Density is the measure of a material's mass per unit volume, used in many aspects of science, engineering and industry. Density can be calculated by dividing an object's mass by its volume. Since different materials have different densities, measuring an object's density can help determine which materials are in it. Finding the density of a metal sample can help to determine its purity.

When measuring liquids and regularly shaped solids, mass and volume can be discovered by direct measurement and these two measurements can then be used to determine density. Using a pan balance, determine and record the mass of an object in grams. Using a vernier caliper or ruler, measure the length, depth and width of the object in centimeters. Multiply these three measurements to find the volume in cubic centimeters. Divide the object's mass by its volume to determine its density. Density is expressed in grams per cubic centimeter or grams per milliliter.

For an example, watch the video below:

To calculate the density of solids with irregular surfaces, volume must be determined by another method. Instead of measuring the surface area directly, use a graduated cylinder to find the object's volume. Pour water into the graduated cylinder until it reaches a known level. This level can be measured by the markings on the cylinder's surface, which display the volume of water in milliliters. Add the object to the water and record the new water level. The difference between the new water level and the original level will be the object's volume. This measurement is taken in milliliters, which are interchangeable with cubic centimeters. Once volume is determined, apply the same equation as above.

Archimedes' principle states that a body's immersion in a given fluid will produce a buoyant force acting upward on it. This force will be equal to the weight of the displaced fluid. An object of unknown density will either float or sink within a given fluid depending on that fluid's density relative to the object's. To determine roughly how dense an object is, place it in various fluids of known density and observe the result. If it sinks, it is more dense than the fluid. If it floats, it is less dense.