Rate of evaporation

Read our standard health & safety guidance

Lesson Organisation

Propanone is highly flammable; ensure that there are no sources of ignition nearby. Pupils could be asked to devise their own experiment, in which case teachers must check the plans before practical work starts, or they could be told how to vary the conditions and exactly what to do. A sample results table is available here (148 KB).

Apparatus and Chemicals

Eye protection

Per pair or group of students:
Microscope slides, 2 or 3
Access to warm water (not heated by an open flame)
Matchstick or similar
Timer
Dropper

Propanone (Highly flammable, Irritant), few cm³

Technical Notes

Propanone (Highly flammable, Irritant) Refer to CLEAPSS Hazcard 85

Procedure

HEALTH & SAFETY: Wear eye protection

a Put a drop of propanone onto a microscope slide and time how long it takes to evaporate.

b Change the conditions and repeat the experiment, ensuring that you record the conditions used and the time taken for each one. For example: warm the microscope slide by holding it in your hands, or placing in warm water and then drying; spread the drop out with a matchstick; for a cool air flow, fan with a book or similar; for a warm air flow, blow across the drop.

Teaching notes

Students should be able to observe that warmth, air flow and spreading out the drop increase the rate at which it evaporates.

Liquids evaporate below their boiling point. This is because as the particles move around and collide, some have more energy than the others allowing them to escape from the rest of the liquid as vapour. This results in the overall energy of the liquid (and therefore it’s temperature) decreasing.

This experiment lends itself well to being a planning exercise or alternatively there are some sample results tables available.

Health & Safety checked, April 2008