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.

Fill in the Blanks

We calculate density using a formula. What is that formula for calculating density?

Density = _____/_____

​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

Fill in the Blanks

Determine the volume of the object using the formula on the previous slide.

V=

cm³

Fill in the Blanks

Determine the volume of the object using the formula on the previous slides.

V=

cm³

Fill in the Blanks

Determine the volume of the object using the formula on the previous slides.

V=

cm³

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.

​

Irregular Shaped Object

Fill in the Blanks

Look at the graduated cylinder. What is the volume of water in mL?

Fill in the Blanks

Look at the graduated cylinder now. What is the new volume of water in mL?

Fill in the Blanks

To determine the volume of the sample, you need to determine how much water was displaced. To do this, you subtract the initial, or beginning, volume from the final volume. How much water was displaced in the previous 2 slides?

Fill in the Blanks

To find the density of the substance, we also need to know the mass. What is the mass in grams of the sample?

Fill in the Blanks

Using the mass and volume that you found earlier, calculate the density of that unknown sample (D=m/v)

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