Lesson 6

The purpose of this lesson is for students to learn to measure and estimate the weight of objects in grams or kilograms.

In previous grades, students learned that weight is a measurable attribute and directly compared the weights of two objects. In this lesson, students learn that weight is a measure of how heavy something is. They are introduced to grams and kilograms as metric units for measuring weight. Students hold objects of different numbers of grams and kilograms to familiarize themselves with the units before estimating the weight of objects in those units. Since the distinction between mass and weight is beyond what students need to learn, the term “weight” is used throughout the unit.

To build a sense of weight measurements and an intuition for comparison, it is extremely helpful for students to have firsthand experience of holding different weights. To make that possible, some new materials and preparation are required for this lesson.

• Create a set of metric weights (1 kilogram, 2 kilograms, 1 gram, 10 grams, 100 grams). Weights can be made by filling bags with the following quantities of objects:
  • for 1 kilogram: 1,000 jumbo paper clips or a 1 liter bottle filled with water
  • for 1 gram: 1 large paper clip
• Create a poster with the labels “less than 1 gram,” “between 1 gram and 100 grams,” “between 100 grams and 1 kilogram,” and “over 1 kilogram” for the synthesis.
• If possible, gather scales (analog and digital), primary balances, and any other available weight measurement tools for the synthesis of Estimate Weight activity. Prepare enough tools for each group of students to have one, or prepare one for a whole-class weighing demonstration.

What ideas about liquid volume do students have from their everyday lives? How did these ideas influence their work in this lesson?