32 EXPERIMENTAL GENERAL SCIENCE 



arm's length. The chemical reaction will produce zinc sulphide. Is this 

 an element or a compound? Why? 



6. Of what use was heat in the foregoing experiment? 



7. Can you write the formula for zinc sulphide? 



8. Place a small quantity of mercuric oxide (HgO) in a test-tube, 

 and heat strongly. What change in the color of the substance do you 

 notice? 



9. What is left in the cooler part of the test tube after it is heated? 



10. What becomes of the other element? 



11. What did the application of heat do in this experiment? 



12. How did this experiment differ from that in question 5? 



13. When a ton of wood is burned more than a ton of gas goes up the 

 chimney. How do you explain this? 



14. Why is it necessary to know the temperature of the solutions when 

 developing films, prints, and negatives in photography? 



16. Of what use is heat in cooking food other than softening the 

 food and killing the germs? 



