3.6.2. Thermal physics
Thermal energy transfer
Internal energy def.?
- sum of the randomly distributed kinetic energies and potential energies of the particles in a
body
Ways to inc. the internal energy of a system?
1) transfer energy to it by heating
2) work is done on it
First law of thermodynamics?
- energy cannot be created or destroyed, only transferred from one store/form to another
Change of temp. equation?
-
- Q = heat energy
- c = specific heat capacity
What does a high specific heat capacity mean?
- substance heats up and cools down slowly
← bcs it takes much more heat energy to change its temp.
What does a low specific heat capacity mean?
- substance heats up and cools down quickly
← bcs it takes much less heat energy to change its temp.
Energy changes during heating/cooling a substance?
- KE changes (as the temp. is the average KE of a system)
- potential energy stays the same
⇒ since KE changes, internal energy changes
Change of state equation?
-
- Q = heat energy
- l = specific latent heat
Specific latent heat def.?
AND
MUST SAY: “with no change in temp.”
Diff. between latent heat of vaporisation and fusion?
- vaporisation - boiling, condensing ← between liquid and gas state
- fusion - melting, freezing ← between solid and liquid state
Energy changes during changing the state of a substance?
- KE stays the same
- potential energy changes
⇒ since potential energy changes, internal energy changes
Why do we have a specific latent heat of fusion and then a separate for evaporation
for a substance e.g. water?
- the specific latent heat of fusion (transitioning between solid and liquid) has a WAY lower
,value than the specific latent heat of evaporation (transitioning between liquid and gas)
→ bcs:
, Sublimation def.?
- solids vaporise to gas
- when heated
Practical: Find specific heat capacity of a material using an inversion tube
Thermal energy transfer
Internal energy def.?
- sum of the randomly distributed kinetic energies and potential energies of the particles in a
body
Ways to inc. the internal energy of a system?
1) transfer energy to it by heating
2) work is done on it
First law of thermodynamics?
- energy cannot be created or destroyed, only transferred from one store/form to another
Change of temp. equation?
-
- Q = heat energy
- c = specific heat capacity
What does a high specific heat capacity mean?
- substance heats up and cools down slowly
← bcs it takes much more heat energy to change its temp.
What does a low specific heat capacity mean?
- substance heats up and cools down quickly
← bcs it takes much less heat energy to change its temp.
Energy changes during heating/cooling a substance?
- KE changes (as the temp. is the average KE of a system)
- potential energy stays the same
⇒ since KE changes, internal energy changes
Change of state equation?
-
- Q = heat energy
- l = specific latent heat
Specific latent heat def.?
AND
MUST SAY: “with no change in temp.”
Diff. between latent heat of vaporisation and fusion?
- vaporisation - boiling, condensing ← between liquid and gas state
- fusion - melting, freezing ← between solid and liquid state
Energy changes during changing the state of a substance?
- KE stays the same
- potential energy changes
⇒ since potential energy changes, internal energy changes
Why do we have a specific latent heat of fusion and then a separate for evaporation
for a substance e.g. water?
- the specific latent heat of fusion (transitioning between solid and liquid) has a WAY lower
,value than the specific latent heat of evaporation (transitioning between liquid and gas)
→ bcs:
, Sublimation def.?
- solids vaporise to gas
- when heated
Practical: Find specific heat capacity of a material using an inversion tube
