Density is one of many science terms that get thrown around often--along with mass, volume, acceleration and area. Density is the concentration of matter in an object. In layman's terms, the density of an object is the amount of "stuff" inside of it. For example, a rock has a lot more density than a sponge, because there is more material inside each bit of rock.
If the object is a sphere or another type of regular object, you may be able to find an equation to calculate its volume without using the water displacement method.
If an object has holes in it, the water displacement test will not work. Instead, you will have to create a model of the object that does not contain holes and use the model in the water displacement test.
In order to calculate an object's density, you must first calculate its mass and volume. To calculate its mass, use a triple-beam balance. Place the object on one end and move the weights until they balance. Write down the mass of the object.
There are two main ways to calculate an item's volume. If the object is a cube, you can multiple its width, length and height together to obtain its volume.
If the object has irregular edges, you can calculate its mass by submerging it in a graduated cylinder or similar container full of water. Then, measure the amount of water it displaces. For example, if the water level rose from 15 ml to 17 ml, the object displaced 2 ml of water. Write down the volume of the object.
To calculate the object's density, divide its mass by its volume. The equation for density is "density = mass/volume."
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