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Unformatted text preview: Chapter 3 Water and Life Overview: The Molecule That Supports All of Life Water is the Biological medium on Earth- All living organisms require water more than any other substance Most cells are surrounded by Water , and cells themselves are about 7095% water The abundance of water is the main reason the Earth is habitable- Figure 3.1 Concept 3.1: Polar covalent bonds in water molecules result in hydrogen bonding The water molecule is a polar molecule : the opposite ends have opposite charges- Polarity allows water molecules to form hydrogen bonds with each other Figure 3.2 Concept 3.2: Four emergent properties of water contribute to Earths suitability for life Four of waters properties that facilitate an environment for life are- Cohesive behavior- Ability to moderate temperature- Expansion upon freezing- Versatility as a solvent Cohesion of Water Molecules Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion- Cohesion helps the transport of water against gravity in plants Adhesion is an attraction between different substances, for example, between water and plant cell walls- Figure 3.3 Surface tension is a measure of how hard it is to break the surface of a liquid- Surface tension is related to cohesion Figure 3.4 Moderation of Temperature by Water Water absorbs heat from warmer air and releases stored heat to cooler air- Water can absorb or release a large amount of heat with only a slight change in its own temperature Heat and Temperature Kinetic energy is the energy of motion- Heat is a measure of the total amount of kinetic energy due to molecular motion Temperature measures the intensity of heat due to the average kinetic energy of molecules The Celsius scale is a measure of temperature using Celsius degrees (C)- A Calorie is the amount of heat required to raise the temperature of 1 g of water by 1C Chapter 3 Water and Life The calories on food packages are actually...
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This note was uploaded on 10/04/2011 for the course BIOLOGY 1305 taught by Professor Adair during the Fall '09 term at Baylor.
- Fall '09