Condensation is a change of state from the gas to the liquid phase. Most frequently refers to the conversion of water vapor to liquid water, which happens for example on cold surfaces or in nuclei in the atmosphere.
Condensation is also an example of a phase transition. The reverse process (transformation of liquid into gas phase) is called vaporization.
Endothermic phase transitions take energy, in the form of heat, from the environment. Exothermic phase transitions release heat to the environment.
Condensation releases heat to the environment, so it is exothermic. During condensation, the molecules lose kinetic and potential energy, which is released as heat (thermal energy).
Evaporation is the opposite of condensation. Thus, evaporation is an endothermic process. When molecules are in the liquid state, they are close together and attracted to each other. Energy, in the form of heat, must be given to separate them, so evaporation is an endothermic process.
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What is the Endothermic and Exothermic Process?
Endothermic means that the transition takes heat (thermal energy) from the environment. Exothermic phase transitions release heat (thermal energy) into the environment.
Examples of endothermic transitions are the boiling of water and the melting of ice, which take heat from the environment.
Exothermic transitions are the condensation of water vapor and the freezing of liquid water, that gives heat to the environment.
| Table 1. Comparison of exothermic and endothermic. | ||
| Comparison parameters | Exothermic process | Endothermic process |
| Definition | A process that releases energy in the form of heat to the environment. | A process that takes energy in the form of heat from the environment. |
| Enthalpy variation | Negative (heat released to the environment) | Positive (heat taken from the environment) |
| Energy | Energy is released into the environment. | Energy is taken from the environment. |
| Examples | Condensation, Freezing, Deposition | Vaporization, Melting, Sublimation |
What is Condensation?
In condensation, the molecules, initially separated in the gas phase, get closer and form a liquid (denser phase).
Condensation is commonly observed on cold solid surfaces, for example, refrigerated metal cans and inside glass windows in winter.
Also, the condensation of water vapor on the small particles of dust in the atmosphere produces clouds. Under freezing temperature conditions, atmospheric water vapor condenses to snow (the solid phase) and the process is called deposition.
Does Condensation Absorb or Release heat?
Condensation releases heat because the molecules lose kinetic and potential energies that are released as heat to the environment.
An example is the condensation of water vapor.
Why is Condensation Exothermic?
The molecules in the gas are separated by great distances (in relation to their size). They move in straight lines until they collide with another molecule or the wall of the container. So, the gas molecules have kinetic energy.
The molecules in the liquid phase are closer together and move slower than those in the gas phase.
Thus, in condensation, the gas molecules lose kinetic energy when going into the liquid state. The lost kinetic energy is released to the environment in the form of heat.
Also, the molecules in the liquid are close, there is a force of attraction between them. This means that the liquid has lower potential energy than the gas. This potential energy is lost by the gas molecules and is also transferred to the environment as heat.
The loss of kinetic and potential energy, released in the form of heat, makes condensation exothermic.
When vapor comes in contact with the surface of an object kept at a temperature lower than the saturation temperature, it condenses into a liquid with the release of heat, called latent heat. This process finds use for heating.
The reverse process (evaporation) takes thermal energy from the environment and is applied to refrigeration.
Thus, the reaction from left to right (Condensation) is exothermic, and from right to left (Evaporation) is endothermic.
The Phase Changes of Water. Which are Exothermic, and Which are Endothermic?
Variations in pressure or temperature produce phase changes. The phase changes can be seen in a phase diagram. A phase diagram for water is shown below, with the corresponding changes.
Figure 1. The phase diagram for water
Thus, as seen in the diagram, the transition from gas to liquid is called condensation, and the inverse vaporization. From solid to liquid is called melting, and the inverse freezing.
The direct transformation from solid to gas is called sublimation, and inverse deposition. The deposition is a type of condensation. Frost and snow are examples of deposition.
In Figure 2 we see the liquid and gas section of Figure 1.
Figure 2. A section of the phase diagram for water
At points A and C, liquid and gas are at equilibrium. At point B, only the gas (vapor) is present, and condensation is not possible.
To have condensation at constant pressure P, the temperature may be lowered from B to A; and for doing condensation at constant temperature TB, pressure has to be increased from B to C.
