Chapter 13 - gas laws Flashcards by amy packwood

What is the lowest possible temperature called?

Absolute zero

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What are the units of the absolute temperature scale?

Kelvin

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What is absolute zero in kelvin?

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What is absolute zero in °C?

-273°C

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What is the symbol for kelvin?

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What is the kinetic energy of particles at zero kelvin?

The minimum possible energy

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What does a change of one K equal in °C?

A change of one °C

one degree in kelvin = one degree in °C

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What units do all equations in thermal physics use?

kelvin, K

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How do you convert from °C to kelvin?

Add 273

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How do you convert from kelvin to °C?

subtract 273

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What is Boyle’s law?

At a constant temperature, the pressure of a gas is inversely proportional to its volume

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What is Charles’ law?

At a constant pressure, the volume of a gas is directly proportional to its absolute teperature

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What is the pressure law?

At a constant volume, the pressure of a gas is directly proportional to its absolute temperature

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What are the three gas laws as equations?

p = k/V
V = kT
p = kT

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What is the ideal gas equation?

pV = nRT

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When does a real gas approximate an ideal gas (so that the ideal gas equation can be used) ?

At low pressure and high temperature

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What is the amount of gas measured in?

moles

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What is the symbol for number of moles?

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What is R?

The molar gas constant

8.31

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What are the units of the molar gas constant?

Jmol^-1K^-1

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What is k?

Boltzmann’s constant

1.38 x10^-23

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What are the units of Boltzmann’s constant, K?

JK^-1

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How could Boltzmann’s constant be described?

The molar gas constant for one particle of gas

as R is the gas constant for one mole of gas

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What is Boltzmann’s constant equivalent to?

R/NA

NA = avagadro’s number

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What is Avagadro's number?

The number of particles in one mole of gas | 6.02 x10^23

What is the symbol for Avagadro's number?

NA | with subscript A

What is N?

The number of particles in a particular mass of gas

What is the equation for the number of particles in a mass of gas?

N = nNa | number of moles x avagadro's number

What is the equation of state?

pV = NKT

What is kinetic theory used for?

Explaining the gas laws on a microscopic level by modelling particles as hard balls which obey Newton's laws

Why is particle velocity proportional to pressure?

A faster particle has a larger momentum A larger momentum means a larger impulse force on the wall pressure is proportional to force, so pressure is greater + a higher velocity means less time taken to travel across the container, so more collisions and more force total

Why is number of particles, N, proportional to pressure?

More particles means more collisions, so a greater total force and a greater pressure

Why is the volume of the container inversely proportional to pressure?

A smaller container means less distance to travel between the walls, so a shorter travel time and more collisions More collisions per second means a larger total force and a greater pressure + a lower volume means sides have a lower area. pressure = force/area so the same force on a smaller area means a greater pressure

How do gas particles travel?

In random directions at different speeds

How many particles can be estimated to be travelling in one dimension (x/y/z) at any given time?

a third

What is the mean square speed?

The mean average of the squares of the velocities

How is mean square speed represented?

c^2 with a bar on top

What is the gas equation using mean square speed? | What does m represent in this equation?

``` pV = 1/3Nm(mean square speed) m = the mass of one particle ```

What is the root mean square speed?

The typical speed of particles | the root of the mean of the squared velocities

How is root mean speed commonly written?

r.m.s speed

What are the units of the mean square speed?

m^2s^-2

What are the seven assumptions made about gases in kinetic theory?

- There is a large number of particles - Particle move rapidly and randomly (no preferential motion, no fields) - Particles obey Newton's laws - Collisions between particles and walls are, on average, perfectly elastic - No attractive forces between particles - Any forces which act during collisions are instantaneous - Particles have a negligible volume compared to the volume of the container

What is a gas which obeys all assumptions called?

An ideal gas

How is the motion of a single gas particle modeled?

With a RANDOM WALK | The particle starts in one place, moves N steps in random directions, and ends up somewhere else

What causes a particle to change direction during a random walk?

collisions with other particles

What is the distance moved on a random walk proportional to?

the square root of the total number of steps

What is the symbol for the number of steps in a random walk?

How far can a gas particle usually move per step of a random walk (ie distance traveled between collisions)?

10^-7 m

What is the thermodynamic scale?

The temperature scale in kelvin

From what regions is thermal energy transferred to and from?

Always from areas of higher thermal energy to areas of lower thermal energy

When will the exchange of thermal energy stop?

When thermal equilibrium is reached | All regions have the same thermal energy (all at the same temperature) so the net flow of energy stops

What is a rule of thermal equilibrium?

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

What is specific thermal capacity?

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

What is the symbol for specific thermal capacity?

What is the formula for change in thermal energy?

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

What is Δθ?

Change in temperature in K or °C

What are the units of c?

Jkg^-1K^-1 or Jkg^-1°C^-1

What does the speed distribution of gas particles depend on?

The temperature of the gas

What happens to the speed of gas particles as the temperature increases?

- Average particle speed increases - maximum particle speed increases - The speed distribution curve becomes more spread out (flatter)

What is internal energy?

The total energy of a system

What is the formula for internal energy?

kinetic energy of particle + potential energy of particles

How is total kinetic energy of particles in a gas found?

Taking the average kinetic energy and multiplying it by the number of particles

What is the formula for the average kinetic energy of an individual particle in a gas?

1/2m(mean square speed) | 1/2 x m x v^2

What is the equation for the average kinetic energy of a gas particle?

1/2m(mean square speed) = 3nRT/2N

What affect on the energy will a rise in absolute temperature have on a gas?

The kinetic energy will increase and so the internal (total) energy will increase

Chapter 13 - gas laws Flashcards

(65 cards)