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Properties of Water. What is the importance of hydrogen bonding? How do compounds dissolve in water?. Hydrogen bonds in water. Water is polar The oxygen atom has a stronger attraction for electrons than hydrogen Oxygen pulls electrons closer – gains slight negative charge
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Properties of Water What is the importance of hydrogen bonding? How do compounds dissolve in water?
Hydrogen bonds in water • Water is polar • The oxygen atom has a stronger attraction for electrons than hydrogen • Oxygen pulls electrons closer – gains slight negative charge • Electrons are pulled away from hydrogen- slight positive charge -Balloon Demo
Hydrogen bonds in water • Opposite charges of polar molecules can interact to form hydrogen bonds
Properties Related to Hydrogen Bonds • Cohesion – water molecules bond to each other (Bonds to Itself) • Surface tension • Adhesion – water molecules stick to other polar molecules (Bonds to Other Things) • Capillary action (Yarn Tight Rope) • High specific heat – water resists a change in temperature (Stores Heat) (H20 vs Alcohol) • Less dense when it freezes • Most dense at 4oC
Water Acts as a Universal Solvent • Solute – substance that is being dissolved • Solvent – substance that dissolves another substance • Ionic and other polar compounds are broken apart by the slight charges on the water molecule
Acids and Bases • Acid – compound that releases H+ into solutions • Base – compound that removes H+ from solutions • A solutions H+ concentration is measured on the pH scale • Ranges from 0 to 14 • Acids – 0 to 6; H+ > OH- • Neutral – 7; H+ = OH- • Bases – 8 to 14; H+ < OH-
Acids and Bases • pH is regulated in organisms by substances called buffers • Buffers can remove H+ or add H+ to solutions to adjust pH • This maintains homeostasis • Human blood should be at a pH of 7.4, if it goes down to 7.0 or up to 7.8 then it is lethal