## Kindergarten Mathematics Module 3, Topic C

In Topics A and B, students compared length and height, and now, in Topic C, they compare the weight of objects, progressing from informal comparisons of objects (comparing the weight of a book to that of a pencil by picking them up) to using balance scales when greater precision is necessary or desired (comparing the weight of a pencil to a marker by using a scale). In Lesson 8, students compare the weight of a book to the weight of an eraser and other objects they find. Students then use the weight of the book as a benchmark and find other objects to compare with the weight of the book. “This eraser is lighter than my book. The bag of blocks is heavier than my book.” In Lesson 9, students use a balance scale as a tool to compare the weights of objects that are approximately the same, and thus more difficult to compare. For example, “My pencil is lighter than this marker.” In Lesson 10, the measurement becomes more precise as a set of pennies is used to directly compare the weight of objects. Students use a balance to determine that the pencil weighs the same as a set of 5 pennies. The marker weighs the same as a set of 9 pennies. The students are comparing one object to another, a set and a solid object. They stay within kindergarten standards by not comparing the number of pennies each weighs, instead simply enjoying the exploration of finding the set of pennies that weighs as much as an object. In Lesson 11, students observe conservation of weight, for example, by placing two balls of clay of equal weight on either side of their balance scale. They break one of the balls into two smaller balls and observe the two sides of the scale still balance. They then break the single ball into three smaller balls and observe the same thing. The lesson continues with a sequence leading back to the two balls once again balancing after all the permutations.