80 FIRST YEAR COURSE IN GENERAL SCIENCE 



The use of steam for this kind of work about the year 1770 

 was the beginning of great progress in rapid travel on land 

 and sea and in the manufacture of cloth, tools, and food. 

 Electric power has recently displaced' steam in many kinds 

 of work; but unless natural water power is available, steam 

 is still relied upon to turn the machinery that is necessary to 

 make electric currents. 



EXERCISES 



1. Describe changes in the physical state of matter produced by 

 changes in temperature. 



2. Why does the mercury rise in the tube of a thermometer when 

 you put your finger on the bulb? How could you make it fall con- 

 siderably in a short time? 



3. How many Fahrenheit degrees are there between the freezing 

 and boiling points of water? How many Centigrade degrees? 



4. Which shows a greater change of temperature, one Fahrenheit 

 degree or one Centigrade degree? State the arithmetical relation be- 

 tween the value of a Centigrade degree and a Fahrenheit degree. 



5. How many degrees above F. is 9 P above freezing? How 

 many degrees above C. is 5 above freezing? Which is the higher 

 temperature? Why? 



6. Show why 32 is added in one case and subtracted in the second 

 case, in changing the readings of one thermometer scale to the other. 

 (See 75.) 



7. 68 F. is a comfortable house temperature. What is the equiva- 

 lent in degrees Centigrade? 



8. Which is the greater rise in temperature, from 32 F. to 50 F. 

 or from C. to 12 C.? Prove your answer. 



9. (a) Which has the higher temperature, 1,000 g. of water at 

 40 C. or 500 g. at 82 C.? 



(6) Which has the greater amount of heat, 1000 g. of mercury 

 or 500 g. of water at the same temperature. Explain. Give the 

 answer in calories. 



10. Why is there greater probability of a frost on a clear night than 

 on a cloudy night? 



