Imagine three identical buckets:  one filled with water, one filled with shredded leaves and twigs, and one filled with sand. Each material takes up the same amount of space, but do they weigh the same? It’s an old conundrum, and one that will take students four investigations to unravel completely.

In this investigation, students share what they know about volume, then compare the weights of equal volumes of two liquids and two granular solids using a digital scale. By the end of the investigation students will understand that volume describes the amount of space something takes up, that equal volumes of different materials can have different weights, and that some materials are "heavy for their size."

Learning Goals

• Distinguish weight and volume
• Learn how to use a digital scale
• Understand that "heavy for size" is property of materials

Sequence of experiences
1. Ask the question	All Class	10 Mins
2. Compare the weights	Small Groups	20 Mins
3. Make meaning	Discussion	15 Mins

Materials and Preparation

For the class:

• Post the investigation question in a place where all students can see it.
• Make a class data table for recording the weights of the four samples; an example is found in Step 2.
• 1 unopened ream of 8.5 x 11 in. paper (not in kit)
• 1 150cc container approximately one–quarter filled with fresh water
• 1 150cc container approximately three–quarters filled with fresh water
• 1 150cc container filled to the top with sand
• 1 150cc container filled to the top with organic soil
• 1 20oz cup

For each tray:

• 1 capped 150cc container containing exactly 40cc of fresh water (from Investigation 1.1)*
• 1 capped 150cc container containing exactly 40cc of mineral oil (from Investigation 1.1)*
• 1 capped 150cc container containing exactly 40cc of sand*
• 1 capped 150cc container containing exactly 40cc of organic soil*
• 1 capped 150cc container, empty (to establish tare weight)
• 1 digital scale

* Note: These 4 containers are used again in the next investigation. It is key to this investigation that these four containers holding water, mineral oil, sand, and organic soil all have volumes that are close as possible to 40 cc's. All should appear to hold the same volume. Tap the containers holding sand and organic soil to settle the material in those two containers.