Phase Changes

Tuesday, 29 May 2018

1:28 PM

• When a substance changes form
• A substance can have no change in its temperature when given heat
• The energy required to effect the change is known as the Latent Heat
• 

Q - energy to change the phase (J)
m - mass (kg)

Use  when there is no phase change

Use  when there is a phase change

Energy into a system =  

Energy out of a system =  

 

 

 

 

• A phase change requires a 'nucleation site' (a disturbance)

As a consequence, if a disturbance does not occur, a substance (ie water) can stay in its current phase - ie supercooling and superheating

(Ie you can have water in its liquid state below  that will only turn into ice if you quickly thump it)