chap 2 kinetic particle theory

what is the kinetic particle theory?

it states that all matter is made uo of tiny particles, which move randomly all the time.

solid ( arrangement, forces of attraction, motion, kinetic energy )

arrangement : very closely packed and arranged in an orderly manner

forces : very strong

motion : vibrate or rotate about fixed positions

kinetic energy of particles : very low

liquid ( arrangement, forces of attraction, motion, kinetic energy )

arrangement : closely packed but arranged in a disoderly manner

forces : less strong than forces of attraction between solid

motion : moves freely throughout the liquid

kinetic energy : low but higher than the kinetic energy of the particles in a solid

gas ( arrangement, forces of attraction, motion, kinetic energy )

arrangement : very far apart and arranged in a disorderly manner

forces : very weak

motion : move rapidly and freely in any direction

kinetic energy : high

what happens when particles in a solid gain heat

kinetic energy of the particles in the solid increases. the particles vibrate more quickly about their fixed positions.

what happens when a solid melts

• forces of attraction between the particles in the solid are overcome by the motion of the particles

• melting occurs. the substance changes from a solid to a liquid

• temperature remains constant as melting occurs

how is KE affected by heat gain / heat loss?

heat gain → KE increase

heat loss → KE decrease

when a gas cools

temperature of the gaseuous substance decreases until it reaches its condensation point. some kinetic energy of the particles in the gas is transferred to the surroundings as heat. the particles move more slowly.

when a gas starts to condense

forcces of attraction between the particles in the gas increase. condensation occurs. the substance changes from a gas to a liquid. temperature remains constant as condensation occurs.

pure substance boiling and condensation point relationship.

as a pure ubstances boils and codenses at the same temp, the boiling point of a substance is also its condensation point

boiling

• occurs at the boiling point of a substance only

• it occurs throughout a substance in the liquid state

• the temperature of the substance remains constant untl all f the substance has changed to the gaseous state

evaporation

• occurs at temperatures below the boiling point of the substance

• it occurs only at the surface of a substance in the liquid state

• the temperature of the substance decreases

what are liquids that evaporate quickly called?

volatile liquids

eg ethanol (78C), propanone ( 56C)

sublimation

the process in which a substance in the solid state changes into the gaseous state directly without going through the liquid state.

vapour deposition

the reverse of sublimation

the process in which a substance in the gaseous state changes into the solid state directly without going through the liquid state

example of substances that undergo sublimation

iodine, dry ice

wheb does change in state from solid to gaseous take place

when particles at the surface of the solid possess sufficient energy to break away from the solid and escape as a gas