The Heat of Condensation
The heat of condensation is defined as “the heat evolved when a vapor changes to a liquid”. More specifically, “the quantity of heat that is evolved when the unit mass of a vapor is changed at a specified temperature to a liquid and that equals the heat of vaporization” (Merriam-Webster).
The heat added or removed during a phase change is called “latent heat”.
The heat of condensation is equal to the heat of vaporization with the opposite sign. The heat of vaporization is always positive and the heat of condensation is always negative.
The heat of condensation is equal to the change of a thermodynamic property called enthalpy, represented by H:
ΔH = Hliquid – Hgas
The gas and liquid are at the same conditions of pressure and temperature.
In general, If heat is absorbed during the process, ΔH is positive; if heat is released, then ΔH is negative.
Enthalpy of Condensation
The enthalpy of condensation is equal to the heat of condensation, which is always negative because heat is released into the environment.
The enthalpy of evaporation is always positive because energy (in the form of heat) is needed to separate the molecules. Enthalpy of evaporation and enthalpy of condensation have the same absolute value, but different signs.
The stronger the attraction between the molecules, the higher the energy needed for separating them, and the higher the enthalpy of evaporation. The enthalpy of evaporation is dependent upon pressure.
Enthalpies are measured in units of energy per mole, or Joule/mol. Table 2 shows enthalpies of condensation at pressure = 1 atm for a series of liquids:
| Table 2. Enthalpies of condensation at normal pressure (P = 1 atm). Data from Wikipedia | ||
| Compound | Boiling point, °C | Enthalpy, J/mol. |
| Methane | -161 | -8170 |
| Propane | -42 | -15700 |
| Butane | -1 | -21000 |
| Methanol | 64.7 | -35200 |
| Ethanol | 78.37 | -38600 |
| Water | 100 | -40660 |
Molar Heat of Condensation
The molar heat of condensation is the heat evolved when one mole of vapor is condensed. One mole is equal to 6.02214076×1023 molecules, or a mass in grams equal to the molecular weight in daltons.
In the case of water, whose molecular weight is 18.015 daltons, the mass of a mole is 18.015 grams.
The value of the molar heat of condensation is equal to the enthalpy (Table 2) with the changed sign. So, the molar heat of condensation for water at P = 1 atm and T= 100 °C is 40660 J/mol.
What Conditions Cause Condensation?
Condensation occurs when warm, moist air collides with cold surfaces. When this moisture-packed warm air comes into contact with a chilly surface, it cools down quickly and releases the water, which turns into liquid droplets on the cold surface.
Examples are water condensing on a cold beer can, glass windows in winter, walls, mirrors, and eyeglasses.
Clouds form in the upper atmosphere when the invisible water vapor rises from the earth’s surface and temperature drops.
Water then condenses in the always present small particles, like dust. The droplets may then coalesce to produce rain drops. The condensation at low altitudes is similar but it is called fog.
FAQs
Is Condensation a physical change or a chemical change?
Condensation of molecules is a physical change. Chemical changes involve dissociation and/or the formation of chemical bonds.
For example, no chemical bonds are formed or broken in the condensation of water vapor. Chemical changes occur in chemical reactions, where new molecules are formed.
Is Sublimation endothermic or exothermic?
Sublimation is endothermic because the environment gives energy (in the form of heat) needed for separating the molecules in the solid and increasing their kinetic energy.
An example is the direct transformation of frozen water to vapor.
Is Evaporation endothermic or exothermic?
Evaporation is endothermic because energy (in the form of heat) is needed for overcoming the forces of attraction between the molecules and for increasing their kinetic energy.
What processes use evaporation and condensation?
• Solar desalination.
In solar desalination, water is heated by the sun in a specially designed still, and the vapor is condensed on a cold surface. This method does not need another source of energy, like distillation followed by condensation.
• Refrigeration and air-conditioning.
A cycle including evaporation and condensation of a special fluid (generally tetrafluoroethane) is used for refrigeration and air-conditioning.
The evaporation part, being endothermic, takes heat from the environment thus lowering the temperature.
• Heat pumps
Heat pumps also use evaporation and condensation cycles to transfer heat from the outside to houses and buildings using evaporation-condensation cycles.
They consume less energy than other heating systems. Heating pumps can also be used for cooling.
Condensation is exothermic (it gives away energy in the form of heat). The heat comes from the kinetic and potential energy of the molecules.
