Quantitative properties - associated with numbers Units must always be specified Scientific measurements use the metric system SI Units Seven base units are used by SI Prefixes are used to modify powers of 10 of these units Length and Mass Mass - the measure of the amount of material in an object Temperature - a measure of hotness and coldness (physical property) Heat flows spontaneously from the hotter object to the colder one Celsius scale - created considering water's boiling and freezing points Kelvin scale - created so that 0K is the lowest possible attainable zero (absolute zero) The Kelvin and Celsius scales use the same-sized units around a different zero Derived SI Units - obtained by the multiplication or division of one or more base units