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.
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