As a result, the change of a property called enthalpy is negative – the enthalpy of the condensed mass decreases in the process. The enthalpy change is measured in units of energy/mass, frequently J/kg or J/mol.
An important example of condensation is the condensation of water vapor or moisture.
FAQs
Is condensation reaction endothermic or exothermic? ›
For condensation the molecules are giving up their heat energy. When molecules give up heat energy, it is called exothermic. Condensation would be exothermic.
Is condensation an endothermic reaction True or false? ›Hence option (C) is correct, Condensation is a process in which heat is released. So, it is an exothermic process.
Is condensation of rain from water vapor endothermic or exothermic? ›2) Rain: Condensation of water vapor into rain releasing energy in the form of heat is an example of an exothermic process.
Is Melting condensation endothermic or exothermic? ›Melting is an endothermic process. Energy has to be absorbed to melt a solid. Condensation is an exothermic process. Energy is removed from a gas slowing the molecules' kinetic energy to condense it into a liquid.
Is condensation endothermic or exothermic quizlet? ›Condensation, freezing, and deposition are exothermic. Vaporization, fusion, and sublimation are endothermic.
Is condensing steam endothermic or exothermic? ›Therefore, we can conclude that as the molecules of water vapour condenses into liquid, it loses energy in the form of heat and thus, the process is an exothermic process.
Is condensation exothermic or exothermic? ›Fusion, vaporization, and sublimation are endothermic processes, whereas freezing, condensation, and deposition are exothermic processes.
What type of reaction is condensation? ›In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a dehydration synthesis.
Why is condensation and freezing exothermic? ›If heat is removed from a substance, such as in freezing and condensation, then the process is exothermic. In this instance, heat is decreasing the speed of the molecules causing them move slower (examples: liquid to solid; gas to liquid). These changes release heat to the surroundings.
Does condensation require heat? ›In order for condensation to happen, the water vapor molecules must release energy so that they can slow their movement. (This energy is hidden and is therefore called latent heat.)
Is freezing condensation or exothermic? ›
When water becomes a solid, it releases heat, warming up its surroundings. This makes freezing an exothermic reaction.
What happens to heat during condensation? ›As condensation occurs and liquid water forms from the vapor, the water molecules become more organized, and heat is released into the atmosphere as a result.
Is freezing and condensing endothermic or exothermic? ›Condensing and freezing, we have to take heat out. It's exothermic.
Is evaporation and condensation endothermic? ›Evaporation is an endothermic reaction because water molecules must absorb heat from the surroundings to increase their kinetic energy and change them to vapours.
Why is condensation Endergonic? ›The condensation of ATP is endergonic. This means that it requires energy input in order to attach a phosphate group to ADP to make ATP. This is because the bond between phosphate groups from ADP to ATP is high-energy, creating a substance that is higher in energy than ADP.
Is condensation a thermodynamic? ›Thus ultimately condensation is a thermodynamically nonspontaneous process forced by super-moist-adiabatic lapse rates. Yet water vapor plays vital roles in atmospheric thermodynamics and kinetics.
Is condensation a heat transfer? ›Condensation represents the change of phase from the vapor state to the liquid state because of cooling. It is considered one of the most important heat-transfer processes in many energy-conversion systems, such as electric power generation plants.
Is condensation positive or negative enthalpy? ›The enthalpy of condensation (or heat of condensation) is numerically exactly equal to the enthalpy of vaporization, but has the opposite sign: enthalpy changes of vaporization are always positive (heat is absorbed by the substance), whereas enthalpy changes of condensation are always negative (heat is released by the ...
Why is water condensing from steam exothermic? ›Liquid water had to have energy put into it to become steam, and that energy is not lost. Instead, it is retained by the gaseous water molecules. When these molecules condense to form liquid water again, the energy put into the system must be released. And this stored energy is let out as exothermic heat.
Is water condensing on a cold surface endothermic or exothermic? ›Condensation is an exothermic process, but in contrast to a bonfire, condensation is not so obviously exothermic because it does not release heat in a way that is easy to sense or observe. Objects in motion have kinetic energy related to this motion, and water molecules are no exception.
