Were humans able to boil water before we discovered how to make metal cookware? Absolutely. We’ve been boiling water in large, cup-shaped leaves for thousands of years! We’re able to pull this off because of a process called conduction, whereby heat is conducted away from the leaf and into the water. Do you think it’s possible to accomplish the same thing with a paper cup?
Is it possible to boil water in a paper cup? Why or why not?
- Several plain paper cups—most are coated with wax, but try to find the uncoated kind
- Several Styrofoam cups
- Stove burner
- Dry sand
- Large cabbage (optional)
- Turn the burner on medium heat.
- Fill a paper cup nearly to the brim with water.
- Using tongs, hold the cup of water about six inches above the heating element.
- Continue holding the cup over the heat. The paper or burn, or the water will boil. Record your observations. How can you explain what you saw happen?
- Fill another paper cup with sand.
- Repeat Steps 3 and 4 with the cup filled with sand and record your observations. Did the cup filled with sand produce a different result? If so, why?
- Fill the Styrofoam cup with water.
- Repeat Steps 3 and 4 with the Styrofoam cup and record your observations.
Extra: Repeat steps 3 and 4 with a large cabbage leaf filled with water. What happens?
Boiling water in a paper cup isn't as hard as it looks! If you held the cup at an appropriate distance from the flame, the water in the paper should have eventually boiled. The circular rim on the bottom may have burned. If your paper cup had a waxy coating, the wax may have melted off. The paper cup with sand will burn slightly. The Styrofoam cup will disintegrate.
Water draws heat away from a heat source through convection until it reaches its boiling point of 100 degrees Celsius. The temperature of the water remains fairly constant once it starts boiling—in fact, liquid water is incapable of getting hotter until it’s all turned to steam. Most types of paper burn at 233 degrees Celsius (or 451 degrees Fahrenheit). As the water heats up, it conducts heat away from the paper, preventing the paper from reaching that crucial temperature. Heat also continues escaping via the steam that’s created when water boils.
Sand also has the ability to conduct heat away from the paper, but it also has the potential to get a whole lot hotter than water. Eventually, the temperature of the sand climbs past 100 degrees Celsius, and once the temperature approaches 233 degrees Celsius, the paper will burn.
Styrofoam is an insulator, making it very poor at conducting heat. Heat can’t pass on through to the water, so the Styrofoam disintegrates.
Now go ahead and bet a friend or family member that you can boil water in a Styrofoam cup. Then do it! Here's how:
- Find a clean, dry rock small enough to fit in the cup without touching the sides.
- Fill the Styrofoam cup about two-thirds full of water.
- Using tongs, hold the rock directly over the flame until the rock glows orange.
- Using tongs, immerse the rock into the cup WITHOUT letting it touch the sides of the cup. The water in the cup will boil.