thermal properties of matter

Question 1

si unit of internal energy & thermal energy

Answer 1

joule(J)

Question 2

internal energy is made up of?

Answer 2

internal KE(due to motion of particles, directly related to temp,highr the temp more vigorous the motion of partciles) and internal PE(due to stretching n compression of intermolecular bonds as particles move, amt of potential energy stored in the bonds depend on force btwn the particles & how far apart thy r)

Question 3

heat capacity definition

Answer 3

(C) amount of thermal energy req to raise the temp of a substance by 1K or 1*C
depends on mass n material!

Question 4

formula for heat capacity

Answer 4

Q = C delta thetha

Question 5

formula for specific heat capacity

Answer 5

Q =mc delta thetha

Question 6

specific heat capacity definiton

Answer 6

(c) amount of thermal energy required to raise the temp of a unit mass(1kg) of a substance by 1*C/1K
more shc–> more time taken

Question 7

definition of melting

Answer 7

its a process in which a substance changes its state from solid to liquid, w/o a change in temp

Question 8

what happens during melting?

Answer 8

solid-> held tghtr by strong bonds-> closely packed tgthr-> internal PE of a solid is lesser than a liq-> thermal energy absorbed is used to brk the strong bonds btwn the particles-> can now move abt their fixed positions-> further apart-> change of state
LATENT HEAT OF FUSION

Question 9

definition of solidification

Answer 9

its a process in which a substance changes its state from liquid to solid, w/o a change in temp

Question 10

what happens during solidification?

Answer 10

energy is released as gas forms bond with each other to form solid-> the internal PE decreases, KE remains constant which is why thr is no change in temp n the particles now no longer move abt freely but rathr move abt their fixed positions

Question 11

definition of boiling

Answer 11

its a process in which a substance absorbs thermal energy to change its state from liquid to gas, at a fixed temp

Question 12

what happens during boiling?

Answer 12

thermal energy supplied–> used to seperate the water molecules–> provide energy for the molecules to push bck on the surrounding atm so as to escape into air
LATENT HEAT OF VAPORISATION: thermal energy tht is absorbed to change liq to gaseous state, w/o a change in temp
so now the water molecules r FURTHER APART-> increase in volume w a negligble intm bonds btwn thm so water has changed state

Question 13

definition of condensation

Answer 13

is the change of state of a substance frm a gas to a liq, @ a fixed temp

Question 14

what happens during condensation?

Answer 14

thermal energy supplied-> used to form the bonds btwn the particles, thermal energy is released in the process and now particles are held closer together n they are able to slide past each other, PE decrease
LATENT HEAT OF VAPORISATION

Question 15

definitions of latent heat & SI unit

Answer 15

is the energy released or absorbed by a substance during a change of state, w/o a change in its temp
si unit: Joules(J)

Question 16

define latent heat of fusion(Lf)

Answer 16

for MELTING N SOLIDIFICATION!
is the amt of thermal energy req to change a substance frm solid to liq state or vice versa, w/o a change in temp
depends on mass n material

Question 17

define latent heat of vaporisation(Lv)

Answer 17

for BOILING N CONDENSATION!
is the amt of thermal energy req to change a substance frm liq to gas or vice versa, w/o a change in temp
depends on mass n material

Question 18

define specific latent heat of fusion
&formula
&SI unit

Answer 18

(l f) is the amt of thermal energy req to change unit mass(1kg) of the substance frm solid to liq state or vice versa, w/o a change in temp
formula: Lf=mlf
si unit: J/kg

Question 19

define specific latent heat of vaporisation
& formula
&si unit

Answer 19

(l v) is the amt of thermal energy req to change unit mass(1kg) of the substance frm liq to gas state or vice versa, w/o a change in temp
formula: Lv=mlv
si unit: J/kg

Question 20

define evaporation

Answer 20

is the process whereby the water changes intp vapor below its boiling point

Question 21

difference btwn boiling n evaporation

Answer 21

B got bubbles, E no bubbles
B can only occur at a definite temp but E can occur at any temp
B is relatively fast, E relatively slow
B takes place thruout obj, E only at liq surface
B temp remains constant, E temp changes
B ext thermal energy source req, E no need

Question 22

similarity btwn boiling n evaporation

Answer 22

both hv same change of state & req latent heat of vaporisation

Question 23

how does evaporation work?

Answer 23

molecules in liq-> always moving rnadonly at diff speeds(diff ke)-> at the surface-> liq molecules tht hv enough energy to overcome the downward attractive forces of othr liq molecules & atm pressure-> escape into the atm-> the avg temp of liq decrease

Question 24

cooling by evaporation

Answer 24

whn the particles r in continous motion at diff speeds-> avg ke of particles increase-> temp of liq increase too n vice versa-> occurs whn fast-moving particles escape frm the surface of the liq, leavibg behind Prticles w lower KE-> lower temp since av ke remianing in liq decreases

Question 25

rate of evaporation is affected by

Answer 25

increased temp
reduced atm pressure 
increased movement of air
lower bp of liquid
larger exposed surface area
low humidity

Question 26

applications of evaporation

Answer 26

water evaporating frm skin etc