Chemical Any substance that has a definite composition Volume The amount of three dimensional space that an object occupies Mass A measure of the amount of matter Matter Anything that has mass and takes up space Atom The smallest unit of an element that maintains the properties of that element Element A pure substance made of only one kind of atom Weight A measure of the gravitational pull on matter Density The ratio of mass to volume or mass divided by volume Significant Figures All the digits known with certainty plus one final digit which is somewhat uncertain or is estimated