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physics content ocr a > thermal physics > Flashcards

thermal physics Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

describe the structure of a solid

A

particles are fixed in a uniform lattice, where particles vibrate around their fixed positions
they are held in position by strong forces of electrostatic attraction

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2
Q

describe the structure of a liquid

A

particles are not fixed in position: they are constantly moving around but there are still some forces of attraction

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3
Q

describe the structure of a gas

A

particles are free to move around with constant random motion. there are no forces of attraction between particles in an ideal gas

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4
Q

define thermal equilibrium

A

no net transfer of energy; two bodies in thermal equilibrium have the same temperature

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5
Q

what is the celsius scale?

A

uses the freezing + boiling points of water to make a temperature scale

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6
Q

what is the kelvin scale?

A

also the thermodynamic scale does not depend on the properties of the substance

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7
Q

what value is absolute zero in degrees?

A

-273 degrees

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8
Q

convert degrees to kelvin

A

+273

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9
Q

what occurs when you heat a solid?

A

particles gain kinetic energy and vibrate more vigorously
eventually they may break away from the structure + become free to move around
when this happens, the solid has melted into a liquid

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10
Q

what occurs when you heat a liquid?

A

some of the particles gain enough energy to break away from other particles
particles that escape from the body of the liquid become a gas

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11
Q

what occurs when you heat a gas?

A

molecules collide with the container- these collisions are responsible for pressure which a gas exerts on the container

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12
Q

what is brownian motion?

A

particles move with random, zig zag motion

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13
Q

how could we observe Brownian motion?

A

put smoke in a brightly illuminated glass jar and observe particles using a microscope
smoke particles appear as bright specs moving haphazardly from side to side

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14
Q

how did Einstein prove the existence of atoms and molecules in the air?

A

randomly moving particles were hitting the smoke particles unevenly, causing this motion

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15
Q

define internal energy

A

the sum of the kinetic and potential energy of particles within a system

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16
Q

what is the relationship between kinetic energy and temperature?

A

directly proportional

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17
Q

what is potential energy caused by?

A

interactions between particles and is based on positions relative to each other

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18
Q

what happens to a substance when it’s heated?

A

temperature increases so kinetic energy increases and the internal energy increases

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19
Q

what happens when a substance changes phase?

A

the energy from the heat is used to alter and break the bonds within the substance but not to raise the temperature. as a result, the kinetic energy of the substance remains the same but the internal energy changes in order for it to change phase

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20
Q

define specific heat capacity

A

the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree or 1 kelvin

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21
Q

give the equation for specific heat capacity

A

E= mcT

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22
Q

how could you measure the specific heat capacity of a solid or a liquid?

A

heat substance with a heater until there is a temperature change of 10K, recording the time taken to do this
attach an ammeter and voltmeter to heater to work out energy supplied using E=VIt
rearrange specific heat capacity equation to calculate c

23
Q

define the specific latent heat of fusion

A

the amount of energy needed to melt or freeze 1kg of a substance

24
Q

define the specific latent heat of vaporisation

A

the amount of energy needed to boil or condense 1kg of a substance

25
Q

what is the equation for specific latent heat?

A

E=mL

26
Q

how could you measure the specific latent heat of a solid or liquid?

A

place a heating coil and equal masses of ice in 2 funnels above the beakers
turn on one heating coil for 3 mins- record energy transferred
after 3 mins, measure the mass of water collected in beakers. subtract one from the other to get the mass of ice that melted solely due to presence of heater
use L= E/m to find slh

27
Q

what 3 laws does an ideal gas obey?

A

Boyle’s law
Charles’ law
pressure law

28
Q

what is Boyle’s law? give any supporting equations

A

at a CONSTANT TEMPERATURE, the pressure and volume of a gas are inversely proportional
higher temp= further curve from the origin
pV=constant

29
Q

what is the pressure law? give any supporting equations

A

at a CONSTANT VOLUME, the pressure of a gas is directly proportional to temperature. P/T= constant

30
Q

what is Charles’ law?

A

at a CONSTANT PRESSURE, the volume of a gas is directly proportional to its absolute temperature

31
Q

what equation is given when you combine all 3 gas laws?

A

PV/T= constant

32
Q

what is the gas constant?

A

8.31 J/mol/K

33
Q

what is the ideal gas equation?

A

pV=nRT

34
Q

what is Avogadro’s constant?

A

6.02x10^23

35
Q

what equation can be used to find the number of particles?

A

N = n x Na

36
Q

what equation can be used to find the Boltzmann constant?

A

k= R/Na

37
Q

how can you get the equation pV=nKT

A

combine N = n Na and K = R/Na
Nk=nR
substitute into pV=nRT
to get pV=nKT

38
Q

what is the Boltzmann constant?

A

1.38x10^-23 J/K

39
Q

describe the motion of a gas in a container

A
  • particles of the gas are free to move around with constant random motion
  • there are no forces of attraction according to Newton’s 1st law
  • they continue to move with constant velocity until they collide with another particle
40
Q

what happens when a particle collides with a wall of a container?

A

a force is exerted on the box
the box exerts an equal and opposite force
Newton’s 3rd law

41
Q

how can you calculate the force exerted by a particle on the wall of a container?

A 
-using Newton's second law
F= rate of change in momentum
p=mu
rebound = -mu
so change in momentum=2mu
forces by one particle = mass x velocity
42
Q

describe how pressure arises from gases in a container

A
  • the combined force from many particles is much larger, so lots of particles will be colliding with each wall at any given moment
  • motion is random, collisions will be spread all over the surface of each wall
  • result is a steady, even force on all walls of the box= pressure
43
Q

give an equation found when combining kinetic energy and the ideal gas equation

A

pV=1/3Nmc^2

44
Q

describe the effect of increasing volume

A

frequency of collision decreases as particles have further to travel between collisions
this decreases pressure

45
Q

describe the effect of increasing the number of particles

A

increases the frequency of collisions between particles and container
this increases the pressure

46
Q

describe the effect of increasing mass

A

greater force is exerted on the walls of the container (F=ma)
greater pressure

47
Q

describe the effect of increasing speed

A

greater change in momentum as p=mv
this means a greater force is exerted
F= change in momentum over time

48
Q

give the assumptions of the kinetic theory

A
  • gas contains a large number of particles
  • particles move rapidly + randomly
  • collisions are perfectly elastic
  • volume of particles in negligible when compared to the volume of the gas
  • no forces between particles except in a collision
  • length of time involved in a collision is negligible compared to time between collision
49
Q

what name is given to a gas that obeys all assumptions of the kinetic theory?

A

an ideal gas

50
Q

what does the Maxwell-Boltzmann distribution show?

A

it shows how the speeds of molecules are distributed in an ideal gas

51
Q

as the temperature of a gas increases, what effect does it have on an ideal gas?

A

the average particle speed increases
the maximum particle speed increases
the distribution curve is more spread out
as a result of collisions, energy will be transferred between particles
some particles will gain speed in a collision whereas others will slow down

52
Q

between collisions, how would you describe the speed of the particles?

A

they travel at constant speed

53
Q

what equation is created when equating 1/3Nmc^2=NkT?

A

E=3/2kT

54
Q

what is the relationship between average kinetic energy and internal energy to the absolute temperature?

A

directly proportional
a rise in absolute temperature will cause an increase in the kinetic energy of the particles, meaning a rise in internal energy

physics content ocr a (4 decks)

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