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Published byJack Lang Modified over 9 years ago
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The Chemistry of Life Properties of Water
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The Water Molecule Polarity –Polar molecules have a region with a slight positive charge and a slight negative charge. –A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. Oxygen has 8 protons and a larger pull on the electrons than Hydrogen with just 1 proton.
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Hydrogen Bonds Polar water molecules act like magnets and attract each other Hydrogen Bonds –The attraction of the Hydrogen end (+) of one molecule for the Oxygen end (-) of another water molecule.
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Hydrogen Bonds
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Cohesion The attraction between molecules of the same substance (e.g. water). Allows some insects and spiders to walk on water.
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Adhesion Attraction between molecules of different substances Responsible for Capillary forces in plants
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Solutions & Suspensions Water is usually part of a mixture. There are two types of mixtures: –Solutions –Suspensions
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Solution Made of a solute and solvent. Ionic compounds disperse as ions in water (NaCl becomes Na+ Cl-) Evenly distributed SOLUTE –Substance that is being dissolved SOLVENT –Substance into which the solute dissolves
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Solution
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Suspensions Substances that don’t dissolve but separate into tiny pieces. Water keeps the pieces suspended so they don’t settle out.
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Acids, Bases & pH 1 water molecule in 550 million naturally dissociates into a Hydrogen Ion and a Hydroxide Ion Hydrondium Ion Hydroxide Ion Acid Base H 2 O H + + OH -
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The pH Scale Indicates the concentration of H + ions Ranges from 0 – 14 pH of 7 is neutral pH 0 – 6.99 is acid … H + pH 7.01 – 14 is basic… OH - Each pH unit represents a factor of 10 change in concentration
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Acids Strong Acid = pH 1-3 H + ions
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Bases Strong Base = pH 11 – 14 OH - ions
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Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH. Weak Acid Weak Base
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