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Biology for Health Science
Chapt 2
45
Biology
Undergraduate 1
01/27/2009

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Term
Matter
Definition
Anything that occupies space and has mass.Matter, in forms as diverse as rock, water, gases, and living organisms, is composed of chemical elements
Term
Element
Definition
A substance that cannot be broken down to other substances by chemical means.
Term
Trace Element
Definition
An element that is essential for life but required in extremely minute amounts.
Term
Which four chemical elements are most abundant in living matter?
Definition
Oxygen, carbon, hydrogen, and nitrogen
Term
Organism
Definition
A living thing.
Term
Compound
Definition
A substance containing two or more elements in a fixed ratio. For example, table salt (NaCl) consists of one atom of the element sodium (Na) for every atom of chlorine (Cl).
Term
Atom
Definition
The small unit of matter that retains the properties of an element
Term
Proton
Definition
A subatomic particle with a single positive electrical charge, found in the nucleus of an atom.
Term
Electron
Definition
A subatomic particle with a single negative electrical charge. One or more electrons move around the nucleus of an atom.
Term
Neutron
Definition
An electrically neutral particle (a particle having no electrical charge), found in the nucleus of an atom.
Term
Nucleus
Definition
(plural, nuclei) (1) An atom’s central core, containing protons and neutrons. (2) The genetic control center of a eukaryotic cell.
Term
Atomic number
Definition
The number of protons in each atom of a particular element. All atoms of a particular element have the same unique number of protons.
Term
Mass number
Definition
The sum of the number of protons and neutrons in an atom’s nucleus.
Term
Atomic Mass
Definition
The approximate total mass of an atom; also called atomic weight. Given as a whole number, the atomic mass approximately equals the mass number.
Term
Isotope
Definition
A variant form of an atom. Isotopes of an element have the same number of protons but different numbers of neutrons.
Term
Nucleus
Definition
1) An atom's central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.
Term
Why are radioactive isotopes useful as tracers in research on the chemistry of life?
Definition
Organisms incorporate radioactive isotopes of an element into their molecules just as they do nonradioactive isotopes, and researchers can use special scanning devices to detect the presence of the radioactive isotopes.
Term
Definition
Only electrons are directly involved in the chemical activity of an atom. The farther an electron is from the nucleus, the greater its energy
Term
Definition
By transferring or sharing electrons, atoms complete their outer shells. These interactions between atoms create chemical bonds.
Term
Ion
Definition
An atom that has gained or lost one or more electrons, thus acquiring a charge.
Term
Ionic Bond
Definition
A chemical bond resulting from the attraction between oppositely charged ions.
Term
Covalent bond
Definition
An attraction between atoms that share one or more pairs of outer-shell electrons; symbolized by a single line between the atoms.
Term
Double bond
Definition
A type of covalent bond in which two atoms share two pairs of electrons; symbolized by a pair of lines between the bonded atoms.
Term
Molecule
Definition
Two or more atoms held together by covalent bonds.
Term
electronegativity
Definition
The attraction of a given atom for the electrons of a covalent bond. The more electronegative an atom, the more strongly it pulls shared electrons toward its nucleus.
Term
nonpolar covalent bond
Definition
A covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
Term
polar covalent bond
Definition
A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
Term
polar molecule
Definition
A molecule containing polar covalent bonds.
Term
hydrogen bond
Definition
A type of weak chemical bond formed when the partially positive hydrogen atom participating in a polar covalent bond in one molecule is attracted to the partially negative atom participating in a polar covalent bond in another molecule (or in another part of the same macromolecule).
Term
Cohesion
Definition
The binding together of like molecules, often by hydrogen bonds.
Term
adhesion
Definition
The attraction between different kinds of molecules.
Term
surface tension
Definition
A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.
Term
Heat
Definition
Thermal energy; the amount of energy associated with the movement of the atoms and molecules in a body of matter. Heat is energy in its most random form.
Term
Temperature
Definition
A measure of the intensity of heat in degrees, reflecting the average kinetic energy or speed of molecules.
Term
Solution
Definition
A liquid consisting of a homogeneous mixture of two or more substances, consisting of a dissolving agent, called the solvent, and a substance that is dissolved, called the solute.
Term
Solvent
Definition
A liquid consisting of a homogeneous mixture of two or more substances, consisting of a dissolving agent, called the solvent, and a substance that is dissolved, called the solute.
Term
Acid
Definition
A substance that increases the hydrogen ion concentration in a solution.
Term
Base
Definition
A substance that decreases the hydrogen ion (H) concentration in a solution.
Term
PH scale
Definition
A measure of the relative acidity of a solution, ranging in value from 0 (most acidic) to 14 (most basic). The letters pH stand for potential hydrogen and refer to the concentration of hydrogen ions (H).
Term
Buffer
Definition
A chemical substance that resists changes in pH by accepting hydrogen ions from or donating hydrogen ions to solutions.
Term
Definition
An acid is any substance that increases the H+ concentration of a solution. A base is any substance that reduces the H+ concentration of a solution. Move your cursor up or down in the pH scale to add acid or base to our solution.
Term
acid precipitation
Definition
Rain, snow, or fog with a pH below 5.6.
Term
Chemical reaction
Definition
The making and breaking of chemical bonds, leading to changes in the composition of matter.
Term
Reactant
Definition
A starting material in a chemical reaction.
Term
Product
Definition
An ending material in a chemical reaction.
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