Distribute a tray of materials to each group, but hold back the empty containers and the second container of mineral oil (the one containing 40 grams of oil) for now. Draw attention to the new material — the gravel — and point out that all the materials take up the same amount of space. Check for understanding:

• Do these materials have the same weight or the same volume?

• the same volume

Students will fill containers with equal weights (40 grams) of these same materials. Then they will see how the volumes compare. But first you want them to predict what the results will be, and how the materials will line up in volume order.

• How do you think the volumes will compare when every container has 40 grams of material?
• What will the order be, from least volume to most volume?

Ask students to take five minutes to record their thoughts and predictions in their science notebooks [What is the volume of 40 grams of an earth material?].  If they are stumped, suggest that they go back to their weight data recorded earlier in their notebooks.

You may need to remind students that they are working with the bulk volumes of the granular materials. The volume will include the air between the grains of sand, organic soil, and gravel.