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Thermal Properties (PH10) - Coggle Diagram
Thermal Properties (PH10)
Internal energy
Internal energy = Kinetic energy + Potential energy
As particles get further away,
potential energy increases, and vice versa.
Heat capacity J/°C
Energy transferred to/from internal store (J) / change in temp (°C)
C = Q / Δθ
Change in amount of internal energy per unit change in temp.
Specific heat capacity J/(kg°C)
Change in amount of internal energy per unit mass for each unit change in its temperature
Energy transferred to/from internal store (J) / [mass (kg) x change in temp (°C)]
c = Q / mΔθ
Kelvin = °C - 273.15
1K = 1°C (by interval)
Latent heat
Energy released / absorbed to change state of a substance at a constant temperature (Joules)
Specific latent heat
Fusion (between solid and liquid)
Q (Energy in) / m (Mass) = J/kg
Vaporisation (between liquid and gas)
Evaporation
Evaporation process
Overcome collision with fast moving air particles above liquid
When faster moving particles
at the surface
escape, the average kinetic energy of the
remaining liquid particles
decreases.
The temperature of the liquid decreases
Net transfer of energy from surroundings to remaining liquid (thermal equilibrium), decreasing surrounding temperature
Overcome attractive forces from the rest of the liquid particles
Evaporation Vs Boiling
Evaporation:
does NOT need heat source
takes place ONLY at surface of liquid
rate of vaporisation is SLOWER
occurs at ANY temperature
liquid temperature tends to DROP
Boiling:
NEEDS a heat source
takes place THROUGHOUT the liquid
rate of vaporisation is FASTER
occurs only at BOILING POINT of liquid
liquid temperature remains CONSTANT
Factors affecting rate of evaporation
Higher temperature = Higher rate of evaporation
Higher wind speed = Higher rate of evaporation
Higher exposed surface area = Higher rate of evaporation
Lower boiling point of liquid = Higher rate of evaporation
Lower humidity = Higher rate of evaporation
Lower pressure = Higher rate of evaporation