It is something we find in the bathroom, but according to “Science Guy” Jason Lindsey with Hooked on Science the plunger isn’t just for unclogging the toilet.
STEP 1: Press the two plunger cups together.
STEP 2: Attempt to separate the plunger cups.
Suction occurs when there is a difference in air pressure. You created this difference when you pressed the two plunger cups together. By doing this, you forced out the air from inside each plunger cup reducing the pressure from within.
Go to hookedonscience.org for more experiments that might get you “Hooked on Science.”