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Biology 2 Chapter 3
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Polar Molecule Water molecules are shaped something like a wide V with opposite ends of the molecule having opposite charges
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Cohesion When the hydrogen bonds hold a substance together
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Adhesion The clinging of one substance to another
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Surface Tension A measure of how difficult it is to stretch or break the surface of a liquid.
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Kinetic Energy The energy of motion
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Heat A measure of the total amount of kinetic energy due to molecular motion in a body of matter How fast the molecules in an object move
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Temperature Measures the intensity of heat due to the average kinetic energy of the molecules
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Celsius scale The temperature scale most often used in science 0 degrees Celsius is freezing, 100 degrees Celsius is boiling
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calorie The amount of heat it takes to raise the temperature of 1 g of water by 1 degree Celsius
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Kilocalorie 1,000 calories, the quantity required to raise the temperature of 1 kilogram of water by 1 degree Celsius 1 kilocalorie = 4184 joules
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Specific heat The amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree Celsius High specific heatLow specific heat
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Heat of Vaporization The quantity of heat a liquid must absorb for 1 g of it to be converted to the gaseous state Water has a high heat of vaporization compared to other liquids To evaporate 1 g of water at 25 degrees Celsius about 580 cal of heat is needed
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Evaporative Cooling Occurs because the “hottest” molecules, those which have absorbed the greatest amount of kinetic energy are the most likely to leave a gas
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Solution A liquid that is a completely homogeneous mixture of two or more substances
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Solute and Solvent Solvent is the dissolving substance and the substance that is dissolved is the solute
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Aqueous Solution A solution in which water is the solvent
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Hydration Shell The sphere of water molecules around each dissolved ion
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Hydrophilic Any substance that has an affinity for water Hydro = water, philic = loving Like cotton and other forms of cellulose
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Colloid A stable suspension of fine particles in a liquid
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Hydrophobic Substances that are nonionic and nonpolar which actually seem to repel water E.g.- oil
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Molecular Mass The sum of the masses of all the atoms in a molecule
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Mole 6.02 x 10 to the 23 rd power Avogadro’s number The molecular mass in grams is a mole
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Molarity The number of moles of solute per liter of solution The unit of concentration most often used by biologists for aqueous solutions
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Hydrogen Ion H+, a single proton with a charge of 1+
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Hydroxide Ion OH-, has a charge of 1-
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Acid A substance that increases the hydrogen ion concentration of a solution
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Base A substance that reduces the hydrogen ion concentration of a solution
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pH A scale which measures the acidity or alkalinity of a substance The lower the pH the more acidic a substance is The higher the pH the more basic a substance is Note that each decrease in pH by one pH unit means a tenfold increase in the concentration of hydrogen ions.
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Buffers Substances that minimize changes in the concentrations of H+ and OH- in a solutions
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Acid precipitation Refers to rain, snow or fog with a pH lower or more acidic than pH 5.6
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