October 13, 2015 by libraryheather
Target Age Range: Grades 1-3
Program Length: 60 minutes
Explore the science of floating and sinking with demos and activities.
2 1-cup measuring cups
1 cup dried beans
1 cup mini marshmallows
1 small rubber ball (up to you whether it is full of air or solid like a super ball)
1 piece of chalk
1 clay square
1 wood square of roughly the same size as clay square
1 ping pong ball
1 golf ball
Pencils (1 per participant)
Sink or Float Prediction Sheets (1 per participant)
Clear shoebox-sized plastic storage containers for sink/float experimenting (1 per table of participants)–we got ours at the Dollar Tree, and have used them multiple times in programs
2 clear plastic containers or pitchers for sink/float demos
1 container table salt
6 rolls tin foil (or 1 box per table)–these can also be purchased at a dollar store
Pennies (we recommend ~50 per table)
Modeling clay (enough so that your participants can each make a small, cup-like boat)
A variety of sink/float items that can be used for boat building at each table (we used: LEGO bricks, cork circles, squares of styrofoam, circular scrub sponges, chalk, crayons, marbles, toothpicks, tape, and any remaining tin foil)
Multiple bath towels
Cost: $-$$ 0-100 (depending on what you have laying around that you can use!)
- Test out a few tin foil boat designs at home and see how many pennies they can hold. It’s very illuminating to see which kinds work best! It will help you troubleshoot this project with the kids.
- Put 1 cup of mini marshmallows in a 1-cup measuring cup.
- Put 1 cup of dried beans in a 1-cup measuring cup.
- Fill containers of water for demonstration purposes.
- Fill a shoebox-sized clear plastic container at least halfway with water (make 1 per table).
- Make a brick out of clay that is roughly the same size as the wood block you have.
- Print out the Sink or Float Prediction Sheets.
1. Settling in, welcome, introductions: 5 minutes
2. Explain density (be sure to include how everything is made up of molecules!) and how things float: 5 minutes
3. Read “What Floats in a Moat?” – Lynne Berry: ~5 minutes
4. Pass out Sink or Float Prediction Sheets for them to fill out, then demonstrate those objects sinking or floating: ~5 minutes
5. If something as light as a golf ball sank in water, how can something as heavy as a huge ship float? Explain how boats float: <5 minutes
7. Floating Egg Demonstration: 5 minutes
8. Make and test out small clay boats: 10 minutes
9. Make and test out foil boats and other float/sink items: 15 minutes
Sink or Float Prediction Sheet
Special Instructions and Procedures:
- Explain Density:
Use the explanation from the Indianapolis Public Library’s Kids’ Blog to demonstrate the concept of density and mass. We used a cup of mini marshmallows and a cup of dried beans. The kids instantly grasped which one would be more dense. Mrs. Salsich’s Class Blog also has a good explanation of density.
- Explain Why Things Float:
We discussed the concept of buoyancy and water displacement here. There is a good explanation on SeaPearch.org, but you will want to break it down into simpler terms. This PDF from 21st CASP also has good explanations. The best way to figure out a simple explanation is to check out some easy reader sink/float books from the library and see what they say!
- Sink or Float Demonstration:
First, the children should use the Sink or Float Prediction Sheets to write in their predictions for each object–“S” for “Sink,” and “F” for “Float.” Once they’re done, hold up the first object and ask for a show of hands for who thinks it will sink, then who thinks it will float. Then, try out the object in a clear tub (or pitcher) of water. Repeat! The objects we used for this station were: a marble, a small rubber ball, a crayon, a piece of chalk, a clay block, a wood block (of same size as clay block), a ping pong ball, and a golf ball.
- Explain Why Boats Float:
The idea that boats can float, but something smaller and lighter (like a penny) will sink can be confusing. Use this excellent explanation from Science With Me to better understand the concept and lead a discussion about it.
- Sink/Float Fruit Demonstration:
It’s fun to ask kids for predictions on what will sink or float before you try out each item. The orange is so heavy, odds are they will think it’ll sink–so, be sure to explain why it can float! We did not peel the orange, but said that if we did, it would sink. Then, ask them to take a close look at the rinds of the lemon and lime and make a guess at if they will sink or float. Try it out, and then ask if anything would change if you removed the rinds. A great explanation of this phenomenon is here at Weird Science Kids.
- Floating Egg Demonstration:
Start out by predicting whether the egg will sink or float in regular water. Then stir a bunch of table salt into the water, dissolving as best you can. What will happen now? Use this egg-cellent explanation of this egg-speriment on Explorable.com.
- Clay Boats:
This idea came from this PDF from 21st CASP. First, we showed them how to quickly and easily shape a small boat out of clay, and asked whether it would sink or float and why (then we tested it). We reminded them of what we explained in the “why boats float” discussion. Then, they had a few minutes to try making their own small clay boats and test them out at their tables. Try to get them to make a floating shape without any weights first, but then offer up pennies to try to sink the boat (that’s the best part, after all!).
- Foil Boats, etc:
We said: “We want you to try to make many different kinds of boats that will stay afloat on the water. You might make a raft, which is just a flat piece of foil, or you could make a raft with edges on it (like a box top), you could make something that looks like a canoe, a rowboat (triangular in front), a round bowl, or something else. We also want you to try to see how many pennies you can put on it before the boat sinks! We have lots of other stuff that floats that you can try to make boats out of, too. This is what we’re doing for the rest of the program, so keep experimenting!”Resources Used:
SEDL.org: Afterschool Lesson Plan – Physical Science: Sink or Float?Unmuseum.org: Experiment With BuoyancyKids Activities Blog: Sinking ShipsThe Indianapolis Public Library Kids’ Blog: Density – Buoyancy
Science Bob: The Magic Ketchup Experiment!
What we would do differently:
The kids loved using LEGOs for their sink/float experiments (of course). We loved seeing them play with LEGOs in water. We did not love drying out the tiny nooks and crannies of a literal ton of LEGO bricks so that they did not turn moldy. That was time consuming and awful. So, we suggest you avoid this.
We only brought 1 big bathroom towel for cleaning up water that would inevitably get splashed all over the place. Mistake! We should’ve brought as many towels as humanly possible. At the end of the program, one kid proudly said, “Look, Mom! I got the MOST water on MY table!” Yep.
Adaptation for older/younger audience:
You could definitely do buoyancy with a younger audience–there is no limit to how much kids love playing with water. It would be fun to adapt this program into a more general, water-based STEAM Storytime with a couple sink/float stations. Insofar as an older audience, we did a boat building/racing program with 4th-6th graders that used some of these same scientific principles.