This colourful experiment will help you and your children understand density better. Density is the mass of a material per unit volume, and it is a fixed number for each material. The density of water is 997 kg/m³; however, we can increase it by adding salt and sugar to it. In this experiment, we were adding a different amount of salt to each glass of water. When the salt dissolves, it increases the mass of water without changing the volume very much, which means that the saltwater solution's de