Why Did the Titanic Sink?-Applying the Concept of Density

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Objective

Students will be able to apply concepts of density by participating in a simulation activity.

Big Idea

The story of the Titanic is one that interests and captivates students. This lesson expands students understanding of density as they learn the "why" behind the Titanic sinking.

Opening

15 minutes

During our investigations on density, several students brought up the Titanic.  It was fun to witness their excitement about it.  Soon they were coming in and sharing different facts and information that they had learned.  Several checked out books from the library on the Titanic.  I needed to capitalize on this excitement, so I decided to come up with a lesson to help explain exactly why the Titanic sank.  It was fun to bring an interdisciplinary lesson into this unit, allowing the students to learn more about a historical event.  To help expand everyone's knowledge of the Titanic, I first read a book to the students.  I chose DK Reader, Titanic:  The Disaster that Shocked the World.  After we read the book, I wanted the students to focus on exactly why the Titanic sank, so I showed this video from YouTube to my class:

I ask the students to summarize why the Titanic sank.  The ability to summarize these ideas is an important scientific skill that also expands into their literacy learning.  I then tell the students that we are going to set our own Titanic sailing to see exactly what happened when the Titanic sank and the role that density played.

Simulation

15 minutes

For this simulation, you will need the following items for each group of students:

• A plastic ice cube tray (readily available at dollar stores)
• A flat tray filled with water
• A small cup for transferring water into the tray.
• Sinking the Titanic Prediction Sheet included as a PDF with this lesson

I distribute the recording sheet to the students and have them put their names on the top.  I say to the students, Today, we are going to sail our own Titanic.  We are going to do a simulation of how the Titanic sank.  A simulation shows us what happens during an event like the sinking of the Titanic.  You each have an ice cube tray.  That tray is your Titanic.  Why would an ice cube tray be a good representation of the Titanic?  (The students immediately talk about how the Titanic had several compartments inside of it, just like the ice cube tray).  That's right and now, we are going to see, how many of these compartments do we need to fill before the opposite side of the tray starts to lift out of the water, like the Titanic did.

I want you to take a look at the tray and make a prediction.  How many of the cells will need to be filled with water before the tray is out of the water and sitting on or above the surface of the water.  I have the students make their predictions.  The majority of the class predicts it will take 8-10 cells for the tray to lift from the water.

We start filling the tray.  I have the students fill one of the end cells and then we talk about what they observed (see video).  I ask them if they notice the tray tipping.  We continue with the cell next to the one they just filled.  The students are already starting to notice the tray tilting.  I circulate around the room and question the students about what is happening.  I want them to make a connection between the change in density in the cells because of the water replacing the air and the way the tray was sinking (see video).

It takes 5 cells filled with water for the end of the tray to lift to the surface.  The students are surprised.  They thought it would take much more.

Closing

10 minutes

To wrap up this lesson, I bring the students back together for a discussion of our simulation.  I ask them, Why did the ice cube tray dip into the water when we filled the cells?  The students express that it was because we added water.  I push them on this answer, I know it was the water that we added, but WHY did adding water cause the tray to dip?  The students start to share that it was the change it density.  We discuss as a group how water has a greater density than air.  When the air in the tray was replaced with water, it caused the tray to dip because the density became greater than the water.

This discussion prompts a student to ask a question, "How could that boat even float in the first place?  It had to be heavy."  What a great question!  And possibly, the focus of our next lesson.

To wrap up the lesson, I have the students do a Turn and Talk.  I say to the students, I want you to think about what you are going to tell your families about our simulation today.  What will you tell them we did?  What were our results?  Why did this happen?  Tell your partner and partners, make sure they don't forget anything.  I want you to be ready to tell your parents about our lesson.