Density Grade 8 Density, Mass and Volume You have probably heard the terms mass and volume before in Natural Sciences and Mathematics. But what about density? Have you ever used this word before? Perhaps you have heard someone describe a cake as very dense? What does this mean? This section introduces us to physical quantities that are important when we study science. Two of these quantities, namely mass and volume, are fundamental properties of matter. We are going to discuss them first, then we will introduce density. Density is another property of matter that is very closely related to the first two. Mass • The mass of an object or a substance tells us how much matter it consists of. The greater the mass of an object, the more matter it contains. • Mass is measured in kilograms (kg). When we measure the mass of small objects or small amounts of matter we often measure in grams (g) or even milligrams (mg). • 1kg = 1000g • 1g = 1000mg Volume • The amount of space that an object occupies is called its volume. • Volume is measured in litres and is calculated by multiplying the length, width and height of an object. • A litre is the space inside a cube that is 10 cm wide, 10 cm long and 10 cm deep. When calculating volume, 1 cm x 1 cm x 1 cm = 1 cm3. This is the same as 1 ml. That means that 10 cm x 10 cm x 10 cm = 1000 cm3 which equals 1000 ml or 1 litre. What is the volume of milk? What is the volume of mango juice? Density • Density is a measure of how much mass of a material fits into a given volume. • We say density is the ratio of mass to volume. • We can write a mathematical relationship to show this ratio as follows: density = mass/volume m D V