Objectives

• Students will learn how to use a gram balance.
• Students will learn that you cannot estimate the weight of rocks simply by looking at them.
• Students will estimate and compare the weights of different rocks to each other.
• Students will use gram balances to test their predictions.
• Students will practice finding heavier or lighter rocks through the use of a rock weight game.

Anticipatory Set

Materials

• Various rocks
• Butcher paper
• Labels for graph
• Gram balances, 1 or 2 per table
• Weigh less/more spinners

Procedure

1. Review the graph from the anticipatory set.
2. Pass around the rocks to let the children feel and predict which is larger by feeling them.
3. Use these rocks to model how to use a gram balance.
4. Discuss how you cannot predict how much something weighs simply by looking at it.
5. At their tables, children will find a partner to play the weighs less/more game with.
6. To play the game, one student chooses a rock from the collection on the table.
7. The second student spins the spinner. If it lands on more, the student finds a rock they think weighs more. If it lands on less, the student finds a rock they think weighs less.
8. Weigh the two rocks using the gram balance to see if the second student was correct. Repeat until time is up ~ 15-20 minutes.

Evaluation

1. Have the students already had practice using a gram balance? Are they following your instruction as you model its use?
2. Have the students internalized that you cannot estimate weigh solely by looking at it? If posed another pair of rocks, would they make assumptions simply by looking at them?
3. Are the students making logical and accurate predictions of comparison of weights of rocks by feeling them?
4. Are the students having trouble using the gram balances? Do they need further modeling and instruction with them?
5. During the rock weight game, are the students using the gram balances check their estimations and comparisons? Or are they simply judging by how heavy the rocks feel?