energy and kinetic theory

energy

the capacity to do work

when is work done

when motion occurs against a force

a conservative system

no energy is lost

particle volume

Gas molecules have negligible size compared with the volume of the container - they are treated as point masses. Particle separation is much greater than the size of the particles themselves

particle motion

The molecules do not interact with each other. Epe = 0

particle collisions

Collisions are elastic, molecules exchange energy but do not lose energy. The total kinetic energy (KE) is constant

basis of collisions

a gas consists of molecules that are in constant random motion in all directions throughout the container

atomic gases only have

translational kinetic energy

molecular gases

also have kinetic energy

distribution of molecular speed

at a given temperature some molecules move at high speed and some at low speeds. Most of the molecules move at an intermediate speed

Boltzmann constant

conveys the energy per unit temperature for an individual molecule. K_BT is the average kinetic energy of a molecule at a particular temperature

what causes gas pressure

molecules bombarding the container walls

origin of pressure

• Due to molecules colliding with the walls

• Number of molecules hit the container wall per second - concentration

• Force exerted by the molecules when they hit it

• Speed of the molecules - temperature

effusion

at a given temperature and gas pressure, the rate of effusion (that is, the number of molecules passing through the hole per second) is inversely proportional t the square root of the molar mass, M.

ideal gas

molecules have no size and there are no intermolecular forces

real gas

molecules have size, which reduces volume available to move in. Molecules have intermolecular attraction, which reduces the force with which they hit walls