Density Review Lesson

Density Review Lesson

Density is a physical property of matter. Density is a comparison of the amount of matter to the amount of space. In other words, it is a measure of how closely "packed," or "crowded," the materials are in a defined area. Look at the two pictures. Each box is the same size. The balls in the box are the same size and have the same mass. Which box is more crowded?

What is density?

Draw

Which box is more crowded? Circle your choice.

Box B is more crowded; therefore, we can say it has more mass per unit of volume. Density is defined as mass per unit of volume, so box B has a greater density. Each element and compound has a unique density associated with it. The density of a material can be used to distinguish it from other materials.

​In order to calculate density, you have to know two measurements: the mass and the volume of the object.

To determine the mass of an object, you use a triple beam or electronic balance. Mass is expressed in grams.

If the object is a regular shaped object, such as a cube, you can determine the volume mathematically using the formula for volume. The formula for volume of a rectangular prism or cube is Volume=length x width x height​

Calculating Density

What if the object is irregular in shape, such as a rock? How do you determine the volume? You cannot determine the volume of an irregular shaped object using a mathematical formula. To determine the volume of an irregular shaped object, we must measure the fluid displacement using a graduated cylinder and water.

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Irregular Shaped Object

Draw

Now that we know the density of the unknown sample, use the chart and circle what material it must be.

Multiple Choice

The density of water is 1.0 g/cm³. If an object has a density greater than 1.0 g/cm³, it will sink. If the object's density is less than 1.0 g/cm³, the object will float.

Based on the density of the sample in the example above, will it float or sink?

• Sink

• Float