Trying Again to Save the Gingerbread! - An Continuation of an Assessment Task on Density
Lesson 11 of 11
Objective: Students will be able to demonstrate their knowledge of density by making revisions to a model.
This lesson is a continuation of Save the Gingerbread, a performance assessment on density. The students had the opportunity to build a raft to save the gingerbread boy so he could hop on the raft to cross the river instead of riding on the fox's tail. The students tested their rafts and during the lesson, we discussed improvements that could be made to the rafts. The students are getting the opportunity to make these improvements in this lesson. This lesson supports the NGSS Engineering and Design Standard. Not only were the students given the challenge to design a raft, they are now being challenged to make improvements upon this raft.
To begin the lesson, I ask the students some questions.
What did our successful rafts look like yesterday?
What were problems that some of our rafts had yesterday?
I hope that you thought about how some of the problems could be addressed and how you could make improvements based on what you know about density and the successful rafts. I want you to move into your work groups and get ready to make improvements to your raft.
You will need the rafts from the previous day's lesson. In addition, you will need the following:
Materials Needed for Work Station (one station shared by entire class)
- construction paper
- laminated paper
- small pieces of sponge
- small plastic zipper bag (the kind used for crafts and jewelry)
- masking tape
- bubble wrap
Materials Needed for Each Work Group
- one pan of water
- 1 gingerbread cookie or a construction paper gingerbread
I say to the students, Now, I want you to get together with your work group and discuss the improvements that you are going to make on your raft. Feel free to come up to the material's table and get the resources you need to create your raft.
The students begin working. I assist as needed by tearing masking tape, etc., but I try to stay pretty "hands-off". I want this to be their work. The students finish their raft and prepare for the final test.
Twenty minutes are up and now it is time to test the rafts. We gather together at one table for the testing. I have one student from each group in front of their pan of water, holding the raft and we place the gingerbread in it. Before the raft is placed in the water, I have the students describe the improvements they made to their raft. We count off and the students place the rafts in the water. I have the timer set for one minute and we watch to see whether the rafts float or sink. When a minute is up, we check the condition of the gingerbread in the raft.
The students made some amazing improvements to their raft. This video shows how the students engineered a straw to hold the raft out of the water. Their raft tilted to one side and they solved the problem with the straws.
After everyone has tested their raft, we move into the lesson closing.
To wrap up our learning, we discuss how the changes in the rafts improved the rafts' performance. I want the discussion to focus on their knowledge of density, but also to impress upon them the engineering work they just completed.
- I ask the students these questions:
- How come the rafts were more successful this time?
- What did you do to improve the rafts?
- Did the materials that you used make a difference? Why?
- What did having a second chance to do the function of your raft? Why?
Engineers are people who design or create things. They don't just magically come up with the correct design the first time, they often have to try over and over to find the perfect design. Today you were engineers. You made something and then you learned what its strengths and weaknesses were and then you improved upon it. That's exactly what an engineer does!! Great work!