Thermal physics

Absolute Zero

The lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy.

Explain why when there is a great speed, the temperature will be greater

Avogadro Constant

The number of particles that make up one mole of any gas.

Boltzmann Constant

A constant relating the average kinetic energy of the particles in a gas, to the gas’ temperature.

Boyle’s Law

The pressure of an ideal gas is inversely proportional to its volumewhen held at constant temperature.

Brownian Motion

The random motion of particles.

Charles’ Law

The volume of an ideal gas is directly proportional to its absolute temperature when held at constant pressure.

Ideal Gas

A gas that meets the ideal gas assumptions. All the gas laws are based on ideal gases.

Internal Energy

The sum of the randomly distributed kinetic and potential energies of the particles in a given system.

Kelvin Scale

An absolute temperature scale that starts at absolute zero (0 K = -273 °C).

Molar Gas Constant

A fundamental constant, used in the ideal gas law.

Molar Mass

The mass of one mole of the substance in question.

Molecular Mass

The mass of one molecule of the substance in question.

Pressure Law

The pressure of an ideal gas is directly proportional to its absolute temperature, when the volume is fixed.

Specific Heat Capacity

The amount of energy required to increase the temperature of 1 kg of a substance by 1 Kelvin.

Specific Latent Heat

The amount of energy required to change the state of 1kg

of a substance without a change of temperature.

State Changes

During a state change, the potential energy of the system is changing but the kinetic energy is not.

Two forms of specific latent heat.

1. Specific latent heat of fusion

2. Specific latent heat of vaporisation

Specific latent heat of fusion

Used for the transition between solid and liquid.

Specific latent heat of vaporisation

Used for the transition between liquid and gas.

Boyle’s law

Boyle’s law links the pressure and volume of a gas. It states that as volume decreases, the pressure on a gas at constant temperature increases. This can be expressed in equation form:

pV = Constant

Charles’ law

Charles’ law links the temperature and volume of a gas. It states that as temperature increases, the volume of a gas at constant pressure increases. This can be expressed in equation form:

V/t = Constant

Pressure law

The pressure law links the temperature and pressure of a gas. It states that as temperature increases, the pressure of a gas of constant volume increases. This can be expressed in equation form:

p/t = Constant

Internal energy

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

The internal energy of a system can be increased in two ways.

1. Do work.

2. Increase the temperature.

Do work

Do work on the system to transfer energy to it, (e.g moving its particles/changing its shape).

Increase the temperature

Increase the temperature of the system.

Gas laws

The gas laws describe the experimental relationship between pressure (p), volume (V), and temperature (T) for a fixed mass of gas.

Three gas law.

1. Boyle’s Law

2. Charles’ Law

3. The Pressure Law

Boyle’s Law

When temperature is constant, pressure and volume are inversely proportional

Charles’ Law

When pressure is constant, volume is directly proportional to absolute temperature.

The Pressure Law

When volume is constant, pressure is directly proportional to absolute temperature.

Absolute zero

Absolute zero (- 273 °C ), also known as 0 K, is the lowest possible temperature, and is the temperature at which particles have no kinetic energy and the volume and pressure of a gas are zero.

Molar mass

Molar mass is the mass (in grams) of one mole of a substance and can be found by finding the relative molecular mass, which is (approximately) equal to the sum of the nucleons in a molecule of the substance.

Brownian motion

Brownian motion is the random motion of larger particles in a fluid caused by collisions with surrounding particles, and can be observed through looking at smoke particles under a microscope.

What is internal energy?

The sum of the potential and kinetic energies of a system.

How can you increase the thermal energy of a system?

We can increase it by heating it up or doing work on the object.

Explain the energy changes that occur during a change of state.

During change of state the potential energy of the particles change but the kinetic energies doesn’t change.

What equation can be used to determine the energy required to change the temperature of a substance?

Q = mcΔT

Give the equation to work of the energy for change of state ?

Q = ml

What is the Ideal gas equation?

pV = nRT

where;

p is a pressure in unit Pa.

V is a volume in unit m^3.

R is the Molar Gas constant, 8.314 J/mol·K.

n is the number of mols.

T is the temperature in unit Kelvin.

What is the first law of thermodynamics?

ΔU = Q - W

Where;

Q is the heat added to a system.

W is the work done by the system.

What is the specific heat capacity of substance?

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

What is the specific latent heat of a substance?

The energy required to change the state per unit mass of a substance, while keeping the temperature constant.

What is an ideal gas?

A gas that:

● The gas molecules don’t interact with each other.

● The molecules are thought to be perfectly spheres.

What is the internal energy of an ideal gas equal to?

It is equal to the internal energy of an ideal gas

What is Boyle’s law?

Pressure is inversely proportional to volume, providing temperature is constant.

In an ideal gas,how would increasing the volume change the temperature of the gas, while the pressure remains constant?

As you increase the volume, you also increase the temperature.

Explain how increasing the temperature of a balloon, while keeping the volume the same will increase the pressure.

● As the temperature increases, the average kinetic energy increases.

● Therefore the particles are travelling at a higher speed on average

● There are also more frequent collisions

● Which means the particles would exert a greater force

● Which would cause a increased rate of change of momentum

● Therefore increasing pressure.

What is absolute zero?

At - 273 ℃. This is where objects have no/minimum kinetic energy.

What is Avogadro’s constant? (in words)

The number of atoms there are in one mole of a substance.

True or false: ‘All collisions between particles and between particles and the wall are elastic’ is an assumption of an ideal gas?

True.

State an assumption of an ideal gas related to time?

The time for each collisions is negligible in comparison to the time take between collisions.

Describe 3 other assumptions of the ideal gas equation.

Three (3) of the following:

● The particles move randomly.

● They follow Newton's laws of motion.

● No intermolecular forces act between particles.

● Volume of the particles is negligible compared to the volume of the container they are in.

What is meant by the root mean square speed?

The square root of the mean of the squares of the speeds of the molecules.

What is Brownian motion?

Brownian motion is the idea that very small objects have random motion in a liquid or gas due to random bombardment by the molecules in this substance. This movement will be fractionally more on one side than the other so a force will push it for an instant as the net forces shifts directions. This random motion is Brownian Motion and gives evidence for the existence of atoms.