Make a Spitting Bottle
In this science experiment, kids explore gravity and water pressure while making a "magical" spitting bottle.
In this activity, the forces of gravity and air pressure act on the water inside the bottle. Gravity pulls downward on the water inside the bottle, but this force is the same whether or not the cap is on the bottle, so it doesn't control the "spitting." It's changes in air pressure make the water squirt out: When the cap is loosened, air can get inside the bottle, and the air pressure begins to force the water down and out. When the cap is tightened, the air pressure stabilizes and the water stops squirting.
- Plastic water bottle with water inside, at room temperature - 1 per student
- Dark permanent ink markers
- Decorating items (googlie eyes, glue dots, eye stickers, or similar
- Awl or sharp knife - 1 total
- Tub, bowl, sink or similar
Be sure the bottle is at room temperature. If it is cold, it will "sweat" and you won't be able to decorate.
Peel off any labels from the bottle.
Draw a mouth about 2 inches from the base of the bottle.
ADULT SUPERVISION: Poke a hole in the middle of the mouth using an awl, sharp knife tip or similar.
Finish decorating the bottle with eyes, a nose, hair -- whatever!
Now you are ready to experiment. Holding the bottle over something that can contain the pouring water, slowly unscrew the cap. Water will “magically” spit out of the mouth. Now screw the cap back on -- the bottle stops spitting! Repeat until the water is gone; refill as many times as you'd like. (Note that any pressure on the sides of the bottle will make a little water come out, so to create the illusion of a magically spitting bottle, be careful not to squeeze the sides.)