Understanding mass, weight, volume and density

There are various basic measures that are taken in order to quantify biomolecules. Of these arguably the most important are mass, weight, volume and concentration. Often the term mass is confused with that of weight, but it is important to recognize that they are actually quite different. 

Mass is the quantity of matter in a given object and is independent of gravity. 

Weight is the force of gravity on a given object and is calculated as mass multiplied by gravity. 

While an object will always have a given mass, its weight will vary depending on gravity. So an object with the same mass will have a different weight on Earth compared with the Moon or a weightless environment (such as in space). 

Scientific measurements are based on mass (not weight), and the Syst4me International (SI) unit is the gram (g). For further details on SI units and common prefixes please see Appendix 1. 

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