Latent Heat Flashcards
1
Q
Latent Heat
A
the energy released or absorbed during a change of state
2
Q
Latent heat of fusion
A
the amount of energy needed to melt a solid is the same amount of potential energy released when the liquid re-forms into a solid.
- As thermal energy is transferred to a solid, the temperature of the solid increases.
- The particles within the solid gain internal energy (as kinetic energy and some potential energy) and their speed of vibration increases.
- At the point where the solid begins to melt, the particles move further apart, reducing the strength of the bonds holding them in place.
- At this point, instead of increasing the temperature, the extra energy increases the potential energy of the particles, reducing the interparticle or intermolecular forces.
- No change in temperature occurs as all the extra energy supplied is used in reducing these forces between particles.
3
Q
Latent heat of vaporisation
A
the amount of energy required to change a liquid to a gas is exactly the same as the potential energy released when the gas returns to a liquid.
- It takes much more energy to convert a liquid to a gas than it does to convert a solid to a liquid.
- This is because, to convert a liquid to a gas, the intermolecular bonds must be broken.
- During the change of state, the energy supplied is used solely in overcoming intermolecular bonds.
- The temperature will not rise until all the material in the liquid state is converted to a gas, assuming that the liquid is evenly heated.
4
Q
Rate of vaporisation of a liquids depends on:
A
- the volatility of the liquid: more volatile liquids evaporate faster, tendency of a substance toevaporate at normal temperatures.
- the surface area: greater evaporation occurs when greater surface areas are exposed to the air
- the temperature: hotter liquids evaporate faster
- the humidity: less evaporation occurs in more humid conditions
- air movement: if a breeze is blowing over the liquid’s surface, evaporation is more rapid
