Day One:
Experiment #1
The egg and the milk bottle
Materials:
1. One hard-boiled egg.
2. One empty glass milk bottle
Procedure:
1. Peel the shell off from the hard-boiled egg and place the egg on the mouth of the milk bottle.
2. Ask: "What will happen if I put a burning piece of paper in the bottle and place the egg back on the bottle?" (anticipated answer:'egg might jump off', 'fire will go out', 'the bottom of the egg will get black', 'the bottle might crack', etc.)
3. Burn a small piece of paper, lift the egg up, put the burning piece of paper in the bottle and place the egg immediately back on the bottle's mouth (egg will be sucked into the bottle).
4. Ask: How can we get the egg out of the bottle without cutting it up?
5. To get the egg out of the bottle whole: invert the bottle and let the egg fall in the bottle neck, blow a short spurt of air up into the inverted bottle and catch the falling egg.
Explanation:
The burning paper is heating the air in the bottle and expanding it, and this is why the egg was vibrating before it was sucked into the bottle. Some of the air slipped under the egg out of the bottle and thus there was less air preessure in the bottle. An added cause for decreasingthe pressure inside the bottle is, that the burning of the paper took away the oxygen of the remaining air4, turning it into CO2 and water vapor. The latter condensed against the cold bottle. Another way to get the egg out is, to warm the bottle while the egg sits in the bottle neck.
Experiment #2
The Cups and the Balloon
Materials:
1. An uniflated round balloon.
2. Two small plastic or glass cups (with a smooth rim).
Procedure:
1. Blow up the balloon about one-third way.
2. Tell the students that you will hold the two cups against the sides of the balloon and blow it further up.
3. Hold one cup in each hand, hold the cups against opposite sides of the balloon (while the balloon is in the mouth) and blow further (unitl about twice the size).
4. Let go of the two cups (they will stick to the balloon; if not, moisten the cup rims) and hold the balloon in one hand by the mouth.
5. Show the students that the cups are not glued to the balloon by releasing the air slowly out of the balloon (the cups will fall off as the balloon gets smaller).
Explanation:
Because of the increase in curvature or actually a flattening of it from A to B, the volume in the cups increased, thus causing the pressure to decrease. The air pressure inside the balloon had nothing to do with the sticking of the cups to the balloon.