Properties of gases

Week 1-2

Avogadro's number

Number of atoms, molecules, or ions in one mole of a substance, which is approximately 6.022 x 10^23 mol-1.

Extensive properties (example)

Depends on the size or amount of matter in a system. E.g. mass and volume

Intensive properties (example)

Independent from the size or amount of matter in a system. E.g. pressure, temperature

The physical state is defined by …

its physical properties

Mechanical equilibrium

The condition of equality of pressure on either side of a shared movable wall.

Equation of state

Equation that interrelates the variables that define the state of a substance.

Limiting law

A law that is strictly true only in a certain limit 

Boyle’s law

At a constant temperature, the **pressure** of a gas is **inversely proportional** to its **volume**.

Dalton’s law

The pressure exerted by a **mixture** of (perfect) gases is the **sum** of the pressures that each one would exert if it occupied the container alone.

The kinetic model of a gas considers only …

The contribution to the energy from the kinetic energies of the molecules.

Root-mean-square speed

The average speed of particles in a gas, calculated by taking the square root of the sum of the squares of the individual speeds, divided by the number of particles.

The collision frequency

The average number of collisions made by a molecule in an interval divided by the length of the interval.

The mean free path

The average distance a molecule travels between collisions.

Compression factor

The ratio of the volume of a gas at standard conditions to its volume under the current conditions

The virial equation

An empirical extension of the perfect gas equation that summarizes the behaviour of real gases over a range of conditions.

A gas can be liquefied by pressure alone only if its temperature is at or below its ...

Critical temperature.

The van der Waals equation

A model equation of state for a real gas expressed in terms of two parameters, one (*a*) representing molecular attractions and the other (*b*) representing molecular repulsions.

Standart Ambient Temperature and Pressure

298\.15K and 1 bar

The van der Waals equation captures the general features of …

the behaviour of real gases, including their critical behaviour.

The properties of real gases are coordinated by expressing their equations of state in terms of …

reduced variables.

Avogadro’s principle

Equal volumes of gases at the same temperature and pressure contain the same number of molecules.

Charles’s law

At a constant pressure, the **volume** of a gas is **directly proportional** to its **temperature**.