Carbon Dioxide (page 2)

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Author: Janice VanCleave

Design Your Own Experiment

  1. Organic fuels, which are compounds containing carbon (wax, for example), produce carbon dioxide when burned. Demonstrate this by burning a candle and collecting and testing the gas produced. Place about 1 inch (2.5 cm) of limewater in the bottom of a 1-quart (1-liter) jar. Wrap the end of a 12-inch (30-cm) wire around the center of a 2-inch (5-cm) long candle. Twist the wire to make along handle (see Figure 33.2 on the following page). Light the candle and hold the end of the wire to lower the candle into the jar. Cover part of the mouth of the jar with its lid. Allow the candle to burn until the flame goes out. Immediately remove the candle. Secure the lid on the jar and shake the jar vigorously four or five times. A milky solution indicates the presence of carbon dioxide. Display diagrams of a burning candle and of a car, indicating carbon dioxide molecules being emitted from the exhaust of the car and above the flame of the candle.
  2. One of carbon dioxide's chemical properties is that it combines with limewater to produce insoluble calcium carbonate. Another important chemical property is that it does not burn or support combustion. Because of this property, carbon dioxide is used in fire extinguishers. Demonstrate this by wrapping a 12-inch (30-cm) wire around a 1-inch (2.5-cm) long candle. Light the candle and hold the end of the wire to lower the candle into a 1-quart (1-liter) jar. In a small-mouthed gallon jug mix together 1 teaspoon (5 ml) of baking soda, 14 cup (63 ml) water, and 14 cup (63 ml) of vinegar. When the fizzing stops, hold the mouth of the gallon jug over the mouth of the jar and slowly tilt the jug. Do not allow any liquid from the jug to enter the jar. The invisible, heavier-than-air carbon dioxide gas flows into the jar and extinguishes the flame. Display photographs showing the sequence of events in this reaction along with pictures of carbon dioxide fire extinguishers.
  3. Its Production and Uses

  4. Respiration is the chemical process by which animals convert food into energy. Carbon dioxide is a by-product of this reaction and is expelled by the lungs. Test for this gas in your breath by exhaling through a straw into a soda bottle half filled with brom thymol blue solution (see Appendix 6). Brom thymol blue is an indicator that turns yellow in the presence of an acid. Carbon dioxide plus the water in the indicator produces carbonic acid resulting in a green to yellow color depending on the amount of carbon dioxide present.

Get the Facts

  1. The temperature of the earth is kept warm due to gases, such as carbon dioxide, in the atmosphere. The atmospheric gases trap warmth from the sun, just as glass traps warmth in a greenhouse. For this reason, this warming of the earth is called the greenhouse effect. Scientists think the earth's atmosphere is getting warmer because of the increase of carbon dioxide production. Find out more about the greenhouse effect. The burning of fossil fuels is considered the major cause of the increase of carbon dioxide, but other factors contribute to the increase of this gas. What are they? If the earth's atmosphere is getting warmer, how much warmer is it? What effect does this extra heat have on the earth's environment? Can the warming be stopped?
  2. Limestone caverns and the stalagmites and stalactites in these structures are formed from the combination of carbon dioxide and limewater in the soil. Find out more about the chemical reactions involved in the formation of limestone.
  3. Find out more about the uses of carbon dioxide such as the following:
    • carbonated drinks
    • leavening agent in baking
    • photosynthesis reaction
    • stimulus for the nerve controlling the diaphragm
    • agent in baking soda and washing soda made by the Solvay process
    • solid carbon dioxide, dry ice, a refrigerant
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