Lets Sink it!

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SWBAT explain how adding weight to wood causes it to sink by attaching paper clips to a wood block and submerging it in water.

Big Idea

Kids will learn that a floating object can be caused to sink by adding weight to it.


10 minutes

To start this lesson, I have the kids sit on the floor by calling one table at a time to sit like scientists. I ask them to think back to when we did our sink and float lesson. To do this, I have the kids talk to their floor partner about what they remember. We review the poster we made of things that sink and things that float.

I ask the kids to think about a block of wood; I show them a sample of the blocks they'll be using. I then ask them to imagine what they think will happen if we place a block like that one in a container of water. I have them tell their floor partner what they think will happen.

I pull 3 random name sticks from a name stick can and have them share their thoughts. They are encouraged to share their partner's thoughts as well. The kids share that they think the wood will float because all the wood objects that we placed in the water in the other lesson floated.

This section gets the kids thinking about the properties of materials, especially wood. I tell them that today they will try to get wood to sink.


10 minutes

The kids remain seated on the floor watching a 80 second video that reminds them of our sink and float experiment using a variety of objects.

As the kids are watching this short video, I place a one quart clear container of water on each table along with a supply bag that has one wooden block, a box of large paper clips and a rubber band.

I return to the class, which is still seated on the floor, and give them the following instructions:

  • hands in your lap until you're asked to touch the supplies
  • everyone will work respectfully and take turns
  • the water WILL remain in the container, so be careful!

I then explain the steps that they will take throughout the experiment:

  1. table leaders will be asked to take the supplies out of the bag
  2. the person sitting next to the table leader will wrap the rubber band onto the block two times (I demonstrate)
  3. the next person will place one paper clip under the rubber band
  4. the last person will place the block with the paper clip in the water
  5. you will go around the table adding paper clips, ONE per person, until the block is covered in water

I then dismiss the teams one at a time to go sit down at the tables with their hands in their laps.

I guide them through each step as noted above. Step 5 is repeated as many times as is necessary to submerge the blocks.


10 minutes

To explain what the kids have experienced, I have them sit on the floor by calling one table at a time. They are instructed to leave all experiment materials sitting at their table for later clean up.

I have the kids think quietly to themselves for 30 seconds about why they think the wood blocks sank in the water once enough paper clips were added. After providing them silent think time, I have them share their thoughts with their floor partner. I then call on four random students to share what they talked about by pulling name sticks from a name stick can. I do this because the kids are excited about science concepts and they all want to be heard. This model conserves class time.

After the kids have shared their ideas, I explain to them the concept of adding weight to a floating object to cause it to sink, which is it causes the object to become more dense, therefore causing it to sink.

I do it in this order because I want the kids to come to their own conclusions based on their experiences and evidence. I want them to connect ideas and concepts to decide what might be a plausible explanation before I provide them with the known answer.

The kids may not fully comprehend, but at a kinder level they understand that adding weight to a floating object causes it to sink and that is all that is expected of them at this age.


10 minutes

I have the kids remain on the floor while the table leaders come up and get the science journals for everyone at their table. They take them back and set them at each student's place. The table leaders return to the floor.

I then demonstrate on chart paper the expectations for the students' science journal entry. They are as follows:

  • detailed picture of experiment
  • minimum of two sentences
  • use of data collected from the experiment

As the kids work in their journals, I roam the room and individually ask the kids to explain to me what they are drawing and writing about.

As the kids are working in their journals, I roam the room and ask kids to explain to me what they are drawing and what they learned from the experiment. I use this time as an opportunity to clarify any misconceptions.

When the kids are finished, I have them come to the floor. The kids share their journal entries with their floor partners and explain to them what they've written. Each person in the pairs gets 30 seconds to talk; I set a timer each time. I tell them that the smaller student talks first.

I have them talk to their floor partners so they can learn from each other. They all may have relatively the same idea(s) recorded in their journals, but the oral explanations may vary. Partners are set by me. I choose students who are no more than two levels apart, e.g. high with med-low achievers, med-low with low.


5 minutes

To close and extend this lesson, I ask the kids to think about how they could sink the following by having them think silently for 20 seconds followed by sharing their idea(s) with their floor partner. I then choose 4 random students to share their discussions with the whole class. I do this by pulling name sticks from a name stick can. In this way, every child has an opportunity to share their idea(s), but class time is not taken up by having everyone share with the whole group.

We discuss each item ONE at a time:

  • balloon
  • feather
  • empty plastic bottle

I record their ideas on a board and encourage the kids to try experimenting with these things with their families and to draw and write about it. If they bring something back to share with the class, I will reward them with a special treat.