30 INTRODUCTION TO GENERAL SCIENCE 



Experiment 12. Absorption of Heat. 



Apparatus: The same as in Experiment 11. 



a. Put equal amounts of water of the same temperature 

 into the two cans, and expose them to the sunlight, in a place 

 which is sheltered from wind. Leave for twenty minutes and 

 then test the temperature of each. Which is warmer ? Did 

 you expect this ? Nearly all of the " laws " of nature work 

 both ways. 



Experiment for places where there is snow: Place squares 

 of different-colored cloth, including white and black, on the 

 surface of the- snow, in the sunshine. Some will absorb more 

 heat than others, and will sink deeper into the snow. Measure 

 the different depths, and arrange the colors in a table, accord- 

 ing to the amount of heat which they have absorbed in a 

 given time. 



22. MEASUREMENT OF HEAT 



Section 16 treated of the measurement of temperature, but 

 was not concerned with the measurement of heat. We have 

 learned that heat is due to the motion of the molecules. Now 

 the temperature of a body indicates the average velocity of 

 the molecules, while the quantity of heat is due to the sum 

 total of all of the molecular motion. 



The unit of heat measurement is the calorie, and it is the 

 amount of heat which is necessary to raise the temperature 

 of one gram of water from 4 to 5 Centigrade. (One ounce is 

 equivalent to about twenty-eight grams.)* This is the unit 

 which is used in all scientific work, but there is another unit 

 which is used in engineering. This is called the British 

 Thermal Unit, and it is the amount of heat which is necessary 

 to raise one pound of water one degree Fahrenheit. 



* A nickel five-cent piece weighs five grams. 



