EVAPORATION 105 



8. All rivers run to the sea and yet the sea is never quite full. Why? 



9. In tropical countries, drinking water is kept cool by being placed 

 in porous earthenware jars through the walls of which part of the water 

 escapes and evaporates. How does this keep the rest of the water cool? 



10. Which would register higher, a thermometer with its bulb covered 

 with a wet cloth or one with its bulb dry? Why? 



11. How would much moisture in the air affect the height of a wet- 

 bulb thermometer? 



12. Housekeepers find that water "boils away" faster on some days 

 than on others. How do you account for this? 



13. Put a crystal of iodine into a test-tube and heat gently over the 

 bunsen burner. What is the result (52)? 



14. Account for the fact that when a piece of camphor gum is exposed 

 to the air, its odor may soon be noticed at some distance from the 

 substance. 



16. Explain how wet cloths hung out on a cold day may "freeze dry;" 

 that is, may freeze and then dry. 



16. How does fanning cool us when we are warm? 



17. Why does a baked potato weigh less than it did when raw? 



18. Why do clothes dry most rapidly on a windy day? 



19. Why do strong winds rapidly dry the soil? 



20. When there is no perceptible movement of the air, one can often 

 discover which way it is moving by wetting the finger and holding it 

 up in the air. Explain. 



