1. Essential for Life

2. 3.1.1 The most frequently occurring chemical elements in living things are: Carbon Hydrogen Oxygen Nitrogen

3. 3.1.2 A variety of other elements are needed by living organisms, including: ElementRole in living organisms SulfurFound in some amino acids CalciumCo-factor in some enzymes, found in bones of animals PhosphorusPhosphate groups in ATP IronIn cytochromes, & in hemoglobin in animals SodiumIn membrane function, & sending nerve impulse in animals

4. Water is a polar molecule

5. Water’s Polarity… … allows for Hydrogen Bond formation between water molecules

6. Properties of Water 1. Thermal – good temperature regulator 2. Cohesive – likes to stick to each other 3. Solvent – molecules like to dissolve in water

7. Thermal Properties High Specific Heat Water can absorb and give off a lot of heat without changing temperature very much. Why is this important for living things? Temperature stabilizer High Heat of Vaporization When water evaporates, it absorbs a lot of heat. Why is this important for living things? Sweating (the evaporation of water) removes heat from your body.

8. Sweat! It really does cool you off.

9. Cohesive Properties Cohesion: when molecules of the same type are attracted to each other. What is the attraction from?? Hydrogen bonding… How do we see this? Water forms droplets if spilled Water has surface tension Water moves up the vascular tissue of plants – great for transporting nutrients with it!

10. Water Strider……Paper clip

11. Solvent Properties Water dissolves polar molecules. Most molecules found inside and outside most cells are polar molecules… Examples – Carbohydrates, proteins, DNA Is the medium in which metabolic reactions take place

12. ICE When most molecules become cold, they get closer together. When water molecules become cold, they move apart, eventually forming ice. Ice is then less dense than water. This means ice floats! Why is this important for life on earth? Floating ice insulates water below it

13. Ice floats!

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