Density Lab

Investigating Density

Density is a comparison between the mass  and volume of a substance.  Mass is the amount of matter in a substance and volume is the amount of space something takes up.  We know that the different layers of the Earth (the crust, mantle, and core) have different densities.  The density of the crust varies from 2.7 g/cm³ to 3.0 g/cm³.  The density of the mantle is 3.3 g/cm³ to 5.7 g/cm³.  

To understand the layers of the Earth better we will investigate how materials with different densities interact with each other.

Materials

• samples of  dishwashing soap, baby oil, water, and glycerine

• 100-mL graduated cylinder

• 4 small cups

• 4 pipettes

• safety glasses

Predict

1. Collect a sample of each of the four liquids you will use to build your density column.

2.  Working by yourself, observe the liquids and use what you know about density to predict which liquids are more dense than others. Remember that density is a measure of how close together the particles of a substance are packed. In a denser substance, particles are packed more tightly. List the liquids from most dense to least dense.

3. Still working by yourself, sketch the way you think the liquids will stack in your science notebook. Where do you think the liquid will end up in the column? Which liquid would be next? Why? Use colors and labels so that your diagram is clear to someone else.

4. Before you actually place the liquids in the cylinder, share your prediction with your group. Describe why you think the liquids will stack according to your prediction.

Investigate

1. Use the pipette to place each liquid in the graduated cylinder, starting with the bottom layer. Drop the liquids in the order your group predicted. Try to drip each liquid down the center without touching the sides of the graduated cylinder. It is all right if the liquids mix a little. 

2. Observe your density column until the liquids have settled. They may move after you have layered them. 

3. Next to your prediction sketch, draw the ordering of the liquids as you saw in your results. Use colors and labels to make sure you sketch an accurate density column showing how each of the liquids was layered. 

Group Discussion 

1. Compare your prediction sketch to the sketch of your results. How are they the same? How are they different? 

2.  Which liquid in your density column has the greatest density? What makes you think this liquid is the most dense?

3. Which liquid is the least dense? What makes you think this liquid is the least dense?