2. Heavy for Size:  Investigation 2.4

# Same weight, same volume?

## Plan Investigation 2.4

By now students are aware that materials having the same volume can have different weights. But do they understand that the reverse must also be true? In this investigation they confirm that materials having the same weight can have different volumes.

Students review the weight data for the materials they have studied so far — sand, water, mineral, and organic soil. Then they predict how the volumes of these materials will compare if the weights are held constant. They also consider a new material: gravel. They check their predictions by measuring out equal weights of the materials and comparing the volumes.

By the end of the investigation, students will have a clearer understanding that weight and volume are different properties of earth materials. They will also have a deeper understanding of what it means to say that a material is "heavy [or light] for its size."

### Learning Goals

• See whether equal weights of different materials have the same volume
• Distinguish weight and volume
Sequence of experiences
1. Ask the question All Class 10 Mins
2. Predict volumes Small Groups 10 Mins
3. Test predictions Small Groups 15 Mins
4. Discuss the results Discussion 10 Mins

### Materials and Preparation

For the class:

• Post the investigation question in a place where all students can see it.
• Post the investigation question for Investigation 2.1., i.e., “Same volume, same weight?”
• 4 classroom weighing stations:
• 1 water weighing station:
• 1 pitcher of water
• 2 pipettes
• 1 digital scale
• 1 gravel weighing station:
• 1 container of gravel
• 2 spoons
• 1 digital scale
• 1 organic soil weighing station:
• 1 container of organic soil
• 2 spoons
• 1 digital scale
• 1 sand weighing station:
• 1 container of sand
• 2 spoons
• 1 digital scale

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)*
• 1 capped 150cc container with 40cc of gravel*
• 1 capped 150cc container with exactly 40 grams (not 40cc) of mineral oil **
• 4 capped 150cc containers, empty
* One set of these 5 containers is used in the next investigation.
** The mineral oil containers are used again in Investigation 3.3.