Sink or Float?
Word of the day: float
“Some things swim and some things sink. Let's be scientists and guess first.”
Grab
- a big bowl or the bathtub
- a towel
- 6 to 10 things: apple, grape, coin, cork, spoon, LEGO, crayon, toy boat, orange (with and without peel)
Do
- Before each item goes in, they guess: sink or float? Put it in a 'sink' pile or 'float' pile first.
- Drop it in. Was the guess right?
- Save the surprise for last: an orange floats. Peel it and try again. It sinks.
- Roll a ball of foil and it sinks; flatten it into a little boat and it floats.
The big moment
The orange floats. Peel it in front of them. It sinks.
Ask (guess first, then try)
- Do big things always sink?
- Why did the orange float with its coat on?
What's going on (for you)
Whether something floats depends on how heavy it is for its size (density). Orange peel is full of tiny air pockets, like a life jacket. The same foil floats as a boat because the shape holds lots of air and pushes aside lots of water.
If they want more
Boat challenge: how many coins can the foil boat hold before it sinks?
Look it up
Wikipedia: Buoyancy PhET simulation