Question
Please explain...
- A description of the expansion of solids,liquids and gases
- A comparison of adiabatic and isothermal expansion
- A discussion of changes of state
Explanation / Answer
a)Solid Expansion upon heating - Brass ball and hoop experiment. My chemistry teacher did an experiment where he put a brass ball through a hoop designed so it could only just fit through it. He then heated the brass ball under a bunsen flame and tried to put it through... the brass ball had expanded due to an increase the energy level of the atoms. Expansion of gas - Gas likes to fill the space of the room it's in. Heating the gas in a balloon tends to make the particles gain energy. They move faster hitting the sides of the container and appearing to expand ----> Air Balloon (although note it rises for a slightly different reason). Expansion of liquid - A difficult one. I've looked up on a resource and tried to coin it down for you. Under pressure, heating a liquid (in a sealed container) will cause it to expand. Better though, I would go with the ice explained below. b)Let us suppose that for an ideal gas, isothermal and adiabatic expansions have initial volume Vi and pressure be Pi to a common final volume Vf. If Piso and Padia are the final pressures, then: For isothermal expansion Pi Vi = Piso Vf And for adiabatic expansion, Pi V? i = Padia (Vf) ? Therefore, Vf/Vi = Pi/Piso And Vf/Vi = Pi/Padia As for expansion (Vf) > (Vi) and also for all gases ? > 1 , hence {(Vf/ Vi) ?} > {Vf/ Vi} Therefore {Pi/ Padia} > {Pi/ Piso} Or (Padia) < (Piso) c)Physical Changes Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.