In their last investigations, students experimented with nonstandard units of meaure — paper clips, washers, and counting bears. In this investigation they explore — perhaps for the first time — an important unit of weight in the metric system: the gram.

Students weigh a variety of familiar objects in terms of grams and place those objects on the weight line. They then study the distribution of objects on the weight line, comparing size and weight. By the end of the investigation, students will be thinking of objects in terms of their gram weight. They will also be noticing that size and weight do not always correspond.

Learning Goals

• to use grams as a standard unit for measuring the weight of objects
• to think about the relationship between size and weight

Sequence of experiences
1. Ask the question	All Class	10 Mins
2. Weigh selected objects	Small Groups	15 Mins
3. Place the objects on the weight line	All Class	10 Mins
4. Make meaning	All Class	10 Mins

Materials and Preparation

For the class:

• Post the investigation question in a place where all students can see it.
• The plastic weight line — If your weight line has been left in view since the last class, make sure the students can get to it. If not, place the weight line in an easily accessible place.
• 1 gram weight set
• 1 index card labeled “Grams”
• 1 object weighing approximately 1 pound (450 grams)
• 1 object for each student to weigh from the following:
  Objects from the kit:
  

  • plastic spoon
  • metal spoon
  • counting bear
  • weight line

  • wooden spoon
  • key
  • large steel washer
  • rubber eraser
  Suggested objects from the classroom:
  

  • roll of masking tape
  • scissors
  • baseball hat
  • 3 pencils (different lengths)
  • student notebook

  • 2 different crayons
  • roll of clear tape
  • felt tip pen
  • pen
  • stapler
  • large binder clip

 
For each group:

• 2 pan balances
• 1 gram weight set

For each student:

• 1 gram weight
• 1 large paper clip