BACKGROUND:

The weight of an object is another measurement used to describe an object.  In this lab students will be introduced to an elementary balance.  They will have the opportunity to weigh a variety of objects using the balance.

PROCEDURE:

1. Describe how to use an elementary balance. Identify the parts with students. Show the balance and describe how it works. Demonstrate that the pan with the heavier object will be lower. When two items are the same weight, the pans will be the same height. On the figure below, you put the item to be measured in one bucket and in the other bucket you put the measured weights. When the buckets are "even," that is how much the item weighs.
     
2. Hold up two objects and have students predict by raising their hands which object will be heavier. Then place each pair of objects on the balance and figure out which object is heavier. Help students identify the heavier object and review their predictions. Explain that you can find out just how heavy an object is by putting known weights on one of the pans until the two sides balance. Add up the weights to find out how heavy an object is. This is a good introduction to addition. Point out the weight of each of the weights as you add them up. Note that they are in grams.
     
3. Measure about five objects of various weights in front of the class. Ask for volunteers to add up weights and to tell the class the weight of the objects. This shows students that there is a reason for learning how to add.