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Fire Science Strikes!

19 Apr

 The fascination with fire and candles seems to have been sparked again over the last couple of days.  Our ‘flicker’ lighter ran out of fluid so we’re on to discovering matches in the back of the pen drawer to light candles and blow them out.  We’ve talked about and researched fire at length before and even experimented with hypothesizing outcomes and then burning various natural materials.

After figuring out how a match ‘works’ (below), the kids (who were eating lunch while doing all of this) wondered laughingly what would happen if they set fire to each of their food items.  Here’s what happened:

Cheddar cheese- Hypothesis– Sadie- it will catch fire!  Elijah- it will turn it to fondue!  Outcome– it browned and dripped onto the plate.

Grape tomato- Hypothesis– Sadie- it will catch fire!  Elijah- it will explode and tomato juice will go everywhere.  Outcome- it shriveled and blackened.

Hard pepperoni- Hypothesis– Sadie- it will catch fire!  Elijah- it will cook or burn.  Outcome– it decreased in size and blackened.

The introduction of the use of matches brought a new curiousity that was satisfied by this perfect URL (found by Googling the question, “How does a match work?”). 

How does a match work?

(Lansing State Journal, Sept. 25 1997)


 

Although you may not know it, striking a match starts a chemical reaction. There are two types of matches: safety matches and “strike anywhere” matches. A safety match can only light when someone strikes it against the striking surface on the side of the match box. A “strike anywhere” match can be lit by striking the match on anything solid. A “striking surface” is made of sand, powdered glass, and a chemical called “red phosphorus”. The head of a safety match is made of sulfur, glass powder, and an oxidizing agent. An oxidizing agent is a chemical that takes electrons from another chemical. When a chemical loses electrons we say it has been oxidized. An oxidizing agent is necessary to keep a flame lit. Oxygen gas is a common oxidizing agent. A simple test for oxygen is to hold a red hot (no flame) piece of wood in a tube of gas that might be oxygen. In oxygen things will burn much faster than in air, and the wood will burst into flame.

When a match is struck on the striking surface of its box, the friction caused by the glass powder rubbing together produces enough heat to turn a very small amount of the red phosphorus into white phosphorus, which catches fire in air. This small amount of heat is enough to start a chemical reaction that uses the oxidizing agent to produce oxygen gas. The heat and oxygen gas then cause the sulfur to burst into flame, which then catches the wood of the match to catch on fire.

A “strike anywhere” match works in a similar way, but instead of phosphorus being on a striking surface, it is added to the head of the match. You can tell the difference between the two types of matches by looking at the colors of the match heads. A safety head is only one color, but a “strike anywhere” match is two colors: one for the phosphorus, and one for the oxidizing agent.

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Posted by on April 19, 2010 in Uncategorized

 

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