Applied Science - Physics (6B)
Post Lab

  • Investigating fluids in motion.
  • Demonstrating how air moves because of changing pressure.


  • expand
  • pressure
  • boiled egg
  • paper
  • match
  • bottle with an opening a little smaller than the diameter of the egg

Students use air pressure to "suck" an egg into a bottle.


The atmosphere is mainly composed of the gases oxygen, nitrogen, and carbon dioxide. Air molecules are constantly in motion, bumping into each other with a certain force. When air is heated, the molecules move faster and hit each other with a greater force, hence the air expands. The weight that the air exerts is called atmospheric pressure. Atmospheric pressure decreases the higher you go up in elevation. This is why some people might feel more tired at the top of the mountain than at sea level. Oxygen is less abundant the further you go from the surface of the Earth.


  1. You may want to go over the LAB materials to make sure students observed this motion of fluid. Many students will want to play with the materials and may prevent going into detail on each of the items. Use this post lab to complete the material. If you have completed the lab we suggest that you demonstrate other "fun" examples of fluids in motion. The case of the "dieting egg" can illustrate how pressure not only moves objects, but can actually force objects through an opening.
  2. You may want to do this experiment with your students and then challenge them to repeat it. Remind students to do this experiment with an adult present.
  3. You will need a peeled boiled egg, a bottle with an opening just large enough to prevent the egg from falling through, a small piece of paper and a match. Set fire to a small piece of paper. Place the paper into the bottle and quickly place the egg on top of the bottle. The egg will plop into the bottle!
  4. The fire heated the air inside the bottle causing the air to expand and with some of the air molecules escaping from the top. With less air in the bottle (decreased pressure) than the outside (greater pressure) the egg is pushed into the bottle. Students cannot see the motion of the air, but it is occurring.

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