What is condensation short answer? ›
Condensation is the process where water vapor becomes liquid. It is the reverse of evaporation, where liquid water becomes a vapor. Condensation happens one of two ways: Either the air is cooled to its dew point or it becomes so saturated with water vapor that it cannot hold any more water.
What best describes condensation reaction? ›A condensation reaction is a reaction in which two molecules combine to form a single molecule. A small molecule, often water, is usually removed during a condensation reaction.
What happens in condensation reaction? ›Condensation reaction: A reaction in which two or more molecules combine to form a larger molecule, with the simultaneous loss of a small molecule such as water or methanol. While this occurs in many reactions, the term is usually reserved for reactions in which a new carbon-carbon bond is formed.
What energy is released in condensation? ›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.
Why does condensation increase temperature? ›When condensation occurs, the water vapor present in air release the latent heat of condensation which is given to air. Since air absorbs the heat given out, its temperature increases.
Why does condensation happen when it's cold? ›Condensation forms when warm, humid air contacts a cold surface. Moisture is in the air all around us and warmer air can hold more moisture. As air cools, it contracts and its moisture condenses. When the temperature drops, the first place you will see any condensation is on the windows.
What is needed for condensation? ›Two things must be present for condensation to occur: warm moist air, and cool surface temperatures below the dew point. The proper control of these two factors can minimize condensation.
Does heat make condensation happen faster? ›For condensation to occur, molecules of water vapor in the air need to be moving slow enough so that when they collide with other molecules of water vapor, they attract to become liquid water. As the temperature decreases, the rate of condensation increases.
Does heat dry condensation? ›Condensation forms when the indoor temperature is warm and outdoor temperatures are cold. Whilst conventional heating methods may effectively heat your home, they are unable to reduce the amount of condensation produced. Heat pumps are different! Warm air circulates and dries condensation at the same time.
Is cooling evaporation or condensation? ›Cooling. If water vapour (gas) is cooled down, it changes into water (liquid). This change is called condensation.
Does ice form condensation? ›
Pore condensation and freezing is responsible for ice formation below water saturation for porous particles | PNAS.
Which process is exothermic? ›Some examples of exothermic processes are: Combustion of fuels such as wood, coal and oil/petroleum. The thermite reaction. The reaction of alkali metals and other highly electropositive metals with water.
What factors affect condensation? ›Condensation depends upon the amount of cooling and the relative humidity of the air. It is influenced by the volume of air, temperature, pressure and humidity.
Which reaction is a condensation reaction? ›Condensation reaction: A reaction in which two or more molecules combine to form a larger molecule, with the simultaneous loss of a small molecule such as water or methanol. While this occurs in many reactions, the term is usually reserved for reactions in which a new carbon-carbon bond is formed.
Are condensation reactions exergonic or endergonic? ›Condensation reactions, like all biosynthetic reactions, are endergonic.
What is a condensation reaction in science? ›A condensation reaction is a reaction between two reactants that yields one larger product and a second, smaller product such as water.
What is a name for a condensation reaction? ›Condensation reactions are called dehydration synthesis reactions. This is because they involve the combining of molecules with the loss of water.
What is condensation process in chemistry? ›Condensation is the process through which the physical state of matter changes from the gaseous phase into the liquid phase. For example, condensation occurs when water vapour (gaseous form) in the air changes into liquid water when it comes in contact with a cooler surface.
Is freezing and condensation exothermic? ›If heat is removed from a substance, such as in freezing and condensation, then the process is exothermic. In this instance, heat is decreasing the speed of the molecules causing them move slower (examples: liquid to solid; gas to liquid). These changes release heat to the surroundings.
Does a condensation reaction produce water? ›Condensation Reaction– Combining two molecules into a single molecule and releasing a small molecule such as water. Dehydration Reaction– A reaction in which one of the products is water. Often, a condensation reaction will be a dehydration reaction because it produces the small molecule water.
What is the best definition of condensation? ›
: the conversion of a substance (such as water) from the vapor state to a denser liquid or solid state usually initiated by a reduction in temperature of the vapor.
What are the two types of condensation? ›There are two broad categories of condensation nuclei: hygroscopic and hydrophobic. Hygroscopic nuclei are "water seeking" nuclei. Water vapor condenses on hygroscopic surfaces readily even when the relative humidity is considerably lower than 100 percent. Salt is an example of a hygroscopic particle.