10th science Refresher Course 6 Answer English Medium HEAT

EVALUATION

I.  Choose the correct answer

1.  Calorie is the unit of a

a. heat               

b.  work              

c.  temperature             

 d. food

2.  SI unit of temperature is

a. Fahrenheit        

b. joule              

c. celsius          

d. kelvin

3.   In which mode of transfer of heat, molecules pass on heat energy to neighbouring mole- cules without actually moving from their positions?

a. Radiation        

b.  Conduction      

c. Convection          

d. Both b and c.

II. Fill in the blanks

1. The fastest mode of heat transfer is ________         

Answer :  radiation

2. During day time, air blows from  _________ to _________

Answer : sea , land

3. Liquids and gases are generally conductors of heat ____________

Answer : convection

4. The fi ed temperature at which matter changes state from solid to liquid is called ______       

Answer : latent heat

III. Answer briefly

1.  Define conduction.

• The  process  of  heat  transfer  in  solids  from  the  region  of  higher  temperature  to  the region  of  lower  temperature  without  the  actual  movement  of  atoms or molecules is called  conduction

2.  Ice is kept in a double-walled container. Why?

• Iceiskeptinadouble-walledcontainersoastopreventmeltingoficefromtheheatabsorbed presentintheimmediatesurroundings.Thevacuumpresentinbetweenthetwowallsprevents thetransferofheatfromthefirsttothesecondwallandhencetheiceremainsinthesolidform foralongertimeperiod.

3.  How does the water kept in an earthen pot remain cool?

Anearthenpotconsistsofsmallporesfromwhichthewaterinsidethepotconstantlyseepsout andgetsevaporatedduetothepresenceofhightemperaturearoundit.Theevaporation processrequiresheatwhichisacquiredfromthesurfaceofthepot,hencemakingthewater andthepotcooler.

4.   Differentiate convection and radiation.

5.  Why do people prefer wearing white clothes during summer?

6.  What is specific   eat capacity?

• Thespecificheatcapacityofasubstanceisdefinedastheamountofheatrequiredtoraisethe temperatureof1kgofthesubstanceby1°Cor1K.