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A LEVEL PHYSICS > thermal save my exams > Flashcards

thermal save my exams Flashcards

1
Q

what is meant by the internal energy of a substance

A
  • the sum of the randomly distributed kinetic and potential energies of the particles in a body
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2
Q

what is meant by randomly distributed?

A
  • they all have different speeds and seperations
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3
Q

what is the internal energy of a system determined by?

A
  • temperature
  • random motion of molecules
  • phase of matter
  • intermolecular interactions between the particles
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4
Q

how can the internal energy of a system be increased ?

A
  • doing work on it
  • adding thermal energy to it
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5
Q

how can the internal energy of a system be decreased?

A
  • losing thermal energy to its surroundings
  • system doing work on its surroundings
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6
Q

what is the first law of thermodynamics?

A
  • the internal energy of a system is increased when thermal energy is transferred to it or when work is done on it
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7
Q

what happens when a gas expands?

A
  • volume increases
  • work is done BY the gas ON the surroundings
  • this decreases internal energy
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8
Q

what happens when a gas is compressed?

A
  • volume decreases
  • work is done ON the gas BY the surroundings
  • this increases internal energy
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9
Q

what happens when a piston moves down?

assume insulated

A
  • space occupied by the gas molecules is compressed
  • work is transferred to the systems internal energy
  • increasing internal energy of the gas
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10
Q

what happens when a piston moves up?

A
  • space occupied by the gas molecules expands
  • work is transferred from the systems internal energy
  • decreases internal energy of the gas
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11
Q

what is specific heat capacity of a substance?

A
  • the amount of thermal energy required to raise the temperature of 1kg of a substance by 1K/1*C without changing its state
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12
Q

what are two deductions we can make from specific heat capacity?

A
  • the heavier the material the more energy required to raise its temperature
  • the larger change in temperature, the higher thermal energy required
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13
Q

how can thermal energy be calculated?

A

^Q = mc^T

^Q = change in thermal energy ( J )
m = mass of the substance you are heating
c = specific heat capscity of the substance
^T = change in temperature

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14
Q

what is latent heat capacity?

A
  • the thermal energy required to change the state of 1kg of a substance without changing its temperature
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15
Q

what is the specific latent heat of fusion?

A
  • the thermal energy required to convert 1kg of a solid to liquid with no change in temperature
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16
Q

what is the specific latent heat of vaporisation?

A
  • the thermal energy required to convert 1kg of a liquid to gas with no change in temperature
17
Q

what is the equation to calculate the energy required to melt/vaporise a mass m

A

Q = m L

Q = thermal energy
m = mass
L = specific latent heat of fusion / vaporisation

18
Q

why is the latent heat of vaporisation much greather than the latent heat of fusion?

A
  • more energy has to be supplied to seperate molecules, thank break a solid bond
  • intermolecular forces are important
19
Q

what happens at thermal equilibrium?

A
  • both have same final temperature
20
Q

what happens when a substance is heated?

A
  • molecules are given energy in the form of kinetic and potential energy
21
Q

what happens during a change of state?

A
  • no change in temperature
  • potential energies of molecules change, but not kinetic energies
22
Q

why do molecules have potential energies?

A
  • due to their seperation of intermolecular bonds, moving further apart of closer together.
23
Q

what is absolute zero?

A
  • the temperature at which the molecules in a substance have zero kinetic energy
24
Q

how do you convert to K and vice versa

A

• + 273 = K
• = K - 273

25
Q

what is Boyle’s Law?

A
  • if temperature is constant

pressure is inversely proportional to volume

p1v1 = p2v2

26
Q

what is Charles Law?

A
  • if pressure is constant

volume is directly proportional to temperature

v1/t1 = v2/t2

27
Q

what is the Pressure Law?

A
  • if volume is constant

pressure is directly proportional to temperature

p1/t1 = p2/t2

28
Q

what do ideal gases obey?

A

pV directly proportional to temperature

29
Q

why does higher temp lead to higher pressure?

A
  • temperature is a measure of the average kinetic energies of molecules ( speed )
  • higher temperatures cause higher speeds, hence molecules collide with the surface of the wall more frequently
  • faster the molecules, greater the force due to momentum

pressure increases as P = force per unit area

30
Q

what can we assume with ideal gas equations?

A
  • collisions are elastic
  • has molecules with negligible volume
  • obeys Gas laws
  • has no interactions between the molecules

A LEVEL PHYSICS (14 decks)

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