FACTORS AFFECTING APPARENT KINDLING TEMPERATURE
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Submitted by: F. B. Dutton, Michigan State University Checked by: Forty Michigan State University Traveling Science Teachers En1~on'sNOTE: Innumerable uariations of the following demonstration are frequently performed by teachers. I t i s suggested that these simple demonstrations contain more teaching opportunities than are commonly used. PREPARATION
Provide wood shavings, saw dust, and a short piece of a 2-in. X 4 i n . block of wood; magnesium powder, ribbon, and a short length of I-in. magnesium rod or similar mass; iron powder, steel wcol, and an iron rod or bar; fresh calcium turnings, and a calcium turning that has been exposed to air for some time; matches, Bunsen burner, tongs, and asbestos or Transite sheet to protect table top.
3. Repeat steps in (2) with iron bar, steel wool, and iron poader. 4. Attempt to ignite a calcium turning using tongs (a piece with clean surface can he ignited if the temperature can be raised to t,he kindling temperature rapidly). Repeat attempt with calcium turning which has been exposed t o air and is well coated with oxide.
DEMONSTRATION
1. Attempt t o ignite 2 X 4 block with a match. Ignite shavings with a match. Gently blow or shake sawdust into the flame (hold the burner horizontally t o prevent solids from falling into burner tube). 2. Hold magnesium block or bar in the flame. Ignite magnesium ribbon in the flame (use tongs). Sift magnesium powder into the flame (a salt shaker makes a good dispenser).
REMARKS
Assuming a constant air (oxygen) supply, consider the effects of the following: flame t,emperature, rate of production of heat by the flame, heat capacity of the object placed in the flame, heat conductivity of the object placed in the flame, temperature obtainable in the heated object, area and nature of surface of the object heated. Jouinal o/ Chemical Education
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Decembr 1961
