Do you know if phosphorus, potassium and calcium exist in 

 nature in their pure state ? 



Does oxygen exist anywhere in a pure or uncombined state ? 



Of what is water composed ? Write its chemical formula. 



Of what is ammonia composed ? Is it a gas or liquid ? Can 

 you buy pure ammonia at the drug store ? 



Does the plant feed on ammonia directly ? 



What is the composition of a nitrate? Write the formula for 

 nitrate of potash and nitrate of lime. 



In what kind of materials does nitrogen occur? Name some 

 common things which you think contain nitrogen. 



Is nitrogen a solid or a gas? 



