latent heat of vaporisation - the amount of energy needed to evaporate or condense the material at its boiling point.
Calculating thermal energy changes
- change in thermal energy (ΔE t) is measured in joules (J)
- mass (m) is measured in kilograms (kg)
- specific latent heat (l) is measured in joules per kilogram (J/kg)
Latent and sensible heat are types of energy released or absorbed in the atmosphere. Latent heat is related to changes in phase between liquids, gases, and solids. Sensible heat is related to changes in temperature of a gas or object with no change in phase.
Latent heat is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process. Two common forms of latent heat are latent heat of fusion (melting) and latent heat of vaporization (boiling).
The latent heat of fusion is the heat required for an object to go from the solid state to the liquid state, or vice versa. Since its value is generally much higher than specific heat, it allows you to keep a beverage cold for much longer by adding ice than simply having a cold liquid to begin with.
A total of 334 J of energy are required to melt 1 g of ice at 0°C, which is called the latent heat of melting. At 0°C, liquid water has 334 J g−1 more energy than ice at the same temperature. This energy is released when the liquid water subsequently freezes, and it is called the latent heat of fusion.
Here is the formula: Eh = m x l. Eh means energy, equals m for mass, times l. l is the specific latent heat of fusion for that material. So the formula tells us how much heat energy is needed to go into a material to change it from a solid to a melted liquid.
Overview. The 'enthalpy' of fusion is a latent heat, because during melting the heat energy needed to change the substance from solid to liquid at atmospheric pressure is latent heat of fusion, as the temperature remains constant during the process. The liquid phase has a higher internal energy than the solid phase.
As the latent heat of steam at atmospheric pressure is 2257 kJ/kg the amount of flash steam produced will be 299/2257 = 0.133 kg/kg of condensate. Flash steam can be piped to an evaporator, calorifier or vat or can be used for heating in a contact heater.
Latent heat is sometimes called the 'hidden' or 'stored' heat used to change the state of a substance without a change in temperature. The temperature does not increase as the water (liquid) starts to evaporate and become water vapour (a gas).
Or, L = [M1 L2 T-2] × [M1 L0 T0]-1 = [M0 L2 T-2]. Therefore, latent heat is dimensionally represented as [M0 L2 T-2].
Both latent and sensible heat fluxes are negative because the ground is cooling and water vapor is condensing, leading to a positive gradient in temperature and specific humidity.
Note that latent heat is related with no adjustment in temperature, yet a difference in the state.
Answer: Latent heat is defined as the heat or energy that is absorbed or released during a phase change of a substance. It could either be from a gas to a liquid or liquid to solid and vice versa. Latent heat is related to a heat property called enthalpy.
The term sublimation is the passage or the transformation or conversion that substances undergo when passing from one state to another, for example from a solid substance to gas. We can define sublimation as the transition of a substance from the solid phase to the gaseous phase without changing into the liquid phase.
Latent heat of condensation is energy released when water vapor condenses to form liquid droplets. The latent heat of condensation is defined as the heat released when one mole of the substance condenses. The energy released in this process is called heat of condensation.
When a substance changes phase, the arrangement of its molecules changes, but its temperature does not change. Latent heat of vaporization is a physical property of a substance. It is defined as the heat required to change one mole of liquid at its boiling point under standard atmospheric pressure.
The process of liquid changing into vapours even below its boiling point is called as evaporation. Thus,the fast moving particles of a liquid are constantly escaping from the liquid to form vapour. Factors affecting evaporation. 1)Temperature. The rate of evaporation increases on increasing temperature of the liquid.
