Ask A Scientist Chemistry Archive

Question:
Okay.....I'm a student...and a sophomore in high school.....can you tell me
why an egg would go through a milk (glass) quart after a piece of paper is
added....to the quart.....the piece of paper is on fire.........then it
goes out as it gets sucked out of the top of the carton......well thanks...
I need total explanation......I know all the pressure....area.....equation
stuff...okay....help...???
 kevin parenti

Answer 1:
Kevin,
Here is my 'total' explanation.
If you have a bottle with a burning material in it, the burning material
is supplying energy and this creates a higher temeprature inside the
bottle. High temperatures are associated with FASTER molecular motion,
that is the molecules inside the bottle are moving around faster.
Associated with this faster molecular motion is an elevation of pressure
inside the bottle.  The pressure gets released though, assuming the
top of the bottle is open.  Were the bottle sealed, the pressure would
continue to increase.  In such a sealed system, though, the burning
material would soon stop burning as oxygen, necessary for fire, would
be depleted.
If you have a bottle with the top open and a burning material inside, the
pressure inside the bottle is increasing, and, if you place a shell-
less egg on top of the bottle, the fire will soon go out by oxygen
depletion. ASSUMING the egg effectively seals the bottle, the
cooling of the bottle (since the fire has gone out) will cause a
pressure DROP inside the bottle.  This low pressure is another name
for a vacuum.  Again, assuming the egg is effectively plugging the
hole, the vacuum created by the cooling bottle will pull the egg
into the bottle. If, however, there are 'leaks' around the edges of the
egg in relation to the bottle opening, air will be sucked back into
the bottle instead.  See the next note for a home experiment you can try.
 
Ric     Thanks for using NEWTON!
 
Answer 2:
     If you have any rubbermaid type food storage containers you
can duplicate an experiment I discovered during a recent forage
to the kitchen.   :)
 
     While preparing dinner one night, I was 'nuking' some
vegetables in a microwave in a rubbermaid container.  I had the
cover on the container, not on firmly, just set loosely on top
to avoid splashing from the cooking vegetables.  When the timer
went off, I removed the container from the microwave, but I
did not remove the cover which was still loosely setting on top.
As the material inside the container began to cool, the lower
pressure created by this began to draw air back into the container.
This quickly sealed the container top and in fact pulled the top
into the container in what appeared to be an amusing shape.
Naturally I had a bit of a time trying to remove the now inverted
lid from the container.  Can you explain what caused this to occur?
 
By the way, if you do try this at home, please be careful when handling
hot containers and the microwave.  As your parents to help you, and
best not to try to open the container fully until the contents are
cool enough so you dont get burned.  Let me know how you do!!   :)
 
Ric     Thanks for using NEWTON!