156 ELEMENTARY GENERAL SCIENCE CHAP. 



(1) It remains liquid through a long range of temperature ( - 40 C. 

 to 357 C.). 



(2) It expands considerably for a small rise of temperature. 



(3) Its amount of expansion for one degree rise of temperature is 

 fairly uniform while it remains liquid. 



(4) It is a good conductor of heat, and therefore it quickly assumes 

 the temperature of objects surrounding or touching it. 



(5) Comparatively little heat is required to raise its temperature, 

 that is, it has a low specific heat. 



(6) It can be easily seen, and does not wet the glass contain- 

 ing it. 



Thermometric Scales. The distance between the marks of freezing 

 and boiling points on the stem of a thermometer may be divided as 

 follows : 



Fahrenheit scale. Centigrade scale. 



Boiling point 212 100 



Freezing point 32 



Discrimination between Heat and Temperature. 



Heat. Temperature. 



Dependent on the energy of Dependent on the velocity of 



the vibration of the particles of the vibration of the particles of a 



a body. body. 



Capable of producing change Is changed by the addition or 



x of temperature. withdrawal of heat. 



Measured in heat-units. Measured by degrees. 



Analogous to water flowing Analogous to difference of 



from high to lower levels. level. 



Capacity for Heat. Some substances have a greater capacity for 

 heat than others. This is analogous to vessels of different sectional 

 area. 



Capacity to hold Liquids. Capacity for Heat. 



The same quantity of water The same quantity of heat 



poured into a narrow and into produces different temperatures 

 a wide jar produces different (heat level) in equal masses of 

 changes of level. different substances. 



A wide jar contains a greater A body having a large heat 



quantity of water than a narro\v capacity, if at a given tempera- 

 one filled to the same height. ture, contains a greater quantity 



of heat than the same weight of 

 a substance of less capacity for 

 heat at the same temperature. 



Quantity of Heat. The amounts of heat absorbed (or given out) 

 by equal weights of different materials when heated (or cooled) 

 through the same range of temperature are in general different. 



The Capacity for Heat or the Specific Heat of a body is the number 

 of units of heat required to heat one gram of a substance through 



