# Physics - Thermal Physics

## See Also

- [[Physics - Ideal Gases]]
^{A} - [[Physics - Recall for Chapter 15; Ideal Gases]]
^{A} - [[Physics - Recall for Chapter 14; Thermal Physics]]
^{A}

## Flashcards

What two points define the Kelvin scale?

- Absolute zero
- Triple point of water

What is the triple point of water?

The point at which water is a solid, liquid and gas simultaneously.

How can you have a solid, liquid and a gas simultaneously?

By setting an exact pressure and temperature.

What is $0K$ in Celsius?

What is $0^\circ$ in Kelvin?

What is the equation for converting Kelvin $T$ to Celsius $\theta$?

What is the equation for converting Celsius $\theta$ to Kelvin $T$?

What does it mean for two objects to be in thermal equilibrium?

There is no net transfer of thermal energy between them.

### 2021-09-10

What is the kinetic model?

The explanation of solids, liquids and gasses as substances made up of atoms.

What is the order of solids, liquids and gasses for increasing potential energy?

- Solid
- Liquid
- Gas

What is the maximum potential energy in a gas?

What force holds molecules together in solids and liquids?

The electrostatic force.

What causes Brownian motion in things like smoke or pollen particles?

Collisions with smaller, hard to see particles.

### 2021-09-13

Why does heating an object at a state change not increase its temperature?

All energy is going towards potential energy rather than kinetic energy.

What is the $\text{internal energy}$ equation?

What is the wordy definition of internal energy?

The sum of the randomly distributed kinetic and potential energies of atoms or molecules in a substance.

Energy supplied to an object is increasing the kinetic energy. What happens as a consequence?

The temperature increases.

Energy supplied to an object is increasing the potential energy. What happens as a consequence?

The object is changing state.

Why is the potential energy the highest at $0J$ in a gas?

Because no work is needed to pull the particles apart.

Why is the potential energy the most negative in a solid?

Because you need to do a lot of work to pull the particles apart.

### 2021-09-18

What is the specific heat capacity of a substance?

The energy required to raise a $1kg$ mass by $1K$.

What is the equation for the specific heat capacity of a substance $c$?

What is the equation for the energy $E$ required to heat by $\Delta\theta$?

What are the units for specific heat capacity?

What’s the equation for the specific heat capacity of a material after supplying $V$ volts at $I$ amps for $t$ seconds to a mass $m$ and finding a temperature difference $\theta _ 2 - \theta _ 1$?

### 2021-10-12

What is the method of mixtures?

A technique for determining the specific heat capacity of a material by measuring the final equilibrium temperature when added to another substance.

What principle allows you to use the method of mixtures?

(at thermal equilibrium)

What is true about the final equilibrium temperature of two different objects?

It is equal.

### 2021-10-14

What is the equation for the energy of a state transition (specific latent heat)?

What are the units for $L$, the specific latent heat?

What is $L _ f$ in relation to specific latent heat?

The specific latent heat of fusion.

What is $L _ v$ in relation to specific latent heat?

The specific latent heat of vaporization.

What is the specific latent heat of fusion?

The energy gained or lost at the solid/liquid state transition.

What is the specific latent heat of vaporization?

The energy gained or lost at the liquid/gas state transition.

How would you calculate the energy required to heat water to $120^{\circ}$ from $20^{\circ}$?

What is the specific latent heat of fusion for water?

What is the specific latent heat of vaporization for water?

What’s normally bigger: the specific latent heat of fusion or the specific latent heat of vaporization?

The specific latent heat of vaporization.

### 2022-01-08

What is Boyle’s law?

What is Charles’s law?

What is the pressure law/Gay-Lussac’s law?

What is an isochoric change in a gas?

Where the volume of the gas remains constant.

### 2022-01-20

What is true about the mean kinetic energy of particles for two objects in thermal equilibrium (e.g. a metal container of water)?

It is equal.

How should you describe the movement of particles in a solid?

Vibrating about a fixed point.

How should you describe the movement of particles in a liquid?

Moving freely past each other (not just moving freely) randomly.

How should you describe the movement of particles in a gas?

Moving freely.

### 2022-03-02

What must you specify about an electric heater in a question about specific heat capacity?

That it is fully immersed in the medium.

### 2022-03-07

How can you justify that the potential energy of a gas is larger than that of a liquid?

Energy must be supplied to a liquid to change its state.

### 2022-03-08

What’s better than saying “heat is lost to the surroundings”?

Heat is lost to *something specific*.

When describing how pressure comes about using particle collisions with container walls, what must you add after showing particles exert a force on the container walls?

That pressure is the sum of these forces over the area.

What is one potential reason all the energy from a laser might not be transmitted to a metal?

Reflection on the surface of the metal.

### 2022-04-14

Given the molar masses of two gases, and the mean speed of one of the gases at a certain temperature, how could you work out the mean speed of the other gas at the same temperature?

Use the fact that $\frac{1}{2} mv^2$ must be equal for both.

How does Brownian motion provide evidence for gas molecules continuously moving?

The larger particles are continuously moving.

How does Brownian motion provide evidence for a large number of gas molecules?

The overall movement is small due to molecules hitting from all sides.

### 2022-05-03

When describing the practical for determining the specific heat capacity of a liquid, what must you connect across the heater?

A voltmeter.

### 2022-05-04

“The molecules are in a tight, fixed lattice due to the electrostatic forces…” No. What should it be instead?

“strong electrostatic forces”

Why is there still a transfer of thermal energy between two objects at equilibrium?

Energy is always being transferred but it’s only when there is a temperature difference that there is a *net* transfer.

“In a liquid, molecules are no longer tightly bound…” No. What should it be instead?

Closely packed due to fairly strong electrostatic forces.

What can you match up in terms of kinetic energy, potential energy, molecule speed and molecule separation in a substance?

- Kinetic energy increases with molecule speed
- Potential energy increases with molecule separation

“Specific latent heat of fusion is the energy required to change the temperature of a substance from solid to liquid per unit mass…” No. What is an important clarification when defining latent heat?

“Without changing its temperature”