thermal properties of matter.pptx
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kendriya vidyalaya no 2
delhi cantt chapter 11
thermal properties ofmatter
name :- Himanshu Tripathi
CLASS :- XI C
ROLL NO :- 52
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ontents:- Temperature
Measurement of temperature and temperaturesa!es
Idea "as e#uation Heat apait$
Spei% heat apait$ Ca!orimetr$ Chan"e of state Latent heat Heat transfer Condution Con&etion Radiation Ne'ton(s %rst !a' of oo!in"
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mperature:-
The atoms and molecules in
a gas are in constant motion.
Temperature is a measure of
the speed with which theymove. (More exactly it is a
measure of their average
kinetic energy.) The higher
the temperature, the faster
the molecules move.
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ea! )as *#uation:-"' n&T (Macroscopic orm)
*asically says that the state of a gas is also dependent on the
num!er of particles in the sample of gas. +o, !y adding a term
for the num!er of moles of particles and proportionality
constant &- to the com!ined gas law, we get #deal $as aw. n- is the num!er of moles of the gas.
&- the /niversal $as 0onstant is the same for all gases.
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The heat capacity 0 of an o!1ect is the heat energy needed
to raise its temperature !y 2 kelvin (or 2 degree celsius).3hen different su!stances undergo the same temperaturechange they can store or release different amounts of heat.+omething with high heat capacity heats up slower and
cools down faster.
eat Capait$:-
4eat 0apacity 5 6 T
Q7 thermal energy (8)
T7 temperature change (9)
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ei% Heat Capait$efined as the amount of thermal energy re;uired to produce
unit temperature rise in unit mass of the material./nit mass isnormally 2kg, and unit temperature rise is normally 29
+pecific 4eat 0apacity 5 6 (mT)
/nit:8 kg292,where m is the mass of the material
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0alorimetry means measurement of heat.3hen a !ody at
higher temperature is !rought in contact with another !ody atlower temperature, the heat lost !y the hot !ody is e;ual to the
heat gained !y the colder !ody, provided no heat is allowed to
escape to the surroundings. < device in which heat
measurement can !e made is called a calorimeter.
!orimeter$:-
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an"e of state:-The change of state from solid to li;uid is called melting and
from li;uid to solid is called fusion.The temperature at whichthe solid and the li;uid states of the su!stance in thermal
e;uili!rium with each other is called its melting point.
The melting point of a su!stance at standard atomspheric
pressure is called its normal melting point.
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Some important terms
The change of state from li;uid to vapour (or gas) is called
vaporisation.
The temperature at which the li;uid and the vapour states of
the su!stance coexist is called its boiling point.
The !oiling point of a su!stance at standard atmospheric
pressure is called its normal boiling point.
The change from solid state to vapour state without passing
through the li;uid state is called sublimation, and the
su!stance is said to su!lime.
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tent Heat:-The amount of heat per unit mass transferred during change of
state of the su!stance is called latent heat of the su!stance forthe process.
Q = m L
Where,
Q is the heat required, m is the mass of the substance
L is known as latent heat
#ts +# unit is 8 kg72.
The latent heat for a solidli;uid state change is called the
latent heat of fusion (Lf), and that for a li;uidgas state
change is called the latent heat of vaporisation (Lv).
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Re!ation-Condution+
Con&etion andRadiation:-
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ondution:-0onduction is the mechanism of transfer of heat !etween two
ad1acent parts of a !ody !ecause of their temperaturedifference. $ases are poor thermal conductors while li;uids
have conductivities intermediate !etween solids and gases.
4eat conduction may !e descri!ed ;uantitatively as the time
rate of heat flow in a material for a given temperaturedifference.
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ti
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0onvection is a mode of heat transfer !y actual
motion of matter. #t is possi!le only in fluids. 0onvection can!e natural or forced. #n natural convection, gravity plays an
important part. 0onvection involves !ulk transportof different
parts of the fluid. #n forced convection, material is forced to
move !y a pump or !y some other physical means.
n&etion:-
onvection cycle
di i
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0onduction and convection re;uire some Material as a
transport medium. These modes Of heat transfer cannotoperate !etween !odies +eparated !y a distance in vacuum.
*ut the %arth does receive heat from the sun across a 4uge
distance and we ;uickly feel the warmth Of the fire near!y
even though air conducts "oorly and !efore convection can setin. The Third mechanism for heat transfer needs no
Medium= it is called radiation and the energy +o radiated !y
electromagnetic waves is called &adiant energy.
adiation:-
The electromagnetic radiation emitted !y a !ody !y virtue of
its temperature like the radiation !y a red hot iron or light from
a filament lamp is called thermal radiation.
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ton(s ,st!a' of oo!in>ewton?s aw of 0ooling says that the rate of cooling of a
!ody is proportional to the
excess temperature of the !ody over the surroundings:
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T(t) = TA+ (TH-TA) e-kt
where T(t) = Temperatre at time t TA = Am!ient temperatre (temp of
srrondin"s)
TH = Temperatre of hot o!#ect at time $ k = positive constant t = time
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THE
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