Thermal Energy and Radioactivity Lecture Flashcards

Vocabulary-focused flashcards covering thermodynamics, temperature scales, heat transfer methods, states of matter, and the fundamentals of radioactive decay and atomic structure.

Temperature

The average kinetic energy of molecules, or how fast they are moving.

Absolute zero

Reached at $0\,K$, the theoretical point where molecules stop moving and an object would disappear.

Fahrenheit Boiling Point of Water

$$212^\circ F$$

Fahrenheit Freezing Point of Water

$$32^{\circ}F$$

Fahrenheit Freezing Point of Salt Water

$$32^\circ F$$

Kelvin Boiling Point of Water

$$273\,K$$

Kelvin Freezing Point of Water

$$273\,K$$

Celsius Boiling Point of Water

$$100^\circ C$$

Celsius Freezing Point of Water

$$0^\circ C$$

Thermal Energy

The total amount of energy in a sample of a substance.

Heat

A transfer of thermal energy.

Thermal Equilibrium

When all particles reach the same temperature and stop exchanging heat.

Newton's Law of Cooling

The rate of cooling depends on the temperature difference.

Conduction

Transfer of energy through a solid or between two substances in physical contact.

Convection

Transfer of energy through a fluid due to density differences caused by temperature changes.

Radiation

Transfer of energy through a vacuum via electromagnetic waves; all matter emits radiation.

Insulators

Materials that prevent heat transfer, often containing spaces like a vacuum or mirrors in a thermos.

Plasma

A gas made of positive ions and electrons at a high temperature, found in the Northern lights and fluorescent lights.

Sublimation

A phase change where a substance goes directly from a solid to a gas.

Condensation

A phase change where a substance goes from gas to liquid.

Endothermic

A process where heat is pulled in, such as an ice pack.

Exothermic

A process where heat is pushed out, such as a hand warmer.

Specific Heat Capacity

The amount of heat energy required to raise the temperature of one gram of a substance by $1^\circ C$.

Calorie (Energy Unit)

A unit of measurement for energy where $1000\,c = 1\,kcal = 1\,C$ (food calorie).

First Law of Thermodynamics

Relates to the gain or loss of thermal energy in or out of a system.

Second Law of Thermodynamics

Heat moves spontaneously from a high temperature to a low temperature.

Third Law of Thermodynamics

No system can reach absolute zero.

Strong Nuclear Force

The force that holds protons and neutrons together in the nucleus at short distances.

Alpha Particle ($\alpha$)

A positively charged subatomic particle ($He$ nucleus) consisting of 2 protons and 2 neutrons; stopped by paper.

Beta Particle ($\beta$)

A high-speed electron ($e^-$) emitted by radioactive decay; stopped by metal.

Gamma Radiation ($\gamma$)

A high energy electromagnetic wave that goes through paper and metal but is stopped by lead.

Photoelectric Effect

The ejection of electrons from a material.

Isotope

Atoms with the same number of protons but a different number of neutrons, such as $U-235$ and $U-238$.

Ion

An atom that has lost or gained electrons.

Radioactive Transmutation

When an atom becomes a different element because the number of protons changes in the nucleus during decay.