Students will be able to weigh 3 objects using standard units.

Students measured objects in non-standard units in a previous lesson and were surprised by various results. This lesson will help them identify the importance of precision in their investigations.

5 minutes

In yesterday's lesson, "The Weight of the Matter", the students used paperclips to weigh three different objects. At the end of the lesson, the children recognized that the measurements between groups were not the same.

Our question today is, **"What could cause these measurements to be so different?"**

I will give the students time to review what their thinking was the day before and ask them if they have any new ideas. Following their sharing, I will show them two of the material trays used in the previous lesson. We will look at each of the objects on the tray and notice that they are all exactly the same…until we get to the paperclips.

On one of the trays are small clips, and the second tray contains large clips. As I place these on the board, I will ask the students to discuss how this variable can create different measurements.

10 minutes

Next, I will introduce the students to gram weights. These weights are in 1, 5, 10, and 20 intervals. I explain that the students should try to figure out how to use these to re-weigh the same objects. When all groups are done, we will come together and compare the results.

While introducing the grams, you may want to explain a bit about how the metric system works and why scientists use the metric system, all over the world.

20 minutes

While students explore and investigate the object's weights, I will listen in. This is the part when we get to really teach. I like approaching a group and trying to figure out where to go with the information they are giving me through my observations.

As this group worked, they were trying to be so precise. While we were talking, they solved their problem together. They were also careful in how they used the measurement tool, and made an effort to find ways to place the grams in the cup without causing too much motion.

This attention to variables and precision is just as important of a skill at this age as the content of the activity.

This group noticed a relationship between the weight of their paperclips and the grams. This was a wonderful opportunity to discuss the mathematical relationship that they stumbled upon and have them work through it.

15 minutes

The closing of this lesson is the key to the sessions's success. This is when the students have to analyze data and make sense of it as a group.

When the students gather, we will place each team's data on the board, just as we did yesterday. I will repost the data from the day before as well. Then, I will ask the student's to discuss what they think, were the grams or paperclips more helpful? Which unit should be used in science? When would we ever use a nonstandard unit?

This girl did a great job in discussing how a paperclip is not a good measurement "tool" because it can be different each time.

In this conversation, the students were able to point out that there are even more variables, even when we all used standard units.