You have a glass jar. You pour in water with a pitcher until it is half filled. You then seal the jar with an air-tight lid. (The only other thing in the jar is regular air). Assuming that the water in the jar is not already boiling after attaching the air-tight lid, how do you make the water boil?

boiling: the state in which liquid water is rapidly changing to water vapor (ie, the water is accually bubbling, not just steaming)

For clarification, the water is plain distilled H20. It is not heavy water, water with impurities, etc...

You cannot transfer or use anything that transfers light, heat, magnetic, electric, or chemical energy into the jar. (and no, shaking the jar till the water friction causes the water to boil does not work)

You cannot open or break the glass jar.

The area in the jar cannot increase or decrease. (You can try but the jar will not shrink, grow, or deform in any way)

You cannot insert anything into the water.

You must be able to conduct this experiment with easily attainable equipment, chemicals, and other materials. (ie, no radioactive chemicals, no superpowers, no multi-million dollar scientific equipment, you get my drift...)

(Note: although it is hard for it to succeed, you can conduct this experiment at home and get the water to boil without any special equipment.)

S4TD is right, and the key is to have an extra tall jar with a metal (conductive) lid.

Boil water. As soon as it stops boiling (211 degrees) pour into jar and secure lid. Apply dry ice to the lid immediately, cooling the air and lowering its atmospheric pressure (a 4mm Hg drop in air pressure will lower the boiling point of water to 205 degrees). This should affect the air temp much faster than water temp as the glass in not very conductive. If done rapidly enough the boiling point will fall below the water temp causing the water to boil.

An easier way to observe this without the danger of trying to fly around the kitchen with scalding water, is to keep the half filled jar in a pot of water kept near boiling. Place regular ice on the lid and if that doesn't do it, raise the water temp. The water in the jar should boil before the water in the pot does.

 

Posted by Eric on 2005-12-07 03:46:09