Chapter 3 - Water and the Fitness of the Environment

Chapter 3 - Water and the Fitness of the Environment -...

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Chapter 3 Class Notes – Water and the Fitness of the Environment – Page 1 Max Sauberman AP Biology Class Notes Chapter 3 Water and the Fitness of the Environment Water on Earth: Clouds are made of water, in vapor form. Oceans are made of liquid water. The North and South Poles are made of ice (solid water). 60% of all humans are water. Approximately 70-95% of all cells are water. The Molecule That Supports All Life: Water is the biological medium of life on Earth. All living organisms require water more than any other substance. Earth is habitable because of the abundance of water. Polarity of Water: Polarity refers to opposite charges (+ or -) on opposite ends. Covalent bonding (the sharing of valence electrons) holds the H and O atoms together. H has one valence electron, and O has six, so when bonding to 2 H, O has 10 total electrons, 8 valence, so it is satisfied. The bond between the atoms is a polar covalent bond, because it involves an unequal sharing of electrons. Oxygen has greater electronegativity, so it develops a partial negative charge. (δ- denotes partial – charge). The hydrogen atoms hold partially positive charges (δ+). Electronegativity is the affinity for electrons… If an atom is electronegative, it wants electrons. Hydrogen Bonding: A hydrogen bond occurs in water between a δ+ hydrogen and a δ- oxygen of another water molecule, due to electrical attraction. Each water molecule can make a maximum of four hydrogen bonds, to bond with four other water molecules. This means that each oxygen atom can form hydrogen bonds with two hydrogen atoms.
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Chapter 3 - Water and the Fitness of the Environment -...

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