Burning vs Heating:

Schaumburg, Carl Von Steuben High School

Objectives: To teach the concepts of chemical and physical changes, and the differences between burning and heating Apparatus Needed: Burner, matches, wood splints, thin glass rods, Mg ribbon, candles, lead strips, steel wool, evaporating dish, forceps, flask, fire proof trivet, lighter fluid Recommended Strategy: First hold a wooden splint in a burner or torch flame. Remove the splint from the flame and ask the students what is happening. Responses might include: smoke, wood is getting smaller, turning black, etc. Hold an evaporating dish in the flame and note the soot on the bottom of the dish. The point is to have the class realize that something is happening to the wood, new substances are being formed, and that the process is named burning. Next hold a piece of glass tubing or rod in the flame. Is this heating the same? Does the "flame" remain when the glass is removed from the torch or burner flame? Is the glass getting smaller? Is it turning black, etc? If the glass bends, simply straighten it, and point out that this kind of change is not permanent. Does this "flame" produce the same soot as noticed with the wood? Is this another example of burning or something different? Now would be a good time to introduce and define chemical and physical changes. Continue the process with heating of a candle halfway down the length of the candle (with a flame on the slant) and also in the
usual place at the wick. Go through the same ideas introduced in the
previous sections and determine if the change is chemical or physical,
heating or burning. Other materials that could be heated are: Mg
ribbon (be careful of the intense light), a coat hanger wire (after
removing the paint), a strip of lead (heat over the trivet), steel
wool, and an icicle. Each time go through the same determination of
the type of heating.
To complete the lesson, make water appear to burn. Before class,
add a few drops of lighter fluid to a flask. Swirl around to
distribute the liquid to the glass walls. Discard the excess so that
the flask appears empty. Ask if water burns. Add water to the flask
directly from the faucet, filling to the top of the flask. The lighter
fluid will float to the top and can be made to burn. End the lesson
just at the bell and leave the "burning" water as the conclusion.
Explain next time.

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