Phase Changes Flashcards
What is a pure substance?
A substance that has a fixed chemical composition.
Water, Carbon dixoide
Gold, silver
What is phase?
A distinct molecular arrangement that is homogenous throughout and separated from the others by easily identifiable boundary surfaces.
What is phase equilibrium?
A system which has two phases and the mass od each phases reaches an equilibrium level and stays there.
What are the 5 stats of a pure substance?
Compressed liquid Saturated liquid Saturated liquid-vapour mixture Saturated vapour Superheated vapour
What is the difference between compressed liquid and saturated liquid?
CL-not close to vaporising
SL- On a verge of vaporisation
What is a saturated liquid-vapour mixture?
The liquid is vaporising as more heat is added
What is the difference between saturated vapour and superheated vapour?
SV-At 1 atm, the temperature remains at 100°C
SHV-Temperature of the vapour increases.
What is saturation temperature?
The temperature at which a pure substance changed phases at a given pressure.
What is saturation pressure?
The pressure at which a pure substance changes phase at a given temperature.
What is latent heat?
The amount of energy absorbed or released during a phase-change process
Q=mλ
What is sensible heat?
The energy transferred in single phase resulting in temperature change.
Q=mc∆T
What is the critical point on a T-V/p-V/p-T diagram?
Temperature at which liquid and vapour have the same density, thus are indistinguishable
What is the main difference between the same of the T-V and the p-V diagram?
For T-V the constant pressure line starts at zero and goes to infinity, after leveling.
For p-V the constant temperature it goes from infinity towards zero, after leveling off.
What does the p-T diagram look like?
A sublimation line reaches a triple point
This splits into two lines:
Melting and vaporisation
The area below the triple point are solid/vapour.
Above are solid, melting, vaporisation and vapour.
