polarity: uneven distribution of electrons between the oxygen and hydrogen atoms, oxygen is -, hydrogen is +

2. Cohesion Water attracted to other water molecules Water molecules act like stretched film on water surface Water beads up on waxy leaf, no attraction to leaf Also called surface tension

3. Adhesion Water creeps up thin tubes because of attraction to other substances Allows plants to get water from roots to leaves Also called capillary action

4. Water resists temperature changes Requires a lot of heat to increase water temperature Helps cells to have a constant temperature

Summary Section 2 – pages 152-156 5. Water expands when it freezes Very unique to water Summary Section 2 – pages 152-156 Ice takes up more volume than water Ice is less dense than water so it floats

Acids, Bases, and pH pH—a measure of how acidic basic or solution is, scale ranges from 0-14 Acid--substance with pH below 7, forms hydrogen (H+) ions in water Base—substance with pH higher than 7, forms hydroxide (OH-) ions in water

Neutral: solution with pH = 7, concentration of H+ ions and OH- ions are equal

Which is a stronger acid, pH 2 or pH5? Which is a stronger base, pH 8 or pH 12?

Examples If dissolved in water, will these compounds be acidic, basic, or neutral? 1. C9H8O4 2. Mg (OH)2 3. Ca CO3

Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH Help maintain homeostasis

Organic Derived from something living or once living Contains carbon (exception: carbon dioxide) Are the following organic or inorganic? C6H12O6 H2O CH4 CO2