| Term | Definition |
|---|
| element | a substance that can't be broken down into simpler chemical substances |
| atom | the smallest particle of an element that has the characteristics of that element, it is called the building block of matter |
| nucleus | the center of an atom including positive protons and neutral neutrons; they are positively charged |
| isotopes | atoms of the same element with the same number of protons but different numbers of neutrons, they are radioactive and help in medicine |
| compound | a substance that is composed of atoms of two or more different elements that are chemically combined |
| covalent bond | a force that holds together atoms that share electrons, between most compounds and between two non-metals |
| molecule | a group of atoms held together by covalent bonds with no overall charge |
| ion | a charged particle made of atoms |
| ionic bond | the bond between two ions of opposite charge, it occurs when one atom loses an electron and becomes positive and another atom gains an electron and becomes negative and the two atoms bond |
| metabolism | all of the chemical reactions that occur within an organism; chemical reactions occur when bonds are formed or broken |
| mixture | a combination of substances in which the individual components retain their own properties; the components don't combine chemically |
| solution | a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent); the solvent dissolves the solute |
| pH | a measure of how acidic or basic a solution is; the scale ranges from below 0 to above 14 |
| acid | a substance that forms hydrogen ions in water; has a pH of less than 7 |
| base | a substance that forms hydroxide ions in water; has a pH of more than 7 |
| polar molecule | a molecule with unequal distribution of charge, it has a positive and negative end; polar water molecules attract ions and polar molecules and dissolve them |
| hydrogen bond | a weak bond formed by the attraction of opposite charges between hydrogen and oxygen |
| diffusion | the net movement of particles from an area of higher concentration to an area of lower concentration; results from random movement of particles (Brownian motion) is a slow process affected by concentration, temperature, and pressure |
| dynamic equilibrium | condition in which there is continuous movement but no overall concentration change; materials move into and out of the cell at equal rates |
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