BSC Chapter Notes
BSC Chapter Notes BSC 114
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This 3 page Class Notes was uploaded by Rebecca Sharp on Sunday February 7, 2016. The Class Notes belongs to BSC 114 at University of Alabama - Tuscaloosa taught by Stevan Marcus in Winter 2016. Since its upload, it has received 31 views. For similar materials see Principles Of Biology I in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 02/07/16
All About Water! Water accounts for ¾ of the earth’s surface. All forms of life were aquatic for 3 billion years Water is considered the Biological Solvent; it’s the only one that occurs naturally in our Biosphere. Water is the only commonly, naturally occurring substance to exist in all 3 states in the natural environment Water has polar covalent bonds, with partially negative charged hydrogens and a partially positively charged oxygen. This is vitally important. This allows hydrogen bonds to form between other water molecules, which results in a phenomena called cohesion. o Cohesion; when a thing sticks to itself (like the sticky side of duct tape when it sticks to itself) o Adhesion; when a thing sticks to other things (like the sticky side of duct tape sticking to a wall) Water’s hydrogen bonds are 1/20 as strong as covalent bonds. This means they break and reform constantly, (each bond lasts about 3 trillions of a second) which allows water to be both adhesive and cohesive. Water forms a hydration shell around dissolved ionic compounds 4 Super Special Properties about water Water Molecule Cohesion; there are two really important things about the fact that water is cohesive. Water’s cohesive properties allow for enough surface tension to support small bugs walking across its surface, and it allows plants to transport nutrients against gravity. Trees suck water up their roots, and as the water evaporates off of the leaves, it pulls the chain of water molecules up, resulting in a vertical flow of water supporting the plant. This is also helped along by water’s adhesive properties, because the water molecules can ‘stick’ to the walls of the plant. Temperature Moderation by Water; water is a heat bank. It has a high specific heat of 1.0 calories/gram*C because of its hydrogen bonds. Heat must be absorbed to break the bonds and heat must be released when the bonds form. That means it takes forever to heat water up but also forever to cool it back down. This is important because it means the ocean keeps the coast line a little warmer in the winter and a little cooler in the summer time. It’s stable and it stabilizes the environment. The Floating of Ice on Liquid Water; this is so important. If ice sank, everything would freeze over and there would be no life on earth. In the summer only the top few inches of the ocean would thaw and the rest of all of the oceans would remain frozen solid. Life on earth only survived the last ice age because it was under an insulating layer of ice. That layer of ice protects the rest of the water from also being frozen into ice. This is because the hydrogen bonds in water expand when it freezes, which results in a density 10% less than water at 4*C (the densest water ever gets) Evaporative Cooling; this is mostly self explanatory. When the hottest bits of the water evaporates, what’s left is slightly cooler. What is not immediately apparent is why that’s so important. This is the main way that thermoregulation happens; this is how people and animals cool down, and the way bodies of water moderate heat. Dogs pant, and as the water evaporates off their tongues, they’re able to cool down. Humans sweat, and as the sweat, and as the sweat evaporates, our bodies are able to cool. A Quick Unit on Temperature and Heat Everything that moves has kinetic energy In relation to atoms, kinetic energy is thermal energy Thermal energy =/= Temperature. o Temperature is the average kinetic energy, without regard for the volume. o Thermal Energy is the total kinetic energy, and is highly concerned with volume Heat is the transfer of thermal energy One calorie, c, is the amount of energy required to heat 1 gram of water by 1 degree Celsius (or the amount of energy required to cool 1 gram of water by 1 degree Celsius) One Kilocalorie, C, is the amount of energy it takes to heat 1 kilogram of water 1 degree Celsius (or the amount of energy required to cool 1 kilogram of water 1 degree Celsius) One Joule equals .239 calories. One calorie equals 4.184 joules. And Water Dissolved Things Water can dissolve nonionic polar molecules and ionic compounds. Even proteins can dissolve in water, as long they’re polar enough for water to grab on to Hydrophobic substances have no affinity for water and cannot be dissolved by it. The oil family is hydrophobic, and so most cell membranes and structures are made out of oil related materials (oils have nonpolar covalent bonds) Hydrophilic substances have an affinity for water and thusly can be dissolved by it Molarity, Moles and Ms Molecular mass is the sum of all the protons and neutrons in a compound (the sum of all the masses of all the atoms in the compound) A Mole is 6.02E23 molecules. 6.02E23 daltons is a gram. Molarity is the number of moles of a given compound in a solution, this tells you the strength of the concentrate of the solution. The PH Scale Sometimes when hydrogen bonds are forming and breaking, one atom of H2O will steal a Hydrogen from another H2O, forming H3O (Hydronium) and OH (Hydroxide) Acids have a lot of hydronium and a little hydroxide. Bases have a lot of hydroxide and a little hydronium. Pure water is exactly in the middle of the scale. It’s a 7. Solutions with a higher number are basic, solutions with a lower number are acidic. Bleach, a basic compound, has a PH of 13. Battery Acid, an acidic compound, has a PH of 2.
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