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Thermal Physics Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

absolute zero

A

The lowest possible temperature that any object can theoretically
around -273(.15)
Given the value of 0 kelvins

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2
Q

How to calculate kelvin

A

K = C + 273

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3
Q

Internal energy

A

The internal energy of a body is the sum of the randomly distributed kinetic and potential energies of all its particles

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4
Q

As the temperature of the gas increases

A

-the average particles speed increases
- The average kinetic energy of the particles increases
- the distribution curve becomes more spread out

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5
Q

Specific heat capacity

A

The amount of energy needed to raise the temperature of 1kg of the substance by 1K (or 1 degree)

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6
Q

Specific heat capacity

A

The amount of energy needed to raise the temperature of 1kg of the substance by 1K (or 1 degree)

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7
Q

Specific heat capacity equation

A

Energy change = mass x specific heat capacity x change in temperature

Q = mc x (change in temp)

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8
Q

Specific latent heat

A

SLH of fusion or vaporisation is the quantity of thermal energy needed to be gained or lost to change the state of 1kg of a substance

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9
Q

Specific latent heat equation

A

Energy change = specific latent heat x mass of substance changed

Q = ml

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10
Q

Boyles law

A

At a constant temperature and the pressure and the volume of a gas are inversely proportional
For example, if you reduce the volume of a gas its parcel will often be closer together and collide of each other and the container more often so the pressure increases

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11
Q

Ideal gas

A

An ideal gas is a theoretical gas that obeys Boyles law at all temperatures
Boyles law means that at any given temperature the product of p and V will always be the same
pV = constant

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12
Q

Pressure and volume graph

A

The higher the temperature of the gas the further the curve is from the origin

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13
Q

Charles law

A

At a constant temperature and the volume V of a gas is directly proportional to its absolute temperature T
And ideal gas also obeys Charles law
V and T are directly proportional to
At the lowest theoretically possible temperature, the volume is zero
If Charles law is a bid the volume divided by the temperature is constant
V/T = constant
When you heat gas, the particles gain kinetic energy and move more quickly
At a constant pressure this means they move further apart and so the volume of the gas increases

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14
Q

The pressure law

A

At constant volume the pressure of an ideal gas is directly proportional to its absolute temperature
For example, if you heat a gas the particles gain kinetic energy this means they move faster
If the volume doesn’t change, the particles will collide with each other and their container more often and at high speeds, increasing the pressure inside the container
At absolute zero the pressure is also also zero
If the pressure law is a base the pressure divided by the temperature is constant
P/T = Constant

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15
Q

Relative molecular mass

A

The sum of the relative atomic masses of all the atoms making up a molecule

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16
Q

Mole

A

An amount of substance containing Na particles all of which are identical
Na is avogadro constant

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17
Q

Avogadro constant value

A

6.02 x 10^23 mol^-1

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18
Q

Avogadro constant

A

The number of particles in a mole
Defined as a number of atoms in exactly 12 g of carbon isotope

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19
Q

Molar mass

A

The molar mass of a substance is the mass that one mole of the substance would have,(usually in grams) and is equal to its relative atomic or relative molecular mass
For example, the molar mass of helium (RAM = 4) is 4 g

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20
Q

molar gas constant, R

A

pV/T
putting in the values for 1 mole of an ideal gas at room temperature and atmospheric pressure gives the value
8.31JK-1
gas constant for one mole of gas

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21
Q

ideal gas equation

A

pV/T = nR
R = molar gas constant
n = number of moles of gas

22
Q

boltzmann constant, k

A

k = R/Na
R = molar gas constant, 8.31
Na = avagadros constant

k = 1.38x10-23JK-1
gas constant for one mole of gas

23
Q

N

A

N = n x Na

24
Q
A

Nk = nR

25
Q

ideal gas equation for N molecules

A

pV =NkT

26
Q

work done equation

A

p x change in V

27
Q

work done

A

for a gas to expand or contract pressure, work must be done (i.e energy transfer, normallu heat transfer)
e.g. heat a gas filled ballon = expand, remove heat = contract back to original size as heat is transferred back to surroundings

