14 SCIENCE OF HOME AND COMMUNITY 



B. Properties of oxygen, i. Invert one of the bottles and 

 put in it a burning splint. How does the action compare with 

 that in the air? Pour in a little limewater, shake the bottle. 

 The white precipitate shows the presence of carbon dioxid. 



2. Fasten a wire to a candle, light the candle and plunge it 

 into a second bottle. Note results. 



3. Put some powdered sulfur in a deflagrating spoon. Ignite 

 it in a flame and then lower it in a third bottle. Note the 

 difference between burning in air and in oxygen. 



4. Wrap a small piece of cloth around the end of an iron 

 picture wire. Roll this in powdered sulfur and hold it in the 

 flame. When it has started burning, lower it into a fourth 

 bottle of oxygen. 



5. What conclusions do you draw from these experiments 

 regarding the properties of oxygen and the difference between 

 burning in air and in pure oxygen? 



LABORATORY EXERCISE i 



Purpose. To study the burning of wood, soft coal, and hard 

 coal. 



Apparatus. Ringstand, wire gauze, gas burner or alcohol 

 lamp, small piece of wood, soft coal, and hard coal. 



Directions, i. Place a small piece of wood on a wire gauze 

 on a ringstand. Heat the wood. Place the gauze at such a 

 height above the flame that the wood is heated without bursting 

 into a flame. When the wood begins to smoke, hold a lighted 

 match above it. The flame formed is due to the burning of 

 the volatile substances driven off from wood by the heat. What 

 change takes place in the wood ? 



The substance left is charcoal. Apply a flame to it and see 

 if it will burn. How does the burning differ from that of the 

 volatile substances ? 



2. In a similar way try soft coal, using a piece about as large 

 as the end of your finger. 



3. Repeat the experiment, using hard coal. What difference 

 do you note in the burning of the two coals? The substance 

 left after the first heating is coke. Will this burn ? 



