Vocab 2

acid- A substance that increases the hydrogen ion concentration of a solution.

aqueous solution- a solution in which water is the solvent

Atom- the smallest unit of matter that retains the properties of an element

 atomic mass total mass of an atom

 base- A substance that decreases the hydrogen ion concentration in a solution.

 buffer- a chemical substance that decreases the hydrogen ion concentration in a solution

chemical bond- An attraction between two atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells.

chemical reaction- A process leading to chemical changes in matter; involves the making and/or breaking of chemical bonds.

Compound- a substance containing two or more elements in a fixed ratio

 covalent bond- An attraction between atoms that share one or more pairs of outer-shell electrons; symbolized by a single line between the atoms.

 Electron- A subatomic particle that has a single unit of negative charge, one or more of these move around the nucleus.

 element- A substance that cannot be broken down into simpler substances evaporative cooling The property of a liquid whereby a body becomes cooler during evaporation, owing to a loss of highly kinetic molecules to the gaseous state.

 half-life- The amount of time it takes for 50% of a sample of a radioactive isotope to decay.

hydrogen bond- A type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule.

Ion- an atom or molecule that has gained or lost one or more electrons ionic bond the attraction between oppositely charged ions

 isotope- A variant form of an atom. Isotopes of an element have the same number of protons but different numbers of neutrons.

 mass- A measure of the amount of matter in an object mass number the sum of the number of neutrons and protons in an atomic nucleus matter anything that has mass and occupies space

 Molecule- A group of two or more atoms held together by covalent bonds.

 Neutron- An electrically neutral particle (a particle having no electrical charge), found in the nucleus of an atom.

 Periodic Table of Elements- a table listing all the known elements and their properties

 pH- hydrogen ion concentration

pH- scale a measure of the relative acidity of a solution, ranging from 0 (most acidic) to 14 (most basic)

 polar molecule- molecule with an unequal distribution of charge, resulting in the molecule having a positive end and a negative end product an ending material in a chemical reaction

 Proton- A subatomic particle that has a positive charge and that is found in the nucleus of an atom

radioactive isotope- An isotope whose nucleus decays spontaneously, giving off particles and energy.

Reactant- A starting material in a chemical reaction solution A liquid that is a homogeneous mixture of two or more substances.

 solvent- the dissolving agent of a solution

trace elements- elements required by an organism in only minute quantities atomic number the number of protons in an atom