## Lesson: Measuring and Comparing Weight and CapacityIntroducing the Concept

Developing children's understanding of measurement is an ongoing task. Children are becoming familiar with the units that are used to measure different attributes of items. In this lesson they will learn how to compare items by weight in pounds and by mass in kilograms.

Materials: pan balance, at least one 1-pound weight and one 1-kilogram mass, an inflated balloon or beach ball, a tennis ball

Preparation: Gather items that weigh approximately pound, 1 pounds, and 3 pounds.

Prerequisite Skills and Concepts: none

• Say: We have learned how to measure the length and height of different objects. Today we are going to talk about measuring weight.
Hold up two items and ask the children to predict which is heavier.
• Ask: How can we find out which one is heavier?
Answers will vary. Children may say that you could hold both items to see which is heavier. Lead children to see that you can use a balance to find which is heavier.
• Ask: If I put one item on each side of the scale, how will I know which one is heavier and which one is lighter?
Children may say that the side of the scale with the heavier object will go down and the side with the lighter object will go up. Place the items on the scale.
Compare several other items in this manner, each time asking the children to predict which is heavier and which is lighter. Finally, hold up the beach ball or balloon and the tennis ball. Ask for predictions of which will be heavier. Discuss whether or not the size of an object affects its weight. Then use the balance to see which is heavier.
• Say: The tennis ball is heavier than the beach ball, even though the beach ball is bigger. So size alone doesn't determine how much something weighs. Something big can weigh less than something small. Now, instead of comparing objects to one another, we will compare them to a unit of measure called a pound. We will look at several items and decide if each one weighs more or less than a pound. This is a 1-pound weight.
Pass the weight around the class and have children feel how heavy it is. Then hold up an object that weighs about pound.
• Ask: Does this object weigh more than one pound?
Elicit opinions from children.
• Ask: How can we tell if this object weighs more than a pound?
Children may suggest that they could hold it and compare its weight to the 1-pound weight, or they could use the pan balance to weigh it.
Put the 1-pound weight on one side of the balance and the object on the other.
• Ask: Now who can tell if this object weighs more than a pound?
Children should say that it weighs less than a pound, because the side of the balance with the 1-pound weight is lower than the side with the object.
Repeat this activity using the objects that weigh more than one pound.
• Say: Now let's compare objects to another unit of measurement called a kilogram. This is a 1-kilogram mass.
Pass the 1-kilogram mass around the class and have children feel it. Then hold up an object that weighs about 3 pounds.
• Ask: Is this object more than one kilogram?
Elicit opinions from children.
• Ask: How can we tell if this object is more than one kilogram?
Children may suggest that they could hold it and compare it to the 1-kilogram mass, or they could use the balance to compare it.
Put the 1-kilogram mass on one side of the balance and the 3-pound object on the other side.
• Ask: Now who can tell if this is more than one kilogram?
Children may say that it is greater than 1 kilogram, because the side of the balance with the object is lower than the side with the 1-kilogram mass.
Repeat this activity, using the objects that have less mass than a kilogram.