126 



RELATION OF HEAT TO COMFORT 



TOPIC 2. HOW HEAT AND TEMPERATURE ARE MEASURED 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What is heat? 



2. How is temperature measured? 



3. How are thermometers constructed? 



4. How do we measure heat? 



5. Do substances vary in their ability to absorb 

 heat? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Read carefully the problems listed above, and 

 see if you understand them before you begin to work. 



2. Heat and temperature are not the same. Make 

 certain that you know the correct meaning of each 

 term. 



3. In connection with problems 2 and 3, secure a 

 centigrade and a Fahrenheit thermometer from your 

 instructor. Place them side by side and make diagrams 

 showing a comparison of the two scales. See Experi- 

 ment 88. 



4. You will find the following words in the study 

 of this topic. If they are new to you, study them care- 

 fully and use them as often as possible in order that 

 they may become a part of your vocabulary. 



expand to become larger. 



contract to become smaller. 



Calorie amount of heat required to raise one kilogram 

 of water one degree centigrade. This is known as 

 the "great" or kilogram Calorie. It is always spelled 

 with a capital C. 



calorie the amount of heat required to raise the tem- 

 perature of one gram of water one degree centi- 

 grade. This is known as the gram calorie and is 

 always spelled with a small c. 



kilogram 1000 grams. 



ounce about 28.4 grams. 



EXPERIMENTS OR DEMONSTRATIONS WHICH WILL 

 HELP ANSWER THE PROBLEM QUESTIONS 1 



Experiment 86. Is heat a substance having weight? 



Secure a metal ball and weigh it on a good balance. Heat 

 a jar of water to boiling and measure the temperature of 

 the water with a thermometer. Heat the ball by immersing 

 it in the hot water. Weigh the ball again on the balance. 

 Did the metal ball gain in weight when it was heated? Is 

 heat a substance? Find a definition of heat. 



Experiment 87. Can we tell temperature accurately by 

 touch? 



Heat water in a large vessel until it is comfortably warm. 

 Divide the water in two pans. Hold one hand in very cold 



1 See workbook, p. 44. 



water and the other in warm water for several minutes. 

 Quickly put one hand in each pan of water. Does the water 

 feel at the same temperature to both hands? Is your sense 

 of temperature reliable? Why do doctors use a thermometer 

 in determining the temperature of a patient instead of 

 touching the patient's head or arms? 



Experiment 88. How is a thermometer constructed? 



Obtain a Fahrenheit and a centigrade thermometer to 

 compare them. How are they made? What liquid is used 

 in the bulb. How do you hold the thermometer when read- 

 ing it? What is the boiling point of water on each ther- 

 mometer? What is the freezing point of water? Put the 

 bulbs of the thermometers in cold water and take tempera- 

 ture readings. Then put the bulbs of the thermometers in 

 hot water. Take the readings again. Why do the columns of 

 liquid move? Make drawings of the scales. 



READINGS WHICH WILL HELP ANSWER 

 THE PROBLEM QUESTIONS 



What is heat? Man was puzzled for many centuries 

 as to whether heat is matter or energy. Until about a 

 century ago heat was thought of as a substance and 

 was spoken of as such under the name of "caloric." 

 Heat was considered as matter just as we think today 

 of air, water, and metals as matter or substances. 



A simple experiment is suggested at the begin- 

 ning of this topic through which you can determine 

 whether heat is matter or a form of energy. If a cool 



FIG. 196. DIFFERENCE BETWEEN HEAT 

 AND TEMPERATURE 



metal ball is weighed, then heated and weighed again, 

 its weight remains the same. If heat were a sub- 

 stance, since all substances have weight, the ball 

 should gain weight as it becomes hotter. Since the 

 ball did not gain in weight after it was heated, we 

 conclude that heat is not matter. It is true that the 

 metal ball increased in size, for nearly all substances 

 expand when they are heated, but its weight remained 

 the same. 



Heat, therefore, is a form of energy. Scientists now 

 believe that heat is a rapid motion of molecules. The 

 hotter a substance is, the faster its molecules are 



