Ch.3 Water and Life Flashcards
Polar molecule
A molecule with uneven distribution of charges in different regions of the molecule
Cohesion
The linking together of like molecules, often by hydrogen bonds
Adhesion
The clinging of one substance to another, such as water to plant cell walls, by means of hydrogen bonds
Surface tension
A measure of how difficult it is to stretch or break the surface of a liquid
Kinetic energy
The energy of motion
Thermal energy
The kinetic energy due to the random motion of atoms and molecules
Temperature
The average kinetic energy of the molecules in a body of matter, regardless of the volume
What happens when objects of different temperatures are brought together?
The thermal energy passes from the warmer to the cooler object until the two are at the same temperature
Heat
Thermal energy in transfer from one body of matter to another
Specific heat
The amount of heat that must absorbed or lost for 1g of a substance to change its temperature by 1 degree celsius
Why does water have such a high specific heat?
A calorie of heat causes a relatively small change in the temperature of water because much of the heat is used to break the hydrogen bonds before the water molecules can begin moving faster
What happens when the temperature of water drops slightly?
When the temperature of water drops slightly, many hydrogen bonds form, releasing a considerable amount of energy in the form of heat
Vaporization
When molecules move fast enough to overcome the molecular attractions and depart the liquid, they enter into the air as a gas
Why does water have a high heat of vaporization?
Due to the strength of hydrogen bonds, which must be broken before the molecules can exit from the liquid in the form of water vapor
Evaporative cooling
Process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state
Why does ice float on water?
Water is less dense as a solid than a liquid because it expands when it solidifies
Solution
A liquid that is a homogeneous mixture of two or more substances
Solvent
The dissolving agent of a solution (water is the most versatile solvent)
Solute
The substance that is dissolved
Aqueous solution
One in which the solute is dissolved in water (water is the solvent)
Hydration shell
The sphere of water molecules around a dissolved ion
Hydrophilic
Any substance that has an affinity for water (some substances can be hydrophilic without dissolving, ex: cotton)
Hydrophobic
Having no affinity for water (typically nonionic and nonpolar, since they cannot form hydrogen bonds)
Molecular mass
The sum of the masses of all the atoms in a molecule
Hydrogen ion
A single proton (H+). The dissociation of a water molecule leads to the generation of a hydroxide ion (OH-) and hydrogen ion (H+). (In water, H+ is not found alone but associates with a water molecule to form a hydronium ion)
Hydroxide ion
A water molecule that has lost a proton (OH-)
Hydronium ion
A water molecule that has an extra proton bound to it; H30+ commonly represented as H+
Acid
A substance that increases the hydrogen ion concentration of a solution
Base
A substance that reduces the hydrogen ion concentration of a solution
pH
A measure of hydrogen ion concentration equal to log[H+] and ranging in value from 0 to 14
Buffer
A substance that minimizes changes in the concentrations of H+ and OH- in a solution
Why are buffers important?
Allow biological fluids to maintain a relatively constant pH despite the addition of acids or bases
Ocean acidification
The process by which the pH of the ocean is lowered (made more acidic) when excess CO2 dissolute in seawater and forms carbonic acid (H2CO3)
