You can calculate density by finding the mass of an object and dividing it by its volume. To find the volume of a solid is easy. You just multiply length times width times heigth. To find the mass of an object, you can place it on a balance scale to determine its mass. But, what if you are trying to find the density of an object like a marble or a nail? This is an irregularly shaped object. You cannot just measure the sides of a marble or a nail and multiply the length times the width times the heigth. So, the density of an irregular solid is determined by using the same formula for density, only you must find the volume of the object by water displacement.

Calculating the density of a regular solid such as a cube is easy. You measure the sides of the object with a metric ruler and calculate the volume: length times width times heigth. How can you find the volume of an irregularly shaped object?

Curtiss is using a graduated cylinder to determine the volume of an irregularly shaped object by water displacement.

Emily and John are measuring the mass of a bolt.

Kayla and Mandie work together to find the mass of a nail by using a balance scale. They will use a graduated cylinder to find the volume of the nail by water displacement. Now that they have these measurements, they can calculate the density of an irregularly shaped object. Density equals mass divided by volume.

Andrea slowly lowers the bolt into the graduated cylinder. Chelsea watches the water level increase. They record the water displacement by finding the difference in the first and second water levels.

Jason is trying very hard to read the volume of water in the graduated cylinder. To get an accurate measurement, Jason knows he must find the meniscus or the bottom of the curve.

Teams work together using a balance to find the mass of a bolt.

Clinton is using his balance to find the mass of a bolt.

Stevie and Dani work together to find the volume of the bolt. First, you read the water level in the graduated cylinder. Second, place the bolt into the graduated cylinder. If you tie a string around the bolt, you will be able to lower it into the cylinder without splashing out any water. Next, get a second reading of the water level and find the difference. The difference in the water level is called water displacement and you can use this to find the volume of an irregularly shaped object like a bolt.

Erin and Brandon work together to find the volume of a marble.

Sarah and Emily watch Colin and Cody find the mass of a nail.