Cool Science Club

Baking Powder Submarine


Build the famous diving sub of cereal box fame (except much healthier than eating a box of Sugar Pops to get it!)  Dives to the bottom of a water tank and then  surfaces by itself.  Then dives again and again!  Learn about fizzy chemical reactions, bubbles and bouancy!

  • Paring knife
  • flat bladed screwdriver (blade should be a little wider than a pencil)
  • pencil
  • big bowl of water


  • carrot (ready-to-eat baby carrot type)
  • several toothpicks
  • baking powder (not baking soda)


Step 1
Photo of all supplies needed for a sub.
Gather your supplies.

Step 2
Cut the carrot in half lengthwise and trim off the ends.

Step 3
Drill a hole allmost all the way through the carrot (from the flat side).

Step 4
Break toothpicks in half and insert as shown.

Here is the bottom of the sub. Observe the hole.

Step 5
The sub should just barely sink. Add or remove toothpicks till it barely sinks to the bottom.

Step 6
Fill the hole with baking powder.

Step 7
Pack the hole full and tight with the pencil.

Ready for launch!

Step 8
Place the sub in a bowl of room temperature water and watch it dive, surface and dive again!

Click below for more info about baking powder submarines (External Links):

A scientific description of the baking powder reaction from Clabber Girl Baking Powder

A page dedicated to cereal box submarines

Click here a for a video of this project (external link)

The Science:
The carrot, which naturally sinks in  water is made more bouyant by adding toothpicks.  When you place the carrot sub in the water it sinks to the bottom and the baking powder packed in the hole gets wet. A chemical reaction occurs, causing bubbles to form.  The bubbles build up in the hole in the bottom and make the sub more bouyant, causing it to rise to the surface.  When it hits the surface, it leans over and releases the bubbles reducing it's bouyancy and causing it to sink again.  The baking powder continues it's fizzy reaction, creating more bubbles, allowing the cycle to repeat several times.
Baking powder is a mixture of cornstarch plus powdered acids and bases.  When you add water, a fizzy chemical reaction occurs  that creates carbon dioxide gas.  These bubbles of gas make biscuits and cakes fluffy and light - and also make carrots float! 
More fun:
  • Stir the water for a moving sub
  • What happens with really cold water?  Hot water?
  • Why won't baking soda work?

Check out all the Cool Science projects at