Chapter 10 : Thermal Properties of Matter Flashcards
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10.1
define internal energy
internal energy is an energy store that is made up of the total kimetic energy associated with the random motion of the particles and the total potential energy between the particles in the system
10.1
heat capacity
heat capacity [c] of an object is the change in the amount of its interal energy per unit change in its temperature
formula : C = Q (amount of energy transfered, J to or from the internal store of the object by heating / change in temperature(K or C)
10.1
specific heat capacity
specific heat capacity c of a material is the change in amount of its internal energy per unit mass of each unit change in its temperature
c = C/m(mass) = Q/m*change in temperature(K or C)
qns
what is the SI unit of specific heat capacity & heat capacity
heat capacity : joule/kelvin ( J/K ) or joule/degree celsius ( J/’C )
Specific heat capacity : joule/kilogram/kelvin ( J/(kg K)) or joule/kilogram/degree celsiusc (J/(kg ‘C)
10.1
formula of Q
Q = energy transferred by heating to an object
Q = C ( heat capacity) change in temperature**
or
**Q = mc (specific heat capacity)x change in temperature
10.2
processes that invlove a change in state
freezing
melting
boiling
condensation
qns
difference betwee boiling & evaporation
boiling:
needs a heat source
vaporisation takes place throughout the liquid
rate of vaporisation faster
happens only at the boiling point
liquid temp remains constant
evaporation:
does not need heat source
takes place only at the liquid surface
rate of vaporisation slower
happens at temp below boiling point
liquid temp tends to drop
10.2
what affects rate of evaporation
pressure : pressure higher = rate pf vaporisation lower ( at higher pressure, liquid molecules escape into the air slowly )
temperature : when temp higher, rate of vaporation higher. at higher temp, average kinetic energy of liquid molecules is higher ( more liquid particles escape into the air )
humidity of air : rate of vaporation lower as there is more water vapour in the air originally ( humidity is the measure of amt of water vapour in the air )
wind speed : wind removes the molecules that has just escaped into the air, thus air surrounding the liquid is drier = rate of evaporation higher
surface area of liquid : larger exposed surface area = higher rate of evaporation ( more molecules can escape from the surface of the liquid )
boiling point of the liquid : lower boiling point = evaporate more quickly, higher boiling point = evaporate faster ( under similar conditions ) because attractive firces between particles with lower boiling point is weaker, change state faster = evaporate faster
10.3
define laten heat, L
Latent heat, L is the energy released/absorbed to change the state of a substance, at a constant temperature
SI unit : joules (J)
qns
what are the 2 types of latent heat?
latent heat of fusion [ for melting & solidifiation ]
latent heat of vaporisation [ for boiling & condensation ]
10.3
define latent heat of fusion
amount of energy transferred to change a substance between the solid and liquid states, at a constant temperature
Increase in the potential energy of particles but kinetic energy remains unchanged
10.3
specific latent heat of fusion
amt of energy transferred per unit mass of a substance to change between solid and liquid states, at constant temp
Lf ( latent heat of fusion J ) = lf ( specific latent heat of fusion J/kg ) * m( mass of substance kg )
10.3
define latent heat of vaporisation
amount of enery transferred to change a substance between the liquid and the gaseous sate, at a constant temperature
10.3
specific latent heat of vaporisation
amt of emnergy transferred per unit mass of a substance to change its state between the liquid and gaseous state, at a constant tempearture
Lv ( latent heat of vaporisation ) = lv ( specific latent heat of vaporisation J/kg ) * m ( mass of substance kg )
10.3
heating & cooling curve
heating : KE increase, PE increase ( with average speration of particles ), object expands
melting and boiling : KE unchanged ( temperature constant ) , PE increase
cooling : KE decrease, PE decrease ( with average seperation of particles, object contracts
condensation and solidification : KE unchanged ( temperature constant ), PE decreases
10.3
describe internal energy
internal energy = total KE of particles + total PE of particles
; internal energy of substance increase / decrease when heated / cooled