area under graph = energy transferred

28
Q

change in momentum equation

A

mu-(-mu) = 2mu

29
Q

time between collision of object equation

A

2l/u

30
Q

number of coolisions per second equation

A

u/2l

31
Q

rate of change of momentum equation

A

2mu x u/2l = muu/l

32
Q

total force of all molecules on wall equation

A

F = m( u21 + u22 + etc.)/l

33
Q

mean u squared

A

u21 + u22 + etc. / N

34
Q

Total force with mean of u

A

F = Nm-u2 / l

35
Q

derive pressure with force equation

A

pressure = force / area

p = Nm-n2 / lll == /v

36
Q

same equation but intergrate c

A

if you treat all N molecules the same way, gives a mean square speed of -c2

-c2 = -v2 + -w2 + -u2

since molecules move randomly…

-v2 = -w2 = -u2

therefore -c2 = 3-u2

37
Q

pV using 3-u2

A

pV = 1/3 X Nm-c2

38
Q

-c2 mwaning

A

mean square speed of gas molecules in m2 s-2

39
Q

root mean square speed

A

if -c2 is the average of the sqaures of speed of molecules, the sqaure rooy would be the typical speed

r.m.s speed = root mean sqaure speed ( root -c2 == Crms

40
Q

Crms in pV equation

A

pV = 1/3 x Nm(Crms)^2

41
Q

expalining charles law and pressure law

A

temperature is related to Ke of the molecules, as temperature increases, average speed of molecules increases, means rate of change of momentum of molecules colliding with walls of container increases so force on container increases

42
Q

if volume is fixed, pressure change because

A
  1. more collisions between molecules and against wall in a given amount of time
  2. an average collision will result in larger change in momentum and exert a larger force on the wall
43
Q

if pressure is fixed, volume will change because…

A
  1. if volume is larger, there will be longer time between collisions, so rate of change of momentum and force on wall will reduce
  2. as volume increases, SA of walls increases, pressure = force per unit area so increase in area stops incraese in pressure
44
Q

Assumptions in kinetic theory

A
  • all molecules of gas are identical
    -gas contains large number of molecules
    -molecules have negligable volume com pared with volume of container, acts as point masses
    -molecules continually move randomly
    -newtonian mechanics apply
  • collisions are elastic (Ke conserved)
    -molecules m ove in straight lines after collisions
    -forces that act during collision for less time than between collisions

A gas obeying these assumptions = ideal gas

45
Q

assumption of internal energy for an ideal gas

A

For an ideal gas you assume all internal energy is in the form of Ke
means you can use the product of pV to find average and total Ke

46
Q

combing equations

A

1/3 Nm (Crms)^2 = nRT

3/2 X 1/3 Nm(Crms)^2 = 3/2 x nRT

1/2 m(Crms)^2 = 3/2 nRT / N

sub Nk for nR
3/2 X NkT / N

1/2 m(Crms)^2 = 3/2 x kT

K = R/Na
1/2 m(Crms)^2 = 3/2 x RT / Na

47
Q

emprical laws

A

laws based on observations and evidence
they can predict what will happen but cant explain why

48
Q

kinetic theory

A

based on a theory
means its based on assumptions and derivations from knowledge and theories we already had and will both predict and explain why a change occurs

49
Q

develpment of gas laws

A

Ancient Greek and Roman philosiphers had ideas about gas 2000 years ago

Robert Boyle discovered the relationship between pressure and volume at a constant temoeratire in 1662
Jacques Charles discovered volume is proportional to temperature at a constant pressure in 1787
Guillaume Atomons in 1699 noticed at a constant volume, pressure is proportional to temperature
in 1827 robert brown discovered brownian motion

50
Q

Brownian motion

A

Rober brown noticed pollen grains moved in water in a zig zag
this type of movemnt of any particles suspended in a fluid is known as brownian motion

51
Q

brwnian motion einstein

A

Einstein shown brownian motion supported kinetic theory model of different states of matter and that the random motion is due to the collisions with fast, randomly moving particles in a fluid

52
Q

brownian motion smoke example

A

can see brownian motion when large heavy particles like smoke move with brownian motion by smaller lighter particles like air travelling at high speeds
this is evidence that air is made up of tiny atoms moving really quickly

Physics (11 decks)

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