22 



THE OCEAN OF AIR 



the top. The iron appeared to 



have changed color to a 



This substance is commonly 



called iron The gas left 



in the tube to support burn- 

 ing. If the brown iron rust is 

 made of iron and oxygen it has 



secured the from the air. 



If it has removed all of this 



substance about of the air 



is oxygen and about is 



other gases. 



FIG. 39 



Experiment 14. How may 

 oxygen be prepared? 



Set up the apparatus as shown 



in Figure 40. Place in the test tube a mixture of about 

 four parts potassium chlorate to one of manganese dioxide. 

 Replace the stopper. Heat the tube. Collect three bottles 

 of the gas in bottles which have been filled with water and 

 inverted in the pan. The bottles may be inverted by placing 

 a glass plate over the mouth of the bottle. Place a smouldering 

 splint in one bottle of the gas. Heat some fine iron wire in a 



FIG. 40 



flame and dip it into some sulphur. Light the sulphur and 

 plunge it into another bottle of the gas. Burn some other 

 substance in the other bottle of oxygen. 



In your notebook 1 record the notes of this experiment and 

 complete the statements given below. 



Things burn in oxygen than in air. Oxygen may be 



prepared by a mixture of '. and . Oxygen has 



no odor, , or 



Experiment 15. How may carbon dioxide be prepared? 



Insert a one-hole rubber stopper into the mouth of a 

 pint milk bottle. Through the hole in the stopper place a 

 six-inch length of glass tubing bent at an angle. Attach a 

 delivery tube to the generator. Place several lumps of marble 

 in the generator, cover them with water, and add some con- 

 centrated hydrochloric acid. Collect the gas by placing the 

 delivery tube in a bottle. Allow some of the gas to bubble 

 through the clear limewater as shown in Figure 41. This is 

 a test for the presence of carbon dioxide. Plunge a burning 

 splint into a bottle of carbon dioxide. Observe the results in 

 the generator and the tests. 



1 See accompanying; workbook, p. 9. 



In your notebook 2 record the notes of this experiment 

 and complete the statements given below. 



When the acid was 



poured on the a gas 



was given off which was heav- 

 ier than air as shown by the 

 way When the gas bub- 

 bled through limewater, the 



limewater changed to a 



color. A burning splint placed 

 in a bottle of carbon dioxide 



, showing that carbon 



dioxide will not burning. 



Experiment 16. What is 

 given out by a burning 

 substance? 



FIG. 



FIG. 42 



a. Wind a one-foot length of wire 

 several times around a piece of candle. 

 Light the candle and lower it into a 

 quart milk bottle or jar. Carefully ob- 

 serve what happens. Pour some clear 

 limewater into the jar, close the mouth 

 with your hand or a cork, and shake 

 thoroughly. 



b. Bring the burning candle near a 

 cool blackboard so that the flame 

 touches the slate, and observe what hap- 

 pens. 



In your notebook 3 record the notes 

 of this experiment and complete the 

 statements given below. 



When clear limewater was placed in the jar in which 



the candle had burned, it turned , showing that 



was given off as a product of the burning. The came 



from the while the came from the air. 



When the candle came in contact with the cold black- 

 board a little spot of was formed, showing that an- 

 other product of burning is 



Experiment 17. Does slow burning take place in the 

 body? 



Have several members of the class blow their breath 

 through the clear limewater and observe what happens. 



In your notebook 4 record the notes of this experiment and 

 complete the statements given below. 



When the breath was blown through clear limewater it 



, showing the presence of This is evidence that 



a which results in the formation of has taken 



place in the The came from the _ _ we eat while 



the oxygen came from the 



which we . 



Experiment 18. What are the important things in se- 

 curing good ventilation? 



Make an airtight ventilation box as illustrated in the 

 diagram (Fig. 43). A box about 12 x 12 x 10 inches is of a 

 good size. The front should be made with a sliding glass 

 door. Bore four holes in each end, two at the top and two 



! See accompanying workbook, p. 10. 

 * See accompanying workbook, p. 10. 

 'See accompanying workbook, p. 11. 



