Biology 2.1-2.4

What is an element defined as?

Substances that cannot be broken down to any other substance by ordinary chemical means.

What are the three subatomic particles of an atom?

Electrons, protons, and neutrons.

What is the charge and location of a proton?

Positively charged, located in the nucleus.

What is the atomic number?

The number of protons in the nucleus.

What is atomic mass?

The sum of all protons and neutrons in the atomic molecule.

What defines a cation?

A positively charged ion.

What defines an anion?

A negatively charged ion.

What is an isotope?

Different forms of the same element with the same number of protons but different number of neutrons.

What are valence electrons?

Electrons in the outermost energy level of an atom.

List important elements found in living systems.

Carbon, Hydrogen, Oxygen, and Nitrogen.

What are trace elements? Give an example.

Elements required in minute amounts; example: Zn and I.

What determines the chemical behavior of an atom?

The number and arrangement of electrons in its valence shell.

What is electronegativity?

An atom's attraction for the covalent bond.

Which atoms are likely to form ions?

Atoms with nearly full or nearly empty valence shells.

How are molecules formed from atoms?

When an atom shares two or more valence electrons through covalent bonds.

Contrast polar and nonpolar covalent bonds.

Nonpolar: Electrons shared equally; Polar: Electrons shared unequally.

What causes hydrogen bonding?

A hydrogen atom covalently bonded to an electronegative atom attracts another electronegative atom.

Define reactants in a chemical reaction.

Original molecules that undergo change.

Define products in a chemical reaction.

New molecules resulting from the reaction.

How does water's structure lead to hydrogen bonds?

Water forms hydrogen bonds because the molecule is asymmetrical with slightly positive hydrogens attracted to slightly negative oxygen atoms.

What is cohesion in relation to water?

Water molecules held together collectively by hydrogen bonds.

What is adhesion in relation to water?

Water molecules held together by other polar molecules through hydrogen bonding.

Define specific heat.

The amount of heat that must be absorbed or lost for 1g of that substance to change by 1°C.

What is heat of vaporization?

The amount of energy required to change 1g of a substance from liquid to gas.

What does evaporative cooling do?

Stabilizes temperature in organisms and bodies of water.

What is a solvent?

The dissolving agent of a solution, e.g., water.

What is a solute?

The substance that is dissolved, e.g., salt.

Differentiate hydrophobic and hydrophilic substances.

Hydrophilic: Affinity for water; Hydrophobic: No affinity for water.

What are the dissociated products of water?

Hydroxide ion (OH-), Hydrogen ion (H+), Hydronium ion (H3O+).

How is an acid defined?

Any substance that dissociates in water to increase the H+ concentration.

How is a base defined?

Any substance that combines with H+ in water and lowers the [H+].

What is the pH scale?

A logarithmic scale where each unit change in pH represents a 10-fold change in [H+].

What function do buffers serve in stabilizing pH?

Buffers resist changes in pH by releasing or absorbing hydrogen ions when bases or acids are added.