Chapter 2

heat of vaporization

-A large amount of heat, 586 calories per gram, must be added to give water molecules enough energy of motion to break loose from liquid water and form a gas. -allows humans and many other organisms to cool off when hot

compounds

-Molecules whose component atoms are different -ex: carbon dioxide

orbital

-The locations where an electron occurs most frequently around the atomic nucleus define a path called an ______ -Within each energy level, electrons are grouped into______ -essentially the region of space where the electron "lives" most of the time

matter

-anything that occupies space and has mass -composed of elements and combinations of elements

chemical reactions

-atoms or molecules interact to form new chemical bonds or break old ones -as a result of bond formation or breakage, atoms are added to or removed from molecules, or the linkages of atoms in molecules are rearranged

make up more than 4% of the weight of living organisms

-calcium -phosphorus -potassium -sulfur -sodium -chlorine -magnesium

make up more than 96% of the weight of living organisms

-carbon -hydrogen -oxygen -nitrogen

non polar covalent bonds

-electrons are shared equally -characteristic of molecules that contain atoms of one element

polar covalent bonds

-electrons are shared unequally -characteristic of molecules that contain atoms of different elements

atom

-elements are composed of individual ______ -the smallest units that retain the chemical and physical properties of an element

covalent bonds

-form when atoms share a pair of valence electrons rather than gaining or losing them -designated by a pair of dots or a single line that represents a pair of shared electrons -shared orbitals extend between atoms at discrete angles and directions -three-dimensional forms -classified as nonpolar or polar

electronegativity

-he measure of an atom's attraction for the electrons it shares in a chemical bond with another atom -The more ______ an atom is, the more strongly it attracts shared electrons

atomic nucleus

-included in the basic structure of an atom -surrounded by one or more electrons

trace elements

-several other elements occur in organisms in quantities so small (<0.01%) -vital for normal biological functions -ex: iodine

hydration layer

-surface coat -reduces the attraction between the molecules or ions and promotes their separation and entry into a solution

Van der Waals forces

-weaker than hydrogen bonds -develop over very short distances between nonpolar molecules or regions of molecules when, through their constant motion, electrons accumulate by chance in one part of a molecule or another

surface tension

A measure of how difficult it is to stretch or break the surface of a liquid

dalton

A neutron and a proton have almost the same mass, about 1.66 × 10−24 grams (g)

molecules

Atoms, combined chemically in fixed numbers and ratios, form the ______ of living and nonliving matter.

chemical equations

Chemical reactions written in balanced form are known as

water lattice

Hydrogen bonds (constantly breaking and reforming) between water molecules produce a ______

tracers

Isotopes are also used in biological research as ______ to label molecules so that they can be tracked as they pass through biochemical reactions.

adhesion

Maintenance of the long columns of water in the tubes is aided by ______

hydrophobic

Nonpolar substances that are excluded by water and other polar molecules are identified as ______

hydrophilic

Polar molecules that associate readily with water are identified as ______

isotopes

The distinct forms of the atoms of an element, all with the same number of protons but different numbers of neutrons, are called _______

valence electrons

The electrons in an atom's outermost energy level

cohesion

The high resistance of water molecules to separation, provided by the hydrogen-bond lattice

2 electrons

The lowest energy level of an atom, the one nearest the nucleus, may be occupied by a maximum of

formula

The name of a molecule is written in chemical shorthand as a ______, using the standard symbols for the elements and using subscripts to indicate the number of atoms of each element in the molecule.

radioactivity

The nuclei of some isotopes are unstable and break down, or decay, giving off particles of matter and energy that can be detected as ______

hydrogen bonds

Very weak bonds; occurs when a hydrogen atom in one molecule is attracted to the electrostatic atom in another molecule

energy levels or shells

Within an atom, electrons are found in regions of space called ______

weight

a measure of the pull of gravity on an object

element

a pure substance that cannot be broken down into simpler substances by ordinary chemical or physical techniques

bases

are proton acceptors that reduce the H+ concentration of a solution

reactants

atoms or molecules entering a chemical reaction are called ______

mass number

based on the total number of protons and neutrons in the atomic nucleus

polar associations

create environments that tend to exclude nonpolar molecules

reversible

depending on conditions, it may go from left to right or from right to left

ionic bonds

extend their attractive force in all directions

atomic number

number of protons in the nucleus of each kind of atom

Avogadro's number

number of representative particles in a mole, 6.02 X 10^23

acid precipitation

polluting chemicals combine with atmospheric water to produce ______

protons

positively charged particles

acids

proton donors that release H+ (and anions) when they are dissolved in water, effectively increasing the H+ concentration

radioistope

radioactive isotope

nonpolar associations

reduce the surface area exposed to the surrounding polar environment

ice lattice

spaces the water molecules farther apart than the water lattice

buffers

substances that compensate for pH changes by absorbing or releasing H+

specific heat

the amount of energy as heat required to increase the temperature of a given quantity of water

mass

the amount of matter in an object

mole

the amount that contains 6.022 × 1023 atoms or molecules

solute

the molecules of a substance dissolved in water are

dissociate

the most critical property of water that is unrelated to its hydrogen-bond lattice is its ability to separate

neutrons

the nuclei of all atoms also contain uncharged particles called ______

concentration

the number of molecules or ions of a substance in a unit volume of space, such as a milliliter (mL) or liter (L)

molarity

the number of moles of a substance dissolved in 1 L of solution

molecular weight

the sum of the atomic weights of all of the atoms in the molecule

products

those leaving a reaction are the ______

calories

what specific heat is measured in

solution

where they are suspended individually, surrounded by water molecules