In Part 1 of this lesson students created 3 structures using different materials and a similar format. The structures are displayed around the room for students to see before we begin the testing of the towers.
I say to students, "before we begin testing our towers, I want you to take a couple of minutes and see what your classmates have made. You have seen some of the towers already, but take a few minutes to look at them. Think about which ones you think are the strongest." Students circulate around for 4 - 5 minutes before I ring the bell and have them return to their seats.
"Would anyone like to tell what they noticed as they looked at all of the towers in the room?"
I let students share their observations for a few minutes.
"I would like everyone to read the I Can statement with me, 'I can test my 3 towers and decide which material was the strongest.'
Today you will test each of your towers using dictionaries. You will place them carefully on the tower and count how many each tower can hold. You will record how many dictionaries the tower held on your journal page. You will work with one other group to test your towers."
I divide the students into working groups and let them bring their towers together for testing.
Before testing the towers I gather students together on the rug. I ask them to tell what they have noticed so far about the two towers that they built. I hope that they will think about the materials of the towers as well as the designs and any adaptations that they have made. After our discussion students are ready to test the towers. Explaining what we have noticed
Each group has 6 towers to test. I tell them, "now that you have your towers, you will begin by carefully placing one dictionary at a time on one of the towers. If the tower does not collapse, add a second dictionary. Continue until the tower collapses. Testing a Popsicle Stick TowerDo not count the dictionary that causes the tower to collapse. Count all of the other dictionaries and record that number on your journal page. I know your towers will be destroyed with this experiment but we are trying to decide which material is the strongest and I can't think of another way to let us figure this out. Remember that you will need to take turns testing your towers within your group."
I demonstrate testing the tower with one group's tower to show students how they would place and count the dictionaries. Testing The First Tower - a Demonstration
Students test the strength of each tower in their group. I circulate around watching how students test and their towers.
When all towers have been tested, I ask students to return to their desks with their journal pages. I ask them to number their towers 1,2 3 with 1 being the tower that held the most dictionaries and 3 held the least.
Now I ask for each pair to tell me which was their strongest tower. I put the words Newspaper, Popsicle Stick and Pasta on the board. I put up tally marks for each answer. We look to see which of the three had the most votes for strongest.
In a second chart on the board we tally up the weakest towers.
Finally we make a third chart of the middle towers.
I ask students to look back at their journals from Part 1 of this lesson where they predicted their own strongest to weakest tower. I tell them not to take out any pencils, but to just look and see how close their predictions were to their own findings or to the class findings.
"Does anyone want to share what they noticed from the three charts we have on the board, or from your own predictions and findings?"
I let students share their observations.
"Now I would like you to turn and talk to your tables about why the class might have found the strongest and weakest towers that they did. Can you think about the materials we used? Did the shape of the tower make a difference? Why do you think that ________ was stronger more often than __________? Share your ideas with your table mates." I circulate around to listen to student reasoning. I have given a conversation starter to get students thinking about the comparisons that I want them to do. I don't want them to just say, "My paper tower was the strongest." Instead I want them to think about the materials that we used, and the shapes of the towers they noticed. Is there a trend in materials overall. Is one material really stronger than another? We just found that ________ was the strongest most often. What does that imply about the material? The standard is to compare materials by their observable properties so I want to direct students to think about those properties and not just state which of theirs was strongest.
After about 5 minutes, or when everyone seems to have had a chance to share, I bring the group back together. I ask them to write in their own journals about why one of their towers might have been stronger than another. I am hoping that students will think about the materials used and why one material might be stronger than another.
"When we started building towers a few days ago, I talked to you about how scientists pick materials for a job based on the strength of the material. Do you think that we learned something about the strength of different materials this week? What did we find out with our experiment?"
I hope that students will talk about how one material is stronger than another, at least in the way they used it. If they do not refer to how they used the material, such as rolled up paper or bundled pasta instead of open sheets of paper or single pieces of pasta, I will ask if they think the way they used the material made a difference to its strength and how.
The materials we use do make a difference, and while real builders wouldn't use paper or pasta, students have been able to model how materials make a difference. I want them to realize that different materials are better for some jobs than others.