264 Domestic Science 



5. Make a list of all the properties of oxygen, both physical' 

 and chemical, with which you are acquainted. 



6. Devise a method of finding out if the solution of oxygen 

 itself in water is acid or alkaline. 



7. By what tests would you show the nature of the products 

 formed in Experiment 113 ? 



8. Classify as far as you can all the chemical reactions already 

 mentioned in the text as (a) cases of synthesis or analysis ; (6) exo- 

 thermic or endothermic. Try to draw a conclusion from the com- 

 parison of the groups into which the reactions fall when arranged 

 under these four heads. 



9. Oxygen supports combustion much more vigorously than 

 air. What reason can you suggest for this ? 



10. Before Lavoisier's day substances, such as zinc, when burnt, 

 were supposed to give up a peculiar substance, termed "phlogiston", 

 which was restored to them when they were caused to resume the 

 metallic state by any suitable means. Suggest an experiment by 

 which the accuracy of the former part of this statement may be 

 tested. 



CHAPTER XVI 



PHYSICAL PROPERTIES OF WATER 



182. A certain amount of information concerning 

 the nature of water may be obtained from our previous 

 work on that substance. We already know that it is 

 a colourless liquid, with a density of 1 g. per c.c., freez- 

 ing at C., and boiling at 100 C. under an atmospheric 

 pressure of 760 .mm. We have, further, made use of its 

 power as a solvent for salt and similar bodies. In the 

 state in which it naturally occurs, water is never quite 

 pure, and the water which we ordinarily make use of 

 for washing and drinking purposes contains small 

 quantities of other substances dissolved in it. With 



