chem modelsofparticulatenatureofmatter
Structure 1.5.1 - an ideal gas consists of moving particles with negligible volume and no intermolecular forces. all collisions between particles are considered elastic.
the theoretical model of an ideal gas is assumed to obey the following axioms:
- the particles in a gas have negligible volume compared with the volume the gas occupies - thus, the chemical nature of the gas makes no difference
- there are no intermolecular forces between the particles except when the molecules collide
- gas particles have a range of speeds and move randomly. the average kinetic energy of the particles is proportional to the temperature
- the collisions of the particles with the walls of the container and with each other are elastic: kinetic energy is conserved
the pressure of a gas is due to gas particles colliding with the walls of the container. it is the same on all walls.
when the volume of a gas increases, the gas particles collide less frequently with the walls since they travel greater distances between collisions. this decreases the pressure. the model correctly predicts that increasing the volume decreases the pressure.
when the temperature of a gas increases, the gas particles have increased kinetic energy according to the third axiom. the collisions with the walls are more energetic and more frequent as the particles are moving faster. both these factors increase the pressure
challenge questions
- What would happen to the pressure of a gas if molecular collisions were not perfectly elastic?
If molecular collisions were not perfectly elastic, kinetic energy would be lost in every collision. Then, there would be less collisions between the gas particles and the walls, so the pressure would constantly decrease until 0.