Unit 1 AP bio Key Vocabulary

Hydrogen Bond

A weak bond/interaction BETWEEN two molecules; one with a negative charge and one with a positive charge.

Ex: water molecules—the slightly positivite hydrogen of one water molecule bonds with the slightly negative oxygen in another water molecule

Covalent Bond

A chemical bond WITHIN a molecule where atoms are held together by the force of an electron.

Ex: hydrogen is held together by the negatively charged oxygen.

Cohesion

The ability of water to stick/bond with other substance similar to water and form a hydrogen bond.

Ex: water and water

Adhesion

The ability of water to form a hydrogen bond with a substance different from water.

Ex: water and acid.

Polar (what water is)

Molecules that have an uneven distribution of charge

Polar covalent bonds

When electrons are shared unequally between atoms; unbalanced electronegativity

Nonpolar

Molecules that have an even distribution of charge

Nonpolar covalent

Electrons are shared equally between atoms because the atoms have similar electronegativities

Electronegative atoms

An atom with a high tendency to attract electrons toward its nucleus; the more electronegative an atom, the more it pulls on the shared electrons in a bond

High heat capacity

The property of water to absorb excessive amounts of thermal energy before changing it's chemical state which allows water to resist sudden changes in temperature

Ex: when our body absorbs excess heat such as in exercise, the water in your blood stream and tissue absorbs this heat and allows for the regulation of body temperature and water molecules on our skins surface absorbs heat from your body: becoming energized when you sweat. Also allows for climate regulation as large bodies of water store excess amounts of heat during the summer and slowly release it into the atmosphere during the winter.

Surface Tension

The property of water that allows water to minimize surface area as a result of the cohesive forces between liquid molecules and water’s polarity.

Expansion upon freezing

The property of water that allows hydrogen bonds between water molecules to expand as the temperature drops which makes ice float on water because it becomes less dense when it's solid due to water’s polarity.

Ionic Bonds

A bond where electrons are transferred between molecules: ions have opposite charges that attract each other.

Hydrophilic

Polar molecules attracted to water that therefore dissolve in water

Hydrophobic

Nonpolar molecules that despise water therefore do not dissolve in water (ex: oil and water and the fats((lipids)) that make up the cell membrane).

Capillary Action

The ability of water to move up against gravity up a narrow tube using the forces of adhesion and cohesion; thus how plants get water.

Solvent

(What water is) water’s capability of dissolving numerous polar substances due to its polarity .

Ex: waters solvency allows our cells to absorb nutrients and oxygen.

Acids

Molecules that donate H+ (hydrogen) ions to a solution which lowers its pH and increase the acidity; when there are more hydrogen ions in a solution than OH(hydroxide) ions in a solution, that solution is acidic.

Ex: hydrochloric

Base

A substance that decreases hydrogen ion concentration (H+) which increases pH and has a pH above seven (which is our body’s neutral pH level to maintain homeostasis).

Ex: sodium hydroxide has less hydrogen ions than hydroxide, therefore it is not acidic and instead basic

pH Scale

A measure of the acidity of a solution that ranges from 0 to 14: a solution above 7 is basic and below is acidic. This scale determines pH level by measuring the concentration of hydrogen ions.

Everything on a pH scale is a tenfold increase in hydrogen concentration (like when 7 goes to 6 the substance is now ten times more acidic)

Dehydration Synthesis

The chemical process where two molecules are joined together by covalent bonds to form a larger molecule which in the process removes a water molecule.

Hydrolysis Reactions

A chemical reaction that breaks a covalent bond between molecules by adding water which breaks down larger molecules into smaller, simpler ones.