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AP Biology (61-85)

Terms in this set (35)

Energy is _____ when bonds form, and energy is _____ to break bonds
Energy is released
Energy is required
Explain how bodies of water act as "heat sinks" or "heat sources"
Lake Michigan in the summer is the heat sink
When two bodies of matter are in contact, collisions occur and heat Energy is trasnferred from the warmer to cooler body, until both are the same temperature
As the lake cools down, hydrogen bonds form and release energy
Vaporization/Evaporization
Transformation from a liquid to a gas.
Vaporization occurs when a molecule moves fast enough to overcome the attraction of other molecules in the liquid.
Heating a liquid increases the average kinetic energy and increases the rate of evaporation.
Heat of Vaporization
The quanity of heat a liquid must absorb for one gram of it to be converted from the liquid to the gaseous state
What is water's heat of vaporization? (calories per gram)
580 calories per gram
Why does water have a high heat of vaporization?
All hydrogen bonds must be broken before transofrmation can occur
Effect of water's high heat of vaporization in moderating the Earth's climate
Stabalizes temperature in organisms and bodies of water. Prevents overheating.
Ex) a large amount of solar heat is absorbed by tropicaseas and consumed during the evaporation of surface water. As moist tropical air moves to the poles, water vapor condenses to form rain, releasing heat.
Evaporative Cooling
As a liquid evaporates, the surface of the liquid that remains behind cools down. This occurs because the hottest molecules, those with the greatest KE are the ones most likely to leave as gas
How evaporative cooling helps keeps bodies of water, leaves of plants, and humans from overheating
-Evaporation of water from leaves of a plant helps keeo the tissues in the leaves from becoming too warm from sunlight
-Evaporation of sweat from human skin dissipates body heat and helps prevent overheating
Why is ice less dense than water?
At 0 degrees Celsius, water begins to freeze because its molecules begin to move too slowly to break hydrogen bonds.
See picture
Why is water being less dense as a solid rather than a liquid essential to life?
As ice thickens it forms hydrogen bonds which release energy to water below it.
Ice is less dense that water so it can float in water, therefore allowing life to occur underneath a frozen layer during cold months
The floating ice insulates the liquid water
What temperature is water the most dense at
4 degrees Celsius
Solutions, Solute, Solvent
A liquid that is completely homogeneous mixture of two or more substances is called a solution.
The dissolving agent of a solution is the solvent
What is being dissolved is the solute
Aqeuos Solution
Water is the solvent
How does water dissolve NaCl (Ionic Compound)
Slightly negatively charged oxygen regions of water are attracted to Sodium cations. The hydrogen regions are slightly positive and are attracted to chloride anions. As a result water molecules surround the individual sodium and chloride ions, seperating and shieleding them from one another.
Hydration Shell
The spehere of water molecules around each dissolved Ion (i.e. Na and Cl) is called a hydration shell.
Working inward from the surface of each salt crystal, water eventually dissolves all ions.
Bound Waters
A shell of water stuck to an ion
Hydropholic
Any substance that has an affinity for water
Cotton which is hydropholic does not dissolve in water
Hydrophobic
Any substance that does not have an affinity for water and are nonionic or nonpolar
Ex) Oil which has mostly non-polar bonds
Mole
6.02x 10^23 = 1 dalton= I gram
Hydrogen Ion
When a hydrogen atom participates in a hydrogen bond between two water molecules it can shift from one molecule to another, the hydrogen atom leaves an electron behind. What is actually transferred is a hydrogen ion.
=Hydronium Ion H30 (H+ does not exist often or long)
Hydroxide Ion
OH-
The water molecule that has lost a proton
Almost never exists in life because it is poisinous
Acid/Base
Base is anything that removes H+ ions from a solution
Acid is anything that increases H+ concentration
Why is water an excellent solvent?
Water is a versatile solvent due to its polarity which it allows it to form hydrogen bonds more easily. &+ end bonds with anions &- end bonds with cations
Amphipathic Molecule
Polar end and Non-Polar end
Ex) Soaps and Phosholipids
How does Soap work? ***
Soap is an ampipathic molecule
Polar end will bond with water and nonpolar end can bond with grease.
When water is removed so will the bonds formed with nonpolar grease
pH is a log scale. What does that mean?
For every 1 change in pH it is a ten fold change (10 times than 100 times then 1000, etc..)
pH of human blood
7.2
pH of cytoplasm (fluid within cells)
6.8
pH of Hydrochloric Acid (HCL) in stomach
1-2
Stomach Acid and how that works
Stomach is a modified external enviornment. Mucin (protein) is dissolved in water and form mucus. A thick layer of mucus coats our stomach so acid never touces it. Stomach acid is neutralized because the pancreas creates a basic solution before it reaches the small intestine
Advantage of Stomach Acid
acid dissolves metal. Calcium and Phosphoros are metals (make bones strong). Prevents digestive track from being punctured.
Buffers
substances that help resist change in pH. To be a buffer you must be able to act as either an acid or a base
Bicarbonate Acid
(HOC3 -)
Acidification of the oceans by atmospheric acid (CO2) and its effects on marine life
Burning fossil fuels releases CO2. It is partiall absorbed by the ocean causing the water to become more acidic (forming carbonic acid).
Ocean acidification causes the carbonate ion concentration to decrease. Carbonate ions are required for calcification, production of CaCo3 + reef and building shells.
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