General Thought Questions 613 



22. Does matured seed suffer from exposure to freezing temperature? 

 Explain. 



23. Why are many dead young trees found in any dense natural forest? 



24. Name several ways in which we would be seriously affected by a 

 shortage of lumber supplies. Name several instances of the substi- 

 tution of other materials for wood in the making of articles we use. 



25. Name the plants that had a part in providing your last night's dinner. 



26. What harm do weeds do in the vegetable garden? 



27. Name several plants that had a part in furnishing your home. 



28. (a) How would you prove that bacteria are found in food and water? 



(b) Mention three ways in which bacteria are useful to us and two 

 ways in which they are harmful to us. 



(c) State one thing that Jenner, Lister or Pasteur did to aid us in the 

 control of bacteria. 



29. Are all foods preserved in the same way? Explain. 



30. (a) Describe (indicating four steps) an experiment to prove that a 



solid or a liquid occupies more space when heated than when cold, 

 (b) Make two labeled drawings to illustrate your description. 



31. To which special science should we look for a full understanding 

 of the principles governing: plant growth; the movements of the 

 planets ; the working of an electric washing machine ; the changes 

 that occur in cooking food; the circulation of the blood? 



32. What advantages has a dirigible over an ordinary balloon? 



33. (a) Describe fully how you would set up and use apparatus to show 



how soil water gets into the roots of plants. 



(b) To make your description clear, use at least two fully labeled 

 drawings showing different stages of the process. 



(c) What must soil water contain in order to be of the greatest use 

 to plants? 



34. (a) Name two substances required that burning may occur, whether 



rapidly in a burning candle or more slowly in a living human 

 being. Explain why each substance is necessary. 



(b) What two substances are given off by both a burning candle and 

 a living human body? 



(c) Of what process going on in the candle and in the human body 

 are these substances a result? Explain fully. 



(d) How may it be proved that one of these substances is given off 

 by the candle and by the human body? 



35. Name several plants used as foods by both man and animals. 



36. Leave a blanket out on the lawn for two or three days and the grass 

 under it begins to turn yellow. Why? 



37. Describe one recent invention which has had an effect on your life. 



38. Which general topic in this book has interested you most? Why? 



