AIR AND LIVING THINGS 



by changing the of its vibrating columns. 



9. A short string has a (lower, higher) pitch than a 



long string of the same material and diameter. A long air 

 column has a (lower, higher) pitch than a short column. 



10. A phonograph record when played fast appears to 

 have (higher, lower) pitch. 



11. Pitch depends upon the number of per second. 



12. Sound travels in air (1100, 2000) feet per second 



at thirty-two degrees Fahrenheit or zero degrees centigrade. 



13. Often an echo reflected from a building or hill blends 

 in with the sound of the vibrating object and may not fie 



distinguished from it. Infer the probable cause of this. 



14. On the basis of the facts learned in this topic, infer 

 why it would be impossible as far as scientific knowledge 

 now goes to receive sound signals from other planets in our 

 solar system such as Venus or Mars. 



15. When a violinist tunes his violin he turns small axles 

 to which the strings are attached. Infer how this changes 

 the pitch of the strings. 



16. Musicians in an orchestra always warm up their wind 

 instruments before playing. Can you infer a reason for this? 



TOPIC 5. AIR AND LIVING THINGS 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What are the differences between physical and 

 chemical changes? 



2. Of what is air composed? 



3. What is the nature of burning? 



4. Why do plants and animals breathe ? 



5. What is the importance of fresh air and how 

 is it best obtained in our buildings? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Follow the same method as outlined in Topics 1 

 and 2. 



2. Try to find answers to the following questions 

 either by reference study or by experiment. 



a. Problem 1 



What is a physical change? 

 What is a chemical change? 



How do substances appear after each has taken 

 place? 



b. Problem 2 



How may air be taken apart? (See Experiment 13.) 

 How may the parts be tested? (See Experiment 13.) 



c. Problem 3 



What happens when a can rusts? 



Will anything burn without air? (See Experiment 

 16.) 



How does the weight of a substance compare be- 

 fore and after burning? 



Is air the same before and after a substance has 

 been burned in it? 



d. Problem 4 



What do plants and animals take out of the air? 

 What do plants and animals give back to the air? 

 What use is made of the substance taken in? 

 What is oxidation? 



Compare in detail a burning candle with oxidation 

 in a plant or animal. 



e. Problem 5 



How does exhaled air compare in weight, volume 

 for volume, with fresh air? 



How should windows be regulated to care for 



this difference? 



What precautions are necessary in ventilating a 



room? 



3. You may find the following new words and 



phrases in this study : 



compound a new substance formed when two or more 

 simple substances combine chemically. 



element a simple substance which cannot be broken 

 down into simpler substances ; for example, sulphur, 

 tin, zinc, aluminum, hydrogen, nitrogen. 



exhale to breathe out. 



hemoglobin the substance which gives the color to 

 red corpuscles in the blood. 



inhale to breathe in. 



kindling temperature the temperature at which a sub- 

 stance takes fire and burns. 



mixture a combination of two or more substances in 

 such a way that their nature is unchanged ; for ex- 

 ample, a mixture of lead shot and sand. 



molecule the smallest particle of a substance which 

 still retains the properties of that substance ; for ex- 

 ample, the smallest particle of wood, leather, glass. 



oxidation chemically combining some substance with 

 oxygen as the burning of coal or the rusting of a 

 can. 



oxide a chemical compound made up of oxygen and 

 some other substance. 



respiration the exchange of gases between living 

 things and the air. 



ventilation providing a free circulation of fresh air in 

 a room or building. 



EXPERIMENTS OR DEMONSTRATIONS THAT WILL 

 HELP ANSWER THE PROBLEM QUESTIONS 



Experiment 13. How may air be separated into its 

 parts? 



Moisten the inside of a test tube. Pour in iron filings and 

 then pour out all that do not cling to the inside. Invert the 

 test tube in a dish of water and leave for 24 hours. Test the 

 gas remaining in the tube with a lighted splint. 



In your notebook 1 record the notes of this experiment and 

 complete the statements given below. 



The water in the tube about of the way toward 



1 See accompanying workbook, p. 9. 



