Density is a physical quantity defined as the ratio of mass to volume. For example, it can indicate how heavy an object (e.g. a certain foodstuff) is for a given volume. A well-known joke question is always: "Which is heavier: 1 kg of feathers or 1 kg of lead?". Since the density of feathers is much lower than that of lead, they would therefore take up a much larger volume than lead at a weight of 1 kg.
Density can also be used to compare the sugar content of foods in a simple way. We want to show you the difference between cola and Diet Coke in an experiment. There is also a direct correlation between the ageing of hen's eggs and density. In another experiment, we want to demonstrate whether a breakfast egg can still be eaten or whether it is better to avoid it.