Practical Activity for 14-16
Comparing the masses of equal volumes of liquids, to develop a general feeling for density.
Apparatus and Materials
For each student group
- Perspex containers (rectangular boxes, open at top), 2
- Balance, lever-arm or top-pan
- Marker pen
- Sand, wheat, rice or dried peas
- Liquids (e.g. water, paraffin, brine, cooking oil and syrup)
Health & Safety and Technical Notes
Choose liquids that are low risk.
- The transparent containers will allow you to measure and weigh standard quantities of liquids and other
pourablesubstances. Mark a line on the outside of each container at a height of, say, 8 cm.
- Fill a container to the line with sand. Weigh the container to find its mass.
- Repeat with water, and then another liquid. How do the different substances compare?
- The object of this experiment is not to make systematic measurements of liquid densities but rather to extend a general developing feeling for density. It can be used as an extension activity to following ...
counting cubesapproach to volume measurement is relatively easy
- Those students who raise the question of the weight of the box itself will weigh it of their own accord, but the teacher should not give a general instruction to do this.
- Weighing sand might lead to a discussion of an
averagedensity for the sand and spaces combined. Start such a discussion by trying wheat or dried peas. Considering water after this may lead to a discussion once again of atoms.
- When the box is filled with sand or rice then there are spaces between the grains. A discussion about the average density of air and sand is necessary. However when the box is filled with water, what is it they are measuring? What is between the atoms? [Empty space.]
This experiment was safety-tested in July 2007