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OCR Physics B Unit 4 > 4.4 Matter Very Simple > Flashcards

4.4 Matter Very Simple Flashcards

1
Q

Which temperature scale starts at absolute zero?

A

The Kelvin scale.

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2
Q

What happens at absolute zero?

A

All particles have minimum possible kinetic energy.

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3
Q

What is 0K in degrees Celsius?

A

-273.15ºC

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4
Q

Which temperature scale is used in thermal physics equations?

A

The Kelvin scale.

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5
Q

What is Boyle’s law?

A

At a constant temperature, the pressure and volume of a has are inversely proportional. pV = constant.

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6
Q

What is Charle’s law?

A

At a constant pressure, the volume of a gas is directly proportional to its absolute temperate. V/T = constant.

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7
Q

What is the Pressure law?

A

At a constant volume, the pressure of a gas is directly proportional to its absolute temperature. p/T = constant.

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8
Q

What equation do you get from combining the three gas laws?

A

pV/t = constant

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9
Q

What is the value of the molar has constant?

A

8.31 J mol^-1 K^-1

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10
Q

What is the ideal gas equation?

A

pV = nRT

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11
Q

What does n represent in the ideal gas equation?

A

The number of moles of gas present.

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12
Q

What is Avogadro’s constant, NA?

A

The mole of gas particles in one mole.

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13
Q

What is the value of Avogadro’s constant?

A

6.02 x 10^23

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14
Q

What is the Boltzmann’s constant equivalent to?

A

R / NA

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15
Q

What is the meaning of the Boltzmann’s constant?

A

The gas constant for one particle of gas.

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16
Q

What is the value of Boltzmann’s constant?

A

1.38 x 10^-23

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17
Q

What is the equation of state of an ideal gas?

A

pV = NkT

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18
Q

Using a cubic box analogy, explain why particle velocity is proportional to pressure.

A

The faster a particle is travelling, the more momentum is exchanged with the walls more frequently. This means a larger force on the wall and therefore a higher pressure.

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19
Q

Using a cubic box analogy, explain why the number of particles is proportional to pressure.

A

Each particle exerts a force on the wall as it hits it so total force is proportional to number of particles. This results in a higher pressure since P = F / A.

20
Q

Using a cubic box analogy, explain why the volume of the box is proportional to the pressure.

A

Describing the size of the box increases the rate of collisions and reduces the area of the walls. Hence a higher pressure.

21
Q

Why is mean square speed used?

A

To take into account the difference in particle velocities.

22
Q

Why is the mean square speed multiplied by one third?

A

Because there are 3 dimensions, it can be assumed that a third of all particles are moving in one dimension at a time.

23
Q

Give the third equation involving pV.

A

pV = 1/3 Nm(ć^2)

24
Q

What is r.m.s. speed?

A

Root mean square speed, the typical speed of a particle.

25
Q

Give four assumptions used in kinetic theory.

A

The gas contains a large number of particles. The particles move rapidly and randomly. The motion of the particles follows Newton’s Laws. Collisions between particles themselves and the container are perfectly elastic.

26
Q

What is a random walk of a particle?

A

A model of the movement of particles.

27
Q

What does a random walk involve?

A

Moving a step in a random direction repeatedly.

28
Q

What is the relationship between average distance moved after N steps and number of steps moved?

A

Distance is proportional to √N.

29
Q

What is the zeroth law of thermodynamics?

A

If body A and body B are both in thermal equilibrium with body C, body A and body B must be in thermal equilibrium with each other.

30
Q

Where does thermal energy flow to and from?

A

Regions of high temperature to low temperature.

31
Q

What is the definition of specific thermal capacity, c?

A

The amount of energy needed to raise the temperature of 1kg of a substance by 1K.

32
Q

Give the word equation for specific heat capacity.

A

energy change = mass x specific thermal capacity x change in temperature

33
Q

Give the symbol equation for specific heat capacity.

A

∆E = m c ∆θ

34
Q

What are the units of c, specific heat capacity?

A

J kg^-1 K^-1

35
Q

Describe the shape of the graph comparing proportion of particles with a given speed and particle speed.

A

A Maxwell-Boltzmann distribution curve.

36
Q

What happens to particle speeds as the temperature of a gas increases?

A

The average particle speed increase and the maximum particle speed increases. The means the speed distribution curve will be more spread out.

37
Q

What happens when gas particles collide?

A

Energy is transferred between the particles.

38
Q

When gas particles collide, some may particles may gain speed whilst others…

A

Slow down.

39
Q

Describe the speed of gas particles between collisions.

A

Constant.

40
Q

Give three assumptions used in kinetic theory.

A

There are no attractive forces between particles. Any forces that act during collisions are instantaneous. Particles have a negligible volume compared with the volume of the container.

41
Q

Despite the change in energy of individual particles as a result of collisions, the total energy of the system…

A

Is unchanged.

42
Q

The total energy of the system is constant so the average speed of the particles in the system will stay the same provided…

A

Temperature of the gas is constant.

43
Q

What the internal energy of a gas?

A

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

44
Q

What is average kinetic every of an individual particle proportional to?

A

Absolute temperature.

45
Q

Give the equation for average kinetic energy of an individual particle, 1/2 m ć^2

A

1/2 m ć^2 = 3/2 (n R T)/N

46
Q

Give the two equations used to derive the equation for average kinetic energy of an individual particle.

A

pV = 1/3 Nm(ć^2) and pV = nRT

OCR Physics B Unit 4 (5 decks)

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