Boiling water in a paper cup

We all know that pa­per ig­nites eas­i­ly. But how about an ex­per­i­ment where pa­per doesn't burn, and you can eas­i­ly boil wa­ter in it?

Safe­ty pre­cau­tions

Ob­serve safe­ty rules when work­ing with fire.

Equip­ment

• 2 pa­per cups;
• stove;
• sol­id fuel;
• 200 mL wa­ter;
• tea bag.

Step-by-step in­struc­tions

Place a pa­per cup on a stove and ig­nite some sol­id fuel un­der­neath it. Note how quick­ly the cup burns. Re­peat the ex­per­i­ment with an­oth­er cup, but this time fill the cup with wa­ter. Note that the pa­per cup doesn't burn, but the wa­ter in it boils. You can even brew tea with it!

Process de­scrip­tion

Yes, pa­per ig­nites eas­i­ly, but in re­al­i­ty, it ig­nites be­cause it reach­es its so-called ig­ni­tion tem­per­a­ture. Wa­ter’s rel­a­tive­ly high ther­mal con­duc­tiv­i­ty pro­vides for the rapid dis­tri­bu­tion of ther­mal en­er­gy through­out its vol­ume. Ul­ti­mate­ly, we’re not just heat­ing the cup's sur­face, but also all the wa­ter in it at once, which pre­vents the pa­per from reach­ing its ig­ni­tion tem­per­a­ture. Such a “heat guard” will work un­til the wa­ter boils away.