EXPERIMENT 2. — Put a lamp chimney over a lighted candle. Admit air from the bottom. Does the candle burn freely? Hold a strip of tissue paper near the bottom of the chimney, and also above the chimney. Explain the cause of movement of the paper. Cover the chimney on top and also exclude air from the bottom. Does the candle continue to burn ? Give reason. 7 8 DOMESTIC SCIENCE EXPERIMENT 3. — (To be performed by the instructor.) Float a cork with a small piece of phosphorus on it in a pan of water. Ignite the phosphorus and cover it quickly with a bell jar. (A fruit jar may be used.) With what does the phosphorus unite in burning to form the dense white fume ? What becomes of this fume as it disappears ? What part of the jar is filled with water? What component of the air has been burned out ? What com- ponent of the air remains in the jar, preventing the water from filling the entire jar? What proportion of the air is oxygen ? nitrogen ? EXPERIMENT 4. — To examine air for dust, bacteria, etc. Put a drop of glycerine on a clean glass microscope slide. Ex- pose to the dust of the room until the next lesson. Cover the glycerine with a cover glass and examine under a microscope, first with a low power and then with a high power. Make a drawing of what you see. Oxidation and Combustion. — Oxidation, or combustion, is the union of oxygen with any other substance. The process may be slow or rapid, but in either case heat is given off, even though not rapidly enough to be perceptible. Example : the rusting of iron is really the burning of iron, but the process is so slow that we do not detect the heat given off. Fuels are composed largely of carbon and hydrogen which, in burning, unite with oxygen of the air giving off heat. Products of Combustion. EXPERIMENT 5. — Hold a saucer in a candle flame. Note the black deposit that forms on it. What element is present in the candle? What is smoke? Do we get the maximum heat from fuel when smoke is given off during combustion ? Identification Test for Carbon Dioxide. — Put some filtered lime- water in a glass beaker or tumbler. Breathe through a glass tube AIR AND COMBUSTION 9 into the limewater, which will become cloudy from the carbon dioxide present in the breath exhaled from the lungs. This test is used to identify carbon dioxide, which always causes limewater to become cloudy. An excess of C02 causes the cloudiness to disappear. EXPERIMENT 6. — Hold a bell jar over a burning candle for a short time, collecting any gases which may be given off during com- bustion. Invert the bell jar, pour into it some filtered limewater, cover the jar, and shake well. Does the limewater become cloudy ? What gas was given off during the burning of the candle ? EXPERIMENT 7. — Cover a burning candle with a dry bell jar. Note the formation of water on the sides of the jar. Is the water a product of combustion ? Write the equation for the forming of H20. Summary of products of combustion : C + 0 = CO, carbon monoxide, a poisonous gas given off in com- bustion when the supply of oxygen is deficient. The blue flame on the surface of a coal fire is burning CO. All stoves should have perfect chimney connections to carry off this poisonous gas. C + 02 = C02, carbon dioxide. H2 + 0 = H20, water. Unconsumed carbon = smoke. Mineral matter = ash.

AI-modernized reading of the original text

EXPERIMENT 2. — Put a lamp chimney over a lighted candle. Admit air from the bottom. Does the candle burn freely? Hold a strip of tissue paper near the bottom of the chimney, and also above the chimney. Explain the cause of movement of the paper. Cover the chimney on top and also exclude air from the bottom. Does the candle continue to burn ? Give reason. EXPERIMENT 3. — (To be performed by the instructor.) Float a cork with a small piece of phosphorus on it in a pan of water. Ignite the phosphorus and cover it quickly with a bell jar. (A fruit jar may be used.) With what does the phosphorus unite in burning to form the dense white fume ? What becomes of this fume as it disappears ? What part of the jar is filled with water? What component of the air has been burned out ? What component of the air remains in the jar, preventing the water from filling the entire jar? What proportion of the air is oxygen ? nitrogen ? EXPERIMENT 4. — To examine air for dust, bacteria, etc. Put a drop of glycerine on a clean glass microscope slide. Expose to the dust of the room until the next lesson. Cover the glycerine with a cover glass and examine under a microscope, first with a low power and then with a high power. Make a drawing of what you see. Oxidation and Combustion. — Oxidation, or combustion, is the union of oxygen with any other substance. The process may be slow or rapid, but in either case heat is given off, even though not rapidly enough to be perceptible. Example : the rusting of iron is really the burning of iron, but the process is so slow that we do not detect the heat given off. Fuels are composed largely of carbon and hydrogen which, in burning, unite with oxygen of the air giving off heat. Products of Combustion. EXPERIMENT 5. — Hold a saucer in a candle flame. Note the black deposit that forms on it. What element is present in the candle? What is smoke? Do we get the maximum heat from fuel when smoke is given off during combustion ? Identification Test for Carbon Dioxide. — Put some filtered limewater in a glass beaker or tumbler. Breathe through a glass tube into the limewater, which will become cloudy from the carbon dioxide present in the breath exhaled from the lungs. This test is used to identify carbon dioxide, which always causes limewater to become cloudy. An excess of C02 causes the cloudiness to disappear. EXPERIMENT 6. — Hold a bell jar over a burning candle for a short time, collecting any gases which may be given off during combustion. Invert the bell jar, pour into it some filtered limewater, cover the jar, and shake well. Does the limewater become cloudy ? What gas was given off during the burning of the candle ? EXPERIMENT 7. — Cover a burning candle with a dry bell jar. Note the formation of water on the sides of the jar. Is the water a product of combustion ? Write the equation for the forming of H20. Summary of products of combustion : C + O = CO, carbon monoxide, a poisonous gas given off in combustion when the supply of oxygen is deficient. The blue flame on the surface of a coal fire is burning CO. All stoves should have perfect chimney connections to carry off this poisonous gas. C + O₂ = CO₂, carbon dioxide. H₂ + O = H₂O, water. Unconsumed carbon = smoke. Mineral matter = ash.

A textbook of domestic science for high schools