AP Biology Chapter 3 Notes PDF

Preview

Summary

Notes for AP biology chapter 3...

Description

Chapter 3 Notes: Water and Life 3.1 Polar Covalent Bonds in Water Molecules Results in Hydrogen Bonding ● ● ● ● ●

Polar Covalent Bonds- Shaped like a “V”; has two hydrogen atoms joined together by an oxygen atom by single covalent bond. Oxygen is more electronegative than hydrogen; the electrons spend more time with oxygen rather hydrogen (covalent bond) Electronegativity- The attraction of a particular atom for the electron of a covalent bond. (Basic Def.= Element whose uncharge atoms add electrons to become anion= negative) Polar Molecule- The unequal sharing of electrons and water’s “V”-like shape, making it overcharge and not distributed properly Oxygen Region= partial NEGATIVE (-) charge; Hydrogen Region= partial POSITIVE (+) charge

3.2 Four Emergent Properties of Water Contribute to Earth’s Suitability for Life Cohesion- How water is attracted to the SAME molecule; H-bonding Adhesion- The attraction between two different substances Surface Tension- Measuring of how difficult to stretch or break the surface of any liquid Ex. Some small animals, such as spiders, are able to stand, walk, and even run across the water without breaking the surface ● Water has a greater surface tension than most liquids -Due to water and air in an order arrangement of water molecules, H-bonding to one another and to the water below ● When water is a liquid H-bonding is very fragile ● H-bonding breaks often, constantly finding new partners -Large % of the H2O molecules are bound together by H-bonding SUMMARY!! H2O: It’s held together by polar covalent bonds (STRONG) H2O Molecules: Held together by H-bonding “WEAK” ● ● ●

★ Moderation of Temperature by Water Heat and Temperature ● Kinetic Energy- Anything that moves; faster an object moves greater the kinetic energy ● Temperature- The measure of heat intensity that represents the average kinetic energy of the molecules, regardless of volume ● Heat is a form of energy, therefore heat depends (in part) on the volume -When two objects come together different temperatures come together, heat passes from the warmer to the cooler object until the two are the same temperature...molecules in the cooler object speed up Ex. When a student sits in a seat for a long time and the seat is cool before he/she sits down, and after when the student leaves the heat for that person’s body transfers to the chair and makes the cool molecules in the chair speedup and contact the heat.

●

H2O absorbs heat from the air that is warmer and releases it to the air that is cooler, therefore H2O is a heat breaker as it can collect and release large amounts of heat with the slightest change in its own temperature Ex. A larger swimming pool will conduct more heat, if left in the sun. due to the smaller volume rather than a larger swimming pool to the greater amount of volume in the pool that is being taken up. ★ Water’s High Specific Heat ● Specific Heat- The amount of heat that must be absorbed or last for 1g of that substance to change its temperature by 1 degree Celsius; therefore the specific heat of H2O= 1cal/g(degree)Celsius ● H2O specific heat is relatively high compared to other substances; due to H-bonding -Cause of such a high specific heat, H2O changes it temp. when it absorbs or loses a given amount of heat ● Specific heat can be thought of as a measure of how well a substance can resists changing its temp. when absorbing heat ● On Earth, H2O’s specific heat helps decrease drastic temp. change; At night and in the winter the gradual cooling of H2O warms the air, therefore coastal areas ● High specific heat of H2O tends to stabilize each temperatures circulation for evolution of marine life ★ Evaporative Cooling ● Evaporative Cooling- A change of a liquid to a gas -If molecules move fast enough, they escape and become a gas ● Even at low temp. evaporation occurs -Increase heat ----> increase kinetic energy ----> increase speed of gas -Evaporative Cooling helps stabilize temps. in lakes and ponds, and allows animals on land to prevent overheating ● Heat of Vaporization- Quality of heat a liquid must absorb for 1g to change to a gas ● H2O has a HIGH heat of vaporization relative to other liquids...to evaporate 1g of H2O at 25 degrees Celsius approximately 580 cal. of heat approximately 2x’s greater than a gram of alcohol ● High heat of vaporization due to the strength of H-BONDS!!!! -This helps moderate temp. on Earth ● Much cooler heat absorbed by tropical seas are consumed during the evaporation of surface water...then as moist tropical air circulates toward the poles, it releases heat, condenses and forms rain ● As liquid evaporates, surface of liquid remaining, cook down AKA “Evaporative Cooling” because “Hottest” molecules are most likely to leave as a gas ★ Floating Ice on Liquid Water ● Ice is less dense than liquid water ● Most materials contact when it becomes denser after being solidify....water expands 3.3 Acidic and Basic Conditions Affect Living Organisms

● ●

Hydrogen Ion (H+)- A single proton with a charge of 1+ Hydroxide Ion (OH-)- Has a charge of 1-

★ Acids and Bases ● Acid- Is a substance that increases the hydrogen ion concentration of a solution Ex. For example, when hydrochloric acid (HCl) is added to water, hydrogen ions dissociate from chloride ions: HCI---->H+ + Cl● Base- A substance that reduces the hydrogen ion concentration of a solution ★ PH Scale ● PH- A scale determining whether a solution is Basic, Neutral, or Acidic Ex. Pure water is #7 on the PH Scale (Neutral) Oven Cleaner is #14 on the PH Scale (Basic) Battery Acid is #1 on the PH Scale, having being the most Acidic solution (Acidic) ★ Buffers ● Buffer- A substance that minimizes changes in the concentrations of H+ and OH- in a solution -Human blood and many other biological solutions can be a buffer...