42 NATURAL RESOURCES OF HOME ENVIRONMENT 



water remain in the funnel? If the mouth of the tube M is deep 

 in the water when the clamp is opened, and the water runs out of the 

 funnel, what evidence do you see to prove that something is leaving 

 the bottle? 



What air really is. Were any one of us to think over all 

 the possible uses of air, we would probably say its most im- 

 portant use is in the human body, for do we not all use air 

 in breathing? But is breathing anything like burning? 

 Experiments may help us to find this out. If we cover a 

 burning candle with a glass tumbler or cheese dish we 

 notice that the candle goes out in a short time. If we 

 uncover the candle and light it again it will go on burning. 

 If we cover it, it goes out again as before. It is evident that 

 some change takes place in the air during the burning of the 

 candle. Perhaps something in the air is necessary for the 

 burning and it is quickly decreased when we limit the 

 supply of air by inclosing a burning candle in the tumbler. 



We are told by men who have analyzed air that about 99 

 per cent of it is made up of the two gases, oxygen and nitro- 

 gen. If we prepare these gases and study their properties, it 

 may help us to explain the part that the air plays in burn- 

 ing matter and in supporting life and also to show us 

 whether it is the oxygen or the nitrogen which is used 

 in these processes. 



Experiment. To prepare and to observe the properties of the principal 



gases in the air. 

 i. OXYGEN 



Materials: Small wide-mouth bottle or glass. Glass cover. Wood 



taper. Oxone. Candle. 



Method: Drop a piece of oxone about half an inch square into the 

 glass tumbler containing a small amount of water. Light the wood 

 taper. Blow out the flame, leaving a glowing coal at the end. 

 Thrust this into the glass. Name the characteristic property of 

 oxygen shown Will the candle burn in oxygen? 



