Q. Why does heat flow from hot body to cold body?
Ans.
Due to temperature difference heat
flows from hot body to cold body. The molecules of hot body have greater kinetic
energy than the molecules of cold body. The molecules of hot body give their
energy to the molecules of cold body. In this way heat flows from hot to cold
body.
Q. Define the terms heat and temperature.
Ans.
Heat:
“Heat is the energy that is transferred from
one body to the other in thermal content with each other as a result of the
difference of temperature between them”
Temperature:
The degree of hotness or coldness of the body is
called “temperature”.
Q. What is meant by internal energy of a body?
Ans.
Internal
energy:
“The sum of kinetic energy and potential
energy associated with the atoms, molecules and particles of a body is called
its “internal energy”.
Q. How does heating affect the motion of molecules of a
gas?
Ans.
On heating a gas, the kinetic energy and temperature of the gas increases. Hence
the internal energy of the gas increases.
Q. What is a thermometer? Why mercury is preferred as a
thermometric substance?
Ans.
A device used to measure the temperature is called “thermometer”. Mercury
is preferred as thermometric substance due to the following reasons:
Low freezing point very
high boiling point
Less
specific heat low
heat capacity etc.
Q. Explain the volumetric thermal expansion.
Ans.
The change of volume on heating is called “volumetric thermal expansion”.
Q. Define specific heat. How would you find the
specific heat of a solid?
Ans.
The heat required to raise the temperature of unit mass of substance through
one Kelvin is called “specific heat”. To find the specific heat of
a solid method of mixture is used.
Q. Define latent heat of fusion.
Ans.
Latent
heat of fusion:
“Heat
energy required to change unit mass of a substance from solid to liquid state
at its melting point without change in its temperature is called its latent
heat of fusion”
Q. Define latent heat of vaporization.
Ans.
Latent
heat of vaporization:
“The
quantity of heat that changes unit mass of a liquid completely into gas at its
boiling point without change in its temperature is called its latent heat of
vaporization”
Q. What is meant by evaporation? On what factors the
evaporation of a liquid depends? How cooling is produced by evaporation?
Ans.
The conversion of liquid into vapours without heating
is called “evaporation”. it takes place at
any temperature of liquid.
Evaporation
depends upon the following factors:
o
Temperature
o
Surface
area
o
Wind
o
Nature
of liquid
When fast moving molecules of liquid escape out from
the surface of liquid due to evaporation the kinetic energy and temperature of
the remaining liquid decreases. Hence cooling is produces due to evaporation.
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