After a dinner party, the host performed the following...

Name: Problem 127, Chapter 6: Chemistry
Uploaded: 2020-08-03T17:27:02-08:00
Duration: 1 min 22 s
Channel: Susan Hallstrom
Description: After a dinner party, the host performed the following trick. First, he blew out one of the burning candles. He then quickly brought a lighted match to about 1 in above the wick. To everyone's surprise, the candle was relighted. Explain how the host was able to accomplish the task without touching the wick.

After a dinner party, the host performed the following trick. First, he blew out one of the burning candles. He then quickly brought a lighted match to about 1 in above the wick. To everyone's surprise, the candle was relighted. Explain how the host was able to accomplish the task without touching the wick.

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Key Concepts

Combustion

Combustion is the chemical process in which a fuel reacts with an oxidizer, typically oxygen, to produce heat, light, and combustion products. In the context of candle flames, the gradual vaporization of the wax and its subsequent ignition are central to sustaining the flame despite interruptions.

Wax Vaporization

When a candle burns, the heat from the flame melts the surrounding wax, which then vaporizes and acts as a fuel for the flame. Even after the flame is extinguished, the wick may remain hot enough to continue vaporizing wax, creating a pocket of flammable vapor near the wick.

Ignition and Flame Propagation

Ignition is the moment when a fuel and an oxidizer mixture reaches its ignition temperature and begins to burn. Flame propagation describes the way this burning spreads from a small ignition source to the surrounding area, which is key when an external flame ignites the vapor above a hot, previously lit wick.

Heat Transfer and Convection

Heat transfer, especially through convection, is the movement of thermal energy in fluids such as air. The residual heat in the candle’s wick and the surrounding air can help maintain a temperature that supports wax vaporization and assists in transferring heat from an external flame to ignite the vapor.

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