x HEAT 157 



Transmission of Heat. Heat travels from one body to another by 

 conduction, convection, or radiation. 



Conduction. Convection. Radiation. 



The particles pass Hot particles move Due to the vibra- 

 on the heat vibra- away from the source tions of a heated 

 tions from one to of heat, and cooler body being trans- 

 the other. This is ones take their place. mitted through the 

 how solids get hot. This is how liquids ether : -example, the 

 and gases chiefly get heat of the sun trans- 

 heated, mitted through space 

 to the earth. 



Change of State. Many solids change into liquids, and liquids 

 into gases, at definite temperatures. .During these changes of state 

 heat is absorbed without rise of temperature. The change of state 

 generally involves a change of volume. 



latent . 



Solids + heat of = Liquids, 

 liquefaction 



latent 



Liquids + heat of = Gases, 

 vaporisation 



QUESTIONS ON CHAPTER X. 



1. (a) Why is the tube of a thermometer made with a narrow bore, 



while the bulb is large ? 

 (6) Why is the top of a thermometer sealed up ? 



(c) Why is mercury the best liquid to use in a thermometer 

 under ordinary circumstances ? 



(d) Under what circumstances is alcohol used instead of 

 mercury ? 



2. Enumerate the effects which ensue when a solid body is con- 

 tinuously heated. How would you show these effects experiment- 

 ally? 



3. Describe experiments to prove the expansion by heat of (a) a 

 solid, (b) a liquid. 



4. How are the "fixed points" of a thermometer determined ? 



5. Draw some distinctions between heat and temperature. 



6. Describe an experiment to show that different substances at the 

 same temperature have different quantities of heat. 



7. State the meaning of "conduction" and "convection" as 

 applied to heat. 



&. How would you prove that when ice is melted heat is absorbed 

 without rise of temperature ? 



9. State precisely what is meant by the statement that the 

 specific heat of mercury is '033. 



