ch19 - thermal physics

Question 1

kinetic model ofnmatter

Answer 1

used to describe structural e of solids, liquids and gases

describes behaviour of matter in terms of moving particles

Question 2

solid

Answer 2

. molecules close together
. tightly bonded to neighbours
. vibrating about fixed positions

Question 3

gas

Answer 3

. particles broken free from their neighbours
. widely seperated
. free to move within container

Question 4

in change of state, temperature

Answer 4

is constant

Question 5

even in constant temperature part of graph

Answer 5

energy is still being lost

Question 6

more particles movement speed

Answer 6

more kinetic energy

Question 7

more particles disorder

Answer 7

more electric potential energy

Question 8

electric potential energy

Answer 8

. close, value is large and negative
. more distance, more potential energy
. complete seperation, potential energy is maximum and zero

Question 9

change of state (flat part)

Answer 9

. must be energy input
. temperature doesn’t not change
. molecules breaking free of one another
. increasing potential energy

Question 10

between the change of state (tilted part)

Answer 10

. input energy increases temperature
. molecules move faster
. kinetic energy increasing

Question 11

latent heat

Answer 11

latent = hidden

energy that goes towards breaking bonds between neighboring molecules, doesn’t cause a temperature change

Question 12

at change of state

Answer 12

no change in kinetic energy
no change in temperature

Question 13

melting takes less energy than boiling

Answer 13

in liquid boiling, almost all molecules have to be broken free

Question 14

evaporation

Answer 14

the process by which a liquid becomes a gas at a temperature below its boiling point

Question 15

cooling effect of evaporated liquid

Answer 15

. most energetic molecules escape
. avergae kinetic energy of remaining molecules is less
. less temperature

Question 16

internal energy

Answer 16

the sum of the random distribution of kinetic and potential energies of the atoms or molecules in a system

Question 17

ways of increasing the internal energy

Answer 17

. heating a gas - molecules vibrate more, molecules kinetic energy increases

. doing work on a gas - molecules strike and bounce off wall faster, more kinetic energy

. passing electric current through gas

Question 19

ways of decreasing internal energy of gas

Answer 19

. loses heat ti surroundings
. expands so work is done on surroundings

Question 20

first law of thermodynamics

Answer 20

<>U = q + W

the increase in internal energy of a body is equal ti the thermal energy transferred to it by heating plus the mechanical work done on it

Question 21

<>U = q + W

Answer 21

first law of thermodynamics

. q is energy supplied TO thr system by heating
. W is work done ON the system

Question 22

<>U

Answer 22

. postive value = internal energy increases = heat added TO the system = work done ON system

. negative value = internal energy decreases = heat taken AWAY from system = work done BY system

Question 23

in heat is added to system

Answer 23

W = 0 in <>U = q + W

Question 24

gas expands

Answer 24

work done on surroundings

Question 25

W = p<>V

Answer 25

F = pA W = pAs W = p<>V work done when the volume of a gas changes at constant pressure

Question 26

<>U = q + W for compressing gas

Answer 26

. don't allow heat to enter or leave a system - push piston fast, insulate the syringe . constant temperature - push piston very slowly

Question 27

thermal energy transferred from

Answer 27

high to low temperature region

Question 28

thermometer tells you

Answer 28

its own temperature

Question 29

thermal energy

Answer 29

energy transferred from ine object to another because of a temperature difference

Question 30

thermal equilibrium

Answer 30

a condition when two or more objects have the same temperature so that there is no net flow of energy between them

Question 31

thermodynamic scale

Answer 31

a temperature scale in which temperature is measured in Kelvin

Question 32

absolute zero

Answer 32

the temperature, 0K, at ehich a system has minimum internal energy (0 kinetic energy) = -273.15°C

Question 33

at absolute zero, it is impossible to

Answer 33

remove any energy from the particles

Question 34

K to °C

Answer 34

+273.15

Question 35

thermodynamic temperature scale is

Answer 35

. absolute - is not affected by any property of the substance like boiling point . only certain at fixed points

Question 36

fixed points of kelvin scale

Answer 36

. absolute zero, 0K . triple point of water, 273.16K (temperature at which ice, water and vapour can coexist)

Question 37

gap between absolute zero and triple point is divided into

Answer 37

273.16 equal divisions

Question 38

properties used on basis of thermometer include

Answer 38

. expansion of liquid column (liquid in glass thermometer) . resistance or electrical resistor/thermistor . emf produced by thermocouple . colour of electrically heated wire . volume of fixed mass at constant pressure

Question 39

thermometer must be calibrated at

Answer 39

two or more known temperatures, scale divided equally

Question 40

resistance and temperature

Answer 40

. metals = res increase, temp increase . thermistor = res increases fast, temp increases slow

Question 41

thermocouple

Answer 41

a device consisting of wires of two different metals across which an emf is produced when the two junctions of the wires are at different temperatures more emf = more temperature

Question 42

linearity

Answer 42

how accurate

Question 43

specific heat capacity

Answer 43

the energy required by unit mass per unit temperature change

Question 44

E = mc<>T

Question 45

resistance vs thermocouple thermometer

Answer 45

resistance . very robust . thermistor is narrow range . resistance wire is wide range . larger size than thermocouple, slow . thermistor is highly sensitive . resistance wire is less sensitive . thermistor fairly linear over narrow range . resistance wire has good linearity . can be operated from distance thermocouple . robust . can have wide range . smaller size than resistance thermometers, fast . can be sensitive . non linear . can be operated from a distance

Question 46

to heat a material, amount of energy required depends on

Answer 46

. mass of material . material itself . temperature change wished to achieve

Question 47

specific heat capacity

Answer 47

J kg-1K-1

Question 48

specific latent heat of fusion

Answer 48

the amount of heat energy needed per unit mass to convert unit mass of solid to liquid without change in temperature

Question 49

specific latent heat of vaporisation

Answer 49

the amount of heat energy needed per unit mass to convert unit mass of liquid to has without change in temperature

Question 50

E = mL

Answer 50

L is in Jkg-1

Question 51

specifc later heat of fusion of water

Answer 51

330kJ kg-1

Question 52

specific later heat of vaporisation of water

Answer 52

2.2MJ kg-1