THERMAL PROPERTIES OF MATTER.pptx

8/9/2019 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:

.

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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THERMAL PROPERTIES OF MATTER.pptx