Class Chapter 3 Lecture Presentation

Class Chapter 3 Lecture Presentation - Chapter 3 Water and...

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Biology Eighth Edition Neil Campbell and Jane Reece Chapter 3 Water and the Fitness of the Environment
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Learning Objectives: 1. To list and explain the properties of water that emerge as a result of its ability to form hydrogen bonds. These properties facilitate an environment for life on earth. 2. To learn how the structure of a water molecule allows it to interact with (different) molecules, and with other water molecules. 3. To distinguish between the following sets of terms: hydrophobic and hydrophilic substances; a solute, a solvent, and a solution. 4. To learn the definition of acid, base and pH, and how to solve pH problems.
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Overview: The Molecule That Supports All of Life Water is the biological medium on Earth. Three- quarters of the Earth’s surface is submerged in water. Water is the only common substance to exist in the natural environment in all three physical states of matter: solid, liquid and gas. All living organisms require water more than any other substance. Most cells are surrounded by water, and cells themselves are about 70–95% water. The abundance of water is the main reason the Earth is habitable.
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Overview: The Molecule That Supports All of Life What properties of the simple water molecule allow it to function as a support to all living organisims? Life as we know it could not exist without water. All the chemical reactions of life occur in aqueous solution. Water molecules are polar and are capable of forming hydrogen bonds with other polar or charged molecules. As a result, water has the following properties.
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Overview: The Molecule That Supports All of Life Water has the following properties. (1) Water molecules are cohesive; they form hydrogen bonds with each other. (2) Water molecules are adhesive; they form hydrogen bonds with polar surfaces. (3) Water is a liquid at normal physiological (or body) temperature. (4) Water has a high specific heat. (5) Water has a high heat of vaporization. (6) Water’s expansion at freezing.
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Water (H 2 O) Name and Molecular Formula Electron- distribution Diagram Lewis Dot Structure and Structural Formula Space- filling Model Covalent bonding in a water molecule
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The attraction of a particular kind of atom for the electrons of a covalent bond is called its electronegativity. The more electronegative an atom, the more strongly it pulls shared electrons toward itself. In a polar covalent bond , one atom is more electronegative than the other, and the atoms do not share the electrons equally. Unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule. Covalent Bonds and Electronegativity
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δ + δ + H H O H 2 O Because oxygen (O) is more electronegative than hydrogen (H), shared electrons are pulled more toward oxygen. Polar covalent bonds in a water molecule
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Class Chapter 3 Lecture Presentation - Chapter 3 Water and...

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