Packet #3: Energy and Phase Changes

Vocabulary practice flashcards covering fundamental chemistry concepts including forms of energy, conservation laws, temperature scales, states of matter, phase changes, heating and cooling curves, and thermochemical calculations.

Energy

The ability to do work or the ability to change motion, which exists in many different forms and can be changed from one form to another.

Law of Conservation of Energy

A physical law stating that energy cannot be created nor destroyed, only changed from one form to another.

Chemical Energy

Energy absorbed or released during a chemical reaction.

Electrical Energy

Energy produced by the flow of electrons.

Electromagnetic Radiation

Energy that travels in waves.

Heat (Thermal) Energy

Energy arising from the random movement of atoms and molecules.

Mechanical Energy

Energy possessed by moving objects.

Nuclear Energy

Energy given off when an atomic nucleus breaks up into smaller nuclei or when smaller nuclei join to form a larger nucleus.

Kinetic Energy

The energy of motion.

Potential Energy

Stored energy, also described as energy of position.

Chemical Reaction

A well-defined chemical change in which atoms rearrange to form new substances with different properties than the original substances.

Reactants

The starting material in a chemical reaction.

Product

A new substance formed as the result of a chemical reaction.

Law of Conservation of Mass

A fundamental law stating that matter cannot be created or destroyed during a chemical change, meaning the total mass of the reactants must equal the total mass of the products.

Endothermic

A process where energy is absorbed, products contain more internal energy than reactants, energy is written on the left side of the equation, and the surrounding temperature decreases.

Exothermic

A process where energy is released, reactants contain more internal energy than products, energy is written on the right side of the equation, and the surrounding temperature increases.

Temperature

A measure of the average kinetic energy of particles that does not depend on the amount of matter present.

Absolute Zero

The lowest theoretical temperature that can be reached ($0\,\text{K}$ or $-273\,^\circ\text{C}$), defined as the temperature at which no heat can be transferred out of matter.

Solid

A phase of matter having a definite shape and volume, consisting of particles packed closely together in a rigid, crystalline geometric pattern that vibrate without translating.

Liquid

A phase of matter with a definite volume but no definite shape, containing particles that remain close together and touch while moving past one another without a regular pattern.

Gas

A phase of matter with no definite shape and no definite volume, whose particles are very far apart and expand in all directions to fill the container.

Phase Change

The conversion of a substance from one physical state of matter to another, always accompanied by an absorption or release of energy.

Sublimation

The phase change in which a solid changes directly into a gas without passing through the liquid phase (such as with solid $CO_2$ or solid $I_2$).

Deposition

The phase change in which a gas transforms directly into a solid without an intermediate liquid phase.

Heating Curve

A graph showing temperature versus time as heat is added at a constant rate starting below a substance's melting point to above its boiling point; all phase changes on it are endothermic.

Cooling Curve

A graph representing the condensation of a gas to a liquid and solidification of a liquid to a solid; all phase changes on it are exothermic.

Specific Heat Capacity ($C$)

The amount of heat needed to raise the temperature of $1\,\text{gram}$ of water by $1\,^\circ\text{C}$, equal to $4.18\,\text{joules}/(\text{g}\cdot^\circ\text{C})$ for water.

Heat of Fusion ($H_f$)

The amount of heat absorbed by a solid to become a liquid, or released by a liquid to become a solid, at constant temperature ($334\,\text{joules/gram}$ for water).

Heat of Vaporization ($H_v$)

The amount of heat absorbed by a liquid to become a gas, or released by a gas to become a liquid, at constant temperature ($2260\,\text{joules/gram}$ for water).