Q:

How do you explain the enthalpy of vaporization?

A:

The enthalpy of vaporization is the energy, in the form of heat, that a substance needs to change from a liquid to a gas at a constant temperature and pressure. Enthalpy of vaporization, designated as "delta H vap," is measured in kilojoules per mole of substance. The amount of heat needed to change 2.2 pounds of water into steam is 2,257 kilojoules, or 2,2257 kJ/mol.

Keep Learning

Credit: Tristan Schmurr CC-BY-2.0

Tables denote various enthalpies of vaporization that scientists use to calculate how much heat is needed to change a liquid to a gas. Oxygen has an enthalpy of vaporization of 6.82, methane's is 8.18, chlorine's is 20.41, and carbon tetrachloride's is 30.00 kJ/mol. Heavier substances require greater heat, such as aluminum at 284 kJ/mol and lead at 178 kJ/mol. When the boiling points of substances are higher, the enthalpies of vaporization are also higher.

Enthalpy denotes energy added or taken away from atoms and molecules. When matter changes states, heat is added or taken away from the chemical. Enthalpies of vaporization denote heat added to mass to change from a liquid to a gas. Conversely, the enthalpy of condensation is the heat released by substances when they condense from a gas to a liquid.

When materials take in heat to change states of matter, the physical change is endothermic. Exothermic reactions occur when chemicals release heat into the surrounding environment.

Sources:

Related Questions

• A: The specific heat capacity of a metal (or any other substance) is the amount of heat energy required to increase the temperature of 1 kilogram of the metal... Full Answer >
Filed Under:
• A: The formula for calculating thermal energy is Q = mcΔT, where "Q" represents the thermal energy, "m" indicates the substance's mass, "c" denotes the specif... Full Answer >
Filed Under:
• A: The energy required to change the temperature of a substance with no phase change is known as sensible heat. The change in temperature may come from the su... Full Answer >
Filed Under:
• A: Specific heat capacity is a measure of how much energy must be added to a specific amount of a substance in order to raise its temperature by a single degr... Full Answer >
Filed Under:
PEOPLE SEARCH FOR