The purpose of this activity is for students to learn that grams and kilograms are standard units for measuring weight. Students are introduced to the units using common objects as benchmarks. For each benchmark, students hold an object of some number of grams or kilograms and think of an example of an object that has about the same weight. Then students look for items in the room that are in specific weight ranges. 

If time permits and if a scale or a balance is available, give students an opportunity during the Activity Synthesis to confirm the weights of the objects that they estimated. Depending on the number of weight measurement tools available, arrange for a whole-class weighing demonstration with the objects students chose, or arrange for students to weigh their chosen objects in groups, taking turns with each type of available tool.

• Select students to share 1–2 examples from each column.
• Record responses on the poster labeled with the different categories.
• To familiarize students with the available weight measurement tools, display them for all to see, and consider asking:
  • “What do you notice? What do you wonder?”
  • “How do we read the scale? What if the scale is in between two numbers?”
  • “How do we know when a balance shows that objects have the same weight?”
• If possible, allow students to use a scale or a balance to confirm the weight of some of the listed objects.
• If multiple scales are available, allow students to weigh their objects in groups. If only one scale is available, demonstrate it for the class.

The purpose of this activity is for students to use what they’ve learned about grams and kilograms to estimate the weights of some common pets. Students should rely on the experiences they have had in previous activities to explain why the estimates they choose are reasonable. In the Activity Synthesis, students consider when it might be helpful to estimate a weight rather than measure the exact weight.

• Invite 3–4 students to share their response for one of the pets, including how they determined the amount would be a reasonable estimate.