Glossary
Avogadro's Law
A gas law stating that for a fixed temperature and pressure, the volume of a gas is directly proportional to the number of moles of gas. More gas means more volume.
Example:
When you inflate a party balloon, you are adding more air molecules, and Avogro's Law explains why the balloon's volume increases.
Boltzmann Constant (k_B)
A physical constant relating the average kinetic energy of particles in a gas to the absolute temperature of the gas. It is used in the alternative form of the Ideal Gas Law (PV = Nk_BT).
Example:
The Boltzmann Constant helps us understand the microscopic connection between the random motion of individual atoms and the macroscopic temperature we measure.
Boyle’s Law
A gas law stating that for a fixed amount of gas at constant temperature, the pressure and volume are inversely proportional. As volume increases, pressure decreases.
Example:
When you push down on the plunger of a syringe with the end blocked, the volume of the air decreases, and Boyle's Law dictates that its pressure will increase.
Charles' Law
A gas law stating that for a fixed amount of gas at constant pressure, the volume is directly proportional to its absolute temperature. As temperature increases, volume increases.
Example:
A balloon left in a warm car will expand due to Charles' Law, as the air inside heats up and increases in volume.
Gay-Lussac’s Law
A gas law stating that for a fixed amount of gas at constant volume, the pressure is directly proportional to its absolute temperature. As temperature increases, pressure increases.
Example:
Heating a sealed aerosol can can be dangerous because, according to Gay-Lussac's Law, the increasing temperature will cause the internal pressure to rise significantly.
Heat
The transfer of thermal energy between objects or systems due to a temperature difference. It always flows from a region of higher temperature to one of lower temperature.
Example:
When you touch a hot stove, heat transfers from the stove to your hand, causing a burning sensation.
Ideal Gas
A theoretical gas composed of many randomly moving point particles that do not interact with each other except through perfectly elastic collisions. It serves as a useful approximation for real gases under certain conditions.
Example:
While no gas is perfectly ideal, helium at room temperature and atmospheric pressure behaves very much like an ideal gas.
Ideal Gas Constant (R)
A universal physical constant that appears in the Ideal Gas Law (PV = nRT), relating the energy scale to the temperature scale when dealing with moles of gas. Its value depends on the units used for pressure, volume, and temperature.
Example:
When calculating the volume of a gas at standard temperature and pressure, you would use the appropriate value for the Ideal Gas Constant in the Ideal Gas Law equation.
Ideal Gas Law
A fundamental equation that describes the relationship between pressure, volume, temperature, and the number of moles of an ideal gas. It is expressed as PV = nRT.
Example:
Engineers use the Ideal Gas Law to predict how the pressure inside a car engine's cylinders will change as the fuel-air mixture is compressed and heated.
Kinetic Energy
Energy possessed by an object due to its motion. For gas molecules, it's the energy associated with their translational, rotational, and vibrational movements.
Example:
A baseball thrown by a pitcher possesses significant kinetic energy due to its speed and mass.
Pressure (P)
Force applied perpendicularly to a surface per unit area. In gases, it arises from the constant collisions of gas molecules with container walls.
Example:
When you inflate a bicycle tire, the air molecules inside push against the inner tube, creating the pressure that keeps the tire firm.
Root Mean Square (RMS) Speed
A statistical measure of the average speed of molecules in a gas, calculated as the square root of the average of the squares of their speeds. It provides a representative speed for the ensemble of molecules.
Example:
Even though individual gas molecules move at varying speeds, the Root Mean Square (RMS) Speed gives us a single value to describe their typical velocity at a given temperature.
Temperature
A measure of the average kinetic energy of the particles within a substance. It indicates the degree of hotness or coldness of an object.
Example:
The temperature of a room tells us how fast, on average, the air molecules are moving.
Thermal Energy
The total kinetic energy of the atoms and molecules within a substance, associated with its temperature. It represents the internal energy due to the random motion of particles.
Example:
A hot cup of coffee has more thermal energy than a cold one because its water molecules are moving and vibrating more rapidly.
Thermal Equilibrium
A state where two or more objects in contact have reached the same temperature, resulting in no net transfer of heat between them. Microscopic collisions still occur, but there's no overall energy flow.
Example:
If you leave a cold drink on a table, it will eventually reach thermal equilibrium with the room, meaning its temperature will match the room's temperature.