Purpose of the discussion

It is unlikely that every group will have placed the cubes in the same order. The investigation question, How good are our senses at comparing the weights of cubes? asks students to connect the investigation question with data, take a position, and identify data that support the claim.

Provide a few minutes for students to review the data table.

Engage students in the focus question

Remind students of the investigation question.

Students will have a sense that “felt weight” is subjective–after all, there were disagreements about the orderings. They will also have seen that as the weights of objects get closer, it gets harder to distinguish them by touch. But they don’t know yet how accurate their orderings might be. They are not demonstrated facts; they are predictions.

• How can we know for sure?

Let them brainstorm some ideas. If time permits, show them the pan balance and ask if anyone knows what it is or how to use it. Let them know that in the next session they will use this instrument to check the weight order of the cubes.

Be sure to save the class table for the next investigation.