Thermal Energy - LeFonch

Temperature (K) is directly proportional to the average random translational kinetic energy of particles in a gas.

A phase change represents a change in particle behavior arising from a change in energy at constant temperature.
A thermal energy transfer occurs whenever there is a difference in temperature between two bodies.
Thermal energy is always transferred from an aera of higher temperature to an area of lower temperature, until thermal equilibrium is reached.

However, the graph above shows that sometimes transferred thermal energy doesn't cause an increase in temperature.
Instead, it causes the material to change its phase.
Once the phase changes, the material continues to heat up as normal.

The internal energy of a substance is the total amount of kinetic energy and potential energy of all of the particles added together.
Internal energy can be changed in two ways:
- An change in temperature will cause an change in kinetic energy.
- A change in phase will cause an change in potential energy.

The total kinetic energy of particles can be calculated if we know the amount of moles.

If we heat up a gas in a container:
- The particles will gain kinetic energy and move faster.
- They will collide with the sides of the container more often, resulting in increased pressure.
- This could cause the container to expand or break.

The specific latent heat of a substance is defined as:
- The amount of heat energy needed to change the state of one kilogram of a substance without changing its temperature.

Keep in mind that Q is often used instead of E to represent thermal energy.
This formula is applicable in situations that include:
- Freezing or solidifying
- Condensing
- Melting
- Evaporating or boiling
When calculating the specific heat latent it is often assumed that no energy is lost during transfer.

Heating and Cooling

When heating up, for example, liquid in a beaker heated with a Bunsen burner, the liquid gains internal energy and gets hotter.
The three things that the increase in temperature depends on are:
- The amount of liquid
  - The mass of the liquid
- The amount of heat energy going in to the liquid
  - How hot the Bunsen burner is and how long it is on for
- The substance being heated
  - Some substances are easier to heat than others.
We can see that the rise in temperature depends on the mass, the amount of energy given, and the nature of the substance heated.
These three factors can be put into an equation:

This equation is rearranged from:
- ΔT = Q/mc
  - Thermal energy is proportional to increasing temperature.
  - Mass and specific heat capacity are inversely proportional as materials with greater mass and higher specific heat capacity are harder to heat up.

Specific heat capacity can be thought of as the ability of an object to store heat energy.
It's proper definition is:
- The amount of energy needed to raise the temperature of 1kg of a substance by 1°C.
- It is measured in joules per kilogram Celsius.

In an insulated situation, where no heat escapes into the surroundings:
- Thermal energy lost is always equal to thermal energy gained.

This law is used when solving calorimetry problems for finding the final temperature of a system.
- For example, consider a hot metal sword dipped into water.
- The thermal energy lost by the sword as it cools is equal to the thermal energy gained by the water as it heats up.
- However, water has a very high specific heat capacity, so it wont increase in temperature as much as the sword loses temperature, despite gaining the same thermal energy.
- For these kinds of questions you need to assume that no energy is lost to or gained from the surroundings.

Sources

https://www.youtube.com/watch?v=pQMHV8u2CLQ