# Slow Burn

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#### Updated on Feb 08, 2012

Grade Level: 6th - 8th; Type: Chemistry

### Objective:

To investigate how temperature of a room affects the burn rate of a candle.

### Research Questions

• What causes a candle to burn?
• Does temperature affect the way a candle burns?

Candles were used to provide light in the darkness long before electricity was discovered. Today candles are still used for enjoyment and in emergency situations. Candles are made of different types of wax including paraffin, soy, bee, plant, or animal fat. The wax in a candle provides the fuel to keep the candle burning. When the wick, an absorbent piece of string is lit, the heat from the fire melts the wax. The liquid wax moves up the wick releasing a vapor that burns. The wax vapor also coats the wick, keeping it from burning.

### Materials:

• 6 taper candles (candles must be the same in size, color, and manufacturer)
• 6 candle holders
• paperclip
• ruler
• matches or lighter
• timer
• thermometer
• small closed room with air-conditioning
• space heater
• paper
• pencil

### Experimental Procedure

1. Gather the necessary materials.
2. Turn on the air-conditioner in a small room that can be closed up. Place the thermometer in the room. Allow the room to cool to a temperature of about 60 to 65 degrees Fahrenheit.
3. Using a paperclip, scratch a label at the bottom of each candle – C1, C2, C3 for the cold room candles and W1, W2, W3 for the warm room candles. Measure the length of the candles and record.
4. Set three candles upright in the room and have an adult light each candle. Allow the candles to burn for 30 minutes. At the end of 30 minutes, blow the candles out and measure each of the candles’ lengths and record.
5. Subtract the difference between the original candle length and its length after burning for 30 minutes. Record the difference. Find the average length burned by adding the burned lengths of the three candles and dividing by three.
6. Turn the air-conditioner off in the room. Turn the heater on and turn on the space heater. Heat the room to a temperature of about 80 degrees Fahrenheit.
7. Set the remaining three candles upright in the room and have an adult light each candle. Allow the candles to burn for 30 minutes. At the end of 30 minutes, blow the candles out and measure each of the candles’ lengths and record.
8. Again, subtract the difference between the original candle length and its length after burning in a warm room for 30 minutes. Record the differences. Find the average length burned by adding the burned lengths of the three candles and dividing by three.
9. Analyze the results and draw a conclusion.

Terms/Concepts: wick: a band of woven fibers like a string that supplies fuel to a candle by capillary action capillary: a fine hole or passage paraffin: a flammable, waxy substance used to make candles; Light from the candle comes from a chemical reaction caused by setting fire to the wick. The heat travels from the wick to the wax. The wax turns into a hot liquid that then travels up the wick. The candle continues to draw hot vapors from the wick allowing it to continue to burn.

References:

“How Does a Candle Work?” http://home.howstuffworks.com/question267.htm “Candles” at http://www.explainthatstuff.com/candles.html “The Science of Candles” at http://www.candles.org/candlescience.html

Nancy Rogers Bosse has been involved in education for over forty years - first as a student, then as a teacher, and currently as a curriculum developer. For the last fifteen years she has combined a career in freelance curriculum development with parenthood - another important facet of education and probably the most challenging. Nancy lives in Henderson, Nevada with husband and their three teenagers.