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Name: Linda L.
Status: educator
Age: 40s
Location: N/A
Country: N/A
Date: 1999-2001

How can I explain to my 5th graders the difference between volume, capacity and weight?

Probably one of the best ways to show the difference between volume and weight is to get a brick and a piece of Polystyrene foam that is the same size as the brick. The kids can determine the volume of both by measuring the length, width, and depth of both objects. They will see they are the same, but when they weigh them on a scale, they will see the difference in weight. This would also be a great time to tell them about density.

Chris Murphy


Volume is a word that is intended to describe the three dimensional size of an object or space. For something like a box, one calculates its volume my multiplying its length by its width by its height. You know, the old familiar V = L x W x H. For something with an irregular shape, like an ocean -- things get much more complicated. In the end, however, volumes are expressed in cubic units such as, cc or cubic feet or cubic kilometres, etc.

Capacity is a term that refers to a measuring vessel or a container of known volume. We speak of a graduated cylinder as having a capacity of 100 cc or 100 mL. If one were to measure the capacity of an irregular vessel like a vase, by filling it with water and then pouring the water into a graduated vessel. one would have indirectly determined the volume of the vase and thus, its capacity.

Weight is an entirely different matter, which on its face, can have little to do with either volume or capacity. We cannot say something is heavy just because it is big. Consider a balloon. Nor can we say something is light just because it is small. Consider the weight of a rock that's much smaller than the balloon, yet much heavier. Demonstrate this by using a scale, a balloon, and a rock to show the students.

Instead of being size-related, weight is a measure of the gravitational force between an object and the earth. If you weighed a pillow and then squeezed it down to the smallest possible size, you would have reduced it volume and made no appreciable change in its weight.

Weight and volume are linked by an expression called density where d = m / V. Dense objects have relatively small volumes for their weight. The uncompacted and compacted pillow illustrate this. The uncompacted pillow has a low density because it has a large volume. Likewise, the compacted pillow has a much higher density because its volume has been reduced. All the while, the pillow's weight is essentially the same.

I hope this is of assistance,


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