The term endothermic describes a process or reaction in which the system absorbs energy from its
surroundings in the form of heat. The intended sense is that of a reaction that depends on taking in heat
if it is to proceed. The opposite of an endothermic process is an exothermic process, one that releases,
"gives out" energy in the form of heat. Thus in each term (endothermic & exothermic) the prefix refers
to where heat goes as the reaction occurs.
Endothermic Reaction Examples
An endothermic reaction is any chemical reaction that absorbs heat from its environment. Here's a list
of examples of endothermic reactions. You can use these when asked to cite an example or to get ideas
to set up a demonstration of an endothermic reaction or process.
e.g: photosynthesis (chlorophyll is used to react carbon dioxide plus water plus energy to make glucose
and oxygen)
Endothermic Processes
These examples could be written as chemical reactions, but are more generally considered to be
endothermic or heat-absorbing processes:
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melting ice cubes
melting solid salts
evaporating liquid water
converting frost to water vapor (melting, boiling, and evaporation in general are
endothermic processes)
 forming a cation from an atom in the gas phase
 splitting a gas molecule
 separating ion pairs
 cooking an egg
 baking bread
Examples of Endothermic and Exothermic Processes
Photosynthesis is an example of an endothermic chemical reaction. In this process, plants
use the energy from the sun to convert carbon dioxide and water into glucose and oxygen.
This reaction requires 15MJ of energy (sunlight) for every kilogram of glucose that is
produced:
sunlight + 6CO2(g) + H2O(l) = C6H12O6(aq) + 6O2(g)
EXOTHERMIC REACTION :
An exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the
opposite of an endothermic reaction.
The term exothermic ("outside heating") describes a process or reaction that releases energy from the
system, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity
(e.g. a battery), or sound (e.g. explosion heard when burning hydrogen).
After an exothermic reaction, more energy has been released to the surroundings than was absorbed to
initiate and maintain the reaction. An example would be the burning of a candle, wherein the sum of
calories produced by combustion (found by looking at radiant heating of the surroundings and visible
light produced, including increase in temperature of the fuel (wax) itself, which with oxygen, have
become hot CO2 and water vapor,) exceeds the number of calories absorbed initially in lighting the
flame and in the flame maintaining itself.
An exothermic reaction is a chemical or physical reaction that releases heat. It gives out energy to its
surroundings. The energy needed for the reaction to occur is less than the total energy released.
Some examples of exothermic processes are:
Explosions are some of the most violent exothermic reactions
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Condensation of rain from water vapor
Combustion of fuels such as wood, coal and oil
Mixing water and strong acids
Mixing alkalis and acids
The setting of cement and concrete
Exothermic processes
Endothermic processes
making ice cubes
melting ice cubes
formation of snow in clouds
conversion of frost to water vapor
condensation of rain from water vapor
evaporation of water
a candle flame
forming a cation from an atom in the gas phase
mixing sodium sulfite and bleach
baking bread
rusting iron
cooking an egg
burning sugar
producing sugar by photosynthesis
forming ion pairs
separating ion pairs
Combining atoms to make a molecule in the
gas phase
splitting a gas molecule apart
mixing water and strong acids
mixing water and ammonium nitrate
mixing water with an anhydrous salt
making an anhydrous salt from a hydrate
crystallizing liquid salts (as in sodium
acetate in chemical handwarmers)
melting solid salts
nuclear fission
reaction of barium hydroxide octahydrate
crystals with dry ammonium chloride
mixing water with calcium chloride
reaction of thionyl chloride (SOCl2) with
cobalt(II) sulfate heptahydrate