OBSERVATIONS OF CHANGE OF TEMPERATURE 49 



Gold . . . -00004411 



Hydrogen sulphate . -000489 



Ice . . . . -0001585 



Iron . . . -0000355 



Lead . . . -000084 



Platinum . . . -000026 



Mercury . . . -00018 



Silver '. . . -0000583 



Tin . . . ~ . -000069 



Zinc . . . . -000089 



The coefficient of linear expansion, or the increase in unit 

 length, is approximately one-third the cubical coefficient. 



Additional Exercises and Questions. 



1. Show that we make use of the same reasons in determining that 

 two temperatures are alike as in determining that two quantities of 

 matter are alike. But show also that we cannot compare two tempera- 

 tures as we compare two quantities of matter. 



2. Compare the results given by a thermometer with your own sen- 

 sations when various objects, metallic and otherwise, are touched. 

 What explanation can be given of the apparent discrepancy ? Ascer- 

 tain the temperature of your own body before offering an explanation. 



3. Give the precise meaning to be attached to the terms ' heat ' and 

 ' temperature.' In what way may ' heat ' be looked upon as a quantity ? 



4. Classify the chief changes which may proceed simultaneously 

 with changes of temperature in a body. 



5. Observe the effect of raising the temperature of a tightly stretched 

 wire. Suggest other methods of showing expansion and contraction 

 with change of temperature. 



6. Find the length of a brass and of an iron rod, first when they 

 are placed in ice, and, secondly, after immersion in hot water of which 

 the temperature is taken. Calculate from your observations the frac- 

 tion of the length at zero by which each has increased during the 

 observed change of temperature, and also the average increase for a 

 change of 1. The decimal fraction obtained from the latter calculation 

 is called the coefficient of linear expansion. Measure by an eyepiece, 

 connected with a vernier, travelling along a graduated bar. 



7. Fit corks carrying glass tubes into flasks of equal capacity filled 

 with water, turpentine, and mercury, so that no air remains in the flask 

 and the liquids rise within the tubes to a convenient level. Rule lines 

 at a distance of half a centimetre on strips of paper and gum them to 



