Energy Forms, States of Matter, and Thermal Physics

Vocabulary flashcards reviewing key definitions, forms of energy, particle states of matter, thermal physics concepts, and core physics calculation formulas.

Law of conservation of energy

States that energy can neither be created or destroyed, only transformed from one form to another or transferred from one object to another.

Energy (definition and units)

The ability to do work; measured in Joules ($\text{J}$).

Kinetic energy

Energy an object has when it is moving (e.g., moving car, rolling ball, a person running). It depends on the mass of the object and the square of its speed.

Gravitational potential energy

Energy stored in an object due to it being a height (in $\text{m}$) above ground (e.g., a book on a shelf, a roller coaster at the top of the ride).

Elastic potential energy

Energy stored in an object due to it being stretched or compressed (e.g., a stretched rubber band, a compressed spring in a toy, a drawn back bow).

Thermal energy

Energy stored in an object due to the number of particles in the object and their temperature (e.g., body heat, a hot cup of coffee, the Sun warming your skin).

Heat

Energy that is caused by the transfer of thermal energy. Transfer occurs by conduction, convection, and radiation.

Electrical energy

Energy of moving electric charges (electrons) (e.g., battery powering a phone, lightening, electrons flowing through household wires).

Electrical potential energy

Stored electrical energy (electrons = charge) (e.g., a charged battery not in use, static electricity before it discharges).

Sound energy (as waste form)

Energy from vibrations in air or other mediums (water) (e.g., noise produced by a car engine or an airplane, air conditioning or fridge humming).

Light energy

Visible energy that travels in waves (e.g., sunlight, a torch beam).

Chemical (potential) energy

Energy stored in the chemical bonds of substances (e.g., food being metabolised by the body, fuel being burned in a car, a battery powering a torch).

Efficiency

A measure of how good something is at using energy WITHOUT wasting it; how much useful energy is gained compared to how much energy was put into the system.

Efficiency equation

$$\text{Efficiency (\%)} = \frac{\text{useful energy output}}{\text{energy input}} \times 100$$

States of matter - solid

A state where particles are tightly packed in a fixed position, movement is vibrate only, and both shape and volume are fixed.

States of matter - liquid

A state where particles are close together with no fixed position, movement allows particles to move around each other, and volume is fixed while taking the shape of the container.

States of matter - gas

A state where particles are far apart, move freely in all directions, and fill the entire container, changing both volume and shape.

Ice (particle model)

The solid phase of water, characterized by water molecules tightly packed in a fixed, structured arrangement.

Water (particle model)

The liquid phase of water, characterized by molecules that are close together with no fixed position and free to move around each other.

Water vapour (particle model)

The gas phase of water, characterized by molecules that are far apart and move freely in all directions.

Latent heat of fusion

The amount of energy to weaken ($\text{S} \rightarrow \text{L}$, melting) or strengthen bonds ($\text{L} \rightarrow \text{S}$, freezing) without a change in temperature.

Latent heat of vaporisation

The amount of energy to change the state ($\text{L} \rightarrow \text{G}$) without a change in temperature; occurs at the boiling point of the substance.

Specific heat capacity

The amount of heat energy needed to change the temperature of $1\,\text{kg}$ of the substance by $1^\circ\text{C}$. The higher the SHC, the more energy is needed to change the temperature of the substance.

Heating curve (for water)

A plot of temperature ($^\circ\text{C}$) versus time illustrating solid heating, $\text{S to L}$ phase change at $0^\circ\text{C}$, liquid heating, $\text{L to G}$ phase change at $100^\circ\text{C}$, and gas heating.

$$\Delta E = Pt$$

Equation for energy transferred by power: $\Delta E = \text{energy transferred (J)}$, $P = \text{power (W, which is joules per second)}$, and $t = \text{time (s)}$.

$$E_k = \frac{1}{2}mv^2$$

Equation for kinetic energy: $E_k = \text{kinetic energy (J)}$, $m = \text{mass of the object (kg)}$, and $v = \text{speed (m}\,\text{s}^{-1}\text{)}$.

$$E_p = mg\Delta h$$

Equation for gravitational potential energy: $E_p = \text{gravitational potential energy (J)}$, $m = \text{mass (kg)}$, $g = \text{gravitational field strength (on Earth, } 10\,\text{N/kg)}$, and $\Delta h = \text{change in height (m)}$.

$$W = Fd$$

Equation for work done: $W = \text{work done (J)}$, $F = \text{force applied (N)}$, and $d = \text{distance moved in the direction of the force (m)}$.

$$E(\text{thermal}) = mc\Delta T$$

Equation for thermal energy during a temperature change: $E(\text{thermal}) = \text{energy gained or lost (J)}$, $m = \text{mass of the substance (kg)}$, $c = \text{specific heat capacity (J/(kg}\cdot^\circ\text{C))}$, and $\Delta T = \text{change in temperature (}^\circ\text{C)}$.

$$E(\text{thermal}) = mL$$

Equation for thermal energy during a phase change: $E(\text{thermal}) = \text{energy transferred (J)}$, $m = \text{mass of the substance (kg)}$, and $L = \text{latent heat (J/kg)}$ (such as $L_f$ for fusion).