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During the boiling of a liquid, the bubbles of vapour form around rough areas or small air bubbles. If a liquid is boiled in very clean, smooth glassware it can be difficult for bubbles of vapour to form. The liquid can rise above its boiling point - it is said to be superheated. Suddenly, one large bubble of vapour forms rapidly, disturbing the hot liquid violently. This effect is known as bumping, and is hazardous. |
If you are boiling a liquid in a flask or beaker, the addition of a few anti-bumping granules limits the chance of bumping occurring.
If you are boiling a liquid, use the wider bore boiling tube (rather than a test tube) and don't fill it more than about a fifth full. Gently shake the liquid continuously to prevent hot spots from forming and avoid prolonged heating. Make sure that the open end of your boiling tube is not pointing in anyone's direction, and remember people move! You can find out more details about heating with a Bunsen burner here.
Video - heating a liquid
