Students now have some weight data, and they have some rules for making a good weight line. They are ready for the next challenge: Construct a weight line that will help them see — really see — how much heavier some earth materials are than others.

As they work through the challenge, students apply their rules, grapple with some geometry and arithmetic, and consider what their weight line shows them about their earth materials. They then compare the two ways they have represented their data: in the data table and on the weight line. Then also try to solve some weight line puzzles. By the end of the investigation, students will have a better visual understanding of what it means to be "heavy for size."

Learning Goals

• Recognize that data tables and weight lines can both display weight data
• See that a weight line is a good way to show how much more one thing weighs than another

Sequence of experiences
1. Ask the question	All Class	5 Mins
2. Build weight lines	Individual	20 Mins
3. Reflect	Discussion	10 Mins
4. Weight line puzzles	All Class	10 Mins

Materials and Preparation

For the class:

• Post the investigation question in a place where all students can see it.
• Class data table for earth material weights (from the first investigation)
• Class list of rules for a good weight line (from the last investigation)

For each tray:

• 1 capped 150cc container with exactly 40cc of fresh water (from the last investigation)*
• 1 capped 150cc container with exactly 40cc of mineral oil (from the last investigation)*
• 1 capped 150cc container with 40cc of sand (from the last investigation)*
• 1 capped 150cc container with 40cc of organic soil (from the last investigation)*
• 4 strips of adding machine tape; strips can vary in length from 40-60 cm.

* These 4 containers will also be used in the next investigation.