Biology Chapter 3 Notes

Biology Chapter 3 Notes - Chapter 3 Water and Life Overview...

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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 70–95% 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 Earth’s suitability for life Four of water’s 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 1°C
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Chapter 3 – Water and Life
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