Learn Chemistry: Glossary


A glossary for Learn Chemistry explaining the meaning of chemistry terms used within this site.

Type of Activity

group work, working independently



Age Group

16 to Undergraduate
Term Definition
Reflux The heating of a reaction (in a suitable solvent) in a flask fitted with a condenser so that evaporated solvent is returned to the flask.
Residue The proportion of material that remains in the boiling flask after a distillation is completed.
Retention factor (Rf) A measurement of how far a compound has moved up a thin layer chromatography plate. It is calculated by dividing the distance the compound has moved by the distance the solvent has moved and so has a value between 0 and 1.
Rotoflow tap Often fitted to separating and addition funnels and is made up of a plastic tap which screws into a glass thread. The advantage of this kind of tap is the added control of addition rate.