• a hard-boiled egg (peeled)
• a glass bottle with an opening slightly smaller than the egg
• long matches or a long lighter
• a candle or a strip of thick paper, such as newspaper or cardboard
What do you do: Ask the children to put the candle or piece of paper in the bottle and then light it for them. Then the children put the egg in the opening of the bottle. When the flame goes out, the egg should slowly sink into the bottle.
cool science: Children don’t push the egg into the bottle; he is sucked in by the air tightness. Air is made up of small particles, also called molecules. When the molecules are further apart, the air expands and the air density (the amount of particles in a given space) decreases. When the molecules get closer, the air thickens and the light density increases.
When you light the paper, the air molecules in the bottle heat up and move faster, expanding the air and decreasing its density. When the flame goes out, the air suddenly cools. Molecules slow down and move closer to each other, increasing air density and taking up less space. Normally, air would enter from outside the bottle to fill this space, but in this case, the egg is in the way! The air pressure outside the bottle now pushes the egg into the bottle.
(If you want to see even more magic, have the kids turn the bottle upside down and blow into the bottle, mouth all the way through the opening. If all goes well, the egg will fly away.)
Push a straw into a potato – no super power.
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