124 JUNIOR GRADE SCIENCE 



QUESTIONS ON CHAPTERS XIX. AND XX. 



90. If you were given water to which sand and nitre had been added, 

 describe how you would proceed, and make sketches of the apparatus yon 

 would employ, in order to prepare pure specimens of each. 



91. A careful observation of the effect of heat on some substances has 

 led to important evidence as to the nature of their composition. Give two 

 examples to illustrate this, recording the changes that may be observed, 

 and stating any conclusions you would draw from them. 



92. What is a crystal ? Describe exactly how you would proceed in 

 order to prepare large crystals of copper sulphate from an impure specimen 

 of the salt. 



93. Being given a liquid, what experiments would you perform to ascertain 

 whether it contains water, whether it is water, or whether it is a solution 

 of salt in water ? 



94. When substances burn they are said to have removed something 

 from the air ; how has this been proved ? Illustrate your answer by 

 reference to burning phosphorus or a burning candle. 



95. How would you show that air consists chiefly of two gases, and how 

 would you proceed to determine the proportion in which they occur ? 



96. When phosphorus is burned in a closed vessel it uses up only a portion 

 of the air. Why is this ? 



Mention the properties of the gas remaining. 



97. Describe what you have observed when (a) a candle, (6) a piece of 

 phosphorus, burns in an enclosed volume of air. Sketch the apparatus 

 used. What are the properties of the gas left in each case ? 



