In this video we are going to look at exothermic and endothermic reactions.
So what are they? how are they different?
What about their energy levels?
In the next couple of minutes you’ll know everything you need to get started.
An exothermic reaction gives off energy to the surroundings,
like this fire giving off heat.
Whereas an endothermic reaction takes in energy from its surroundings,
like this pool melting snowman taking in the heat.
Just remember Exo means external so giving out,
Endo means internal so taking in.
Let’s start by having a quick look.
Because exothermic reactions transfer energy to the surroundings
and this energy is usually heat energy.
They cause the surroundings to heat up
Just like a bonfire keeping everyone warm.
Other examples of exothermic reactions are
the neutralization reactions between acids and alkalis,
the reactions between water and calcium oxide and respiration.
It is easy to detect exothermic reactions
Just get your thermometer and see if the temperature increases
Watch the hydrochloric acid and sodium hydroxide solution being mixed
and see how the thermometer increases
most chemical reactions are exothermic because heat is given out
physical processes can also be endothermic or exothermic
When something freezes it goes from liquid to solid
Bonds need to be made for this to happen
and to make bonds you need to do some work
Thus energy is given out and freezing is exothermic
Similarly when condensation happens because a gas is going to liquid
Again bonds need to be made
so energy is given out
so freezing and condensation are both exothermic
Because in exothermic reactions energy is given out to the surroundings
This means that energy of the reactants is higher than the energy of the products
hence the energy curve for the exothermic reactions will look like this
Now let’s have a look at endothermic reactions
These are less common
Remember that endothermic reactions take in energy from the surroundings
Again as with exothermic reactions the energy being transferred is usually heat
So in endothermic reactions the surroundings usually get colder
Again, we can detect endothermic reactions with a thermometer
because the temperature would get colder
some examples of endothermic reactions are electrolysis
the reaction between sodium Carbonate and ethanoic acid and photosynthesis
Endothermic reactions can also be seen in physical processes
where something melts it goes from a solid to a liquid
For this to happen bonds need to be broken
and to break bonds energy to be put in like our melting snowman
Boiling is also endothermic
because energy needs to be put in to break the bonds from liquid to turn to gas
because in endothermic reactions energy is added to the reaction
the energy of the products is higher than the energy of the reactants
So the energy curve looks like this
so there you have exothermic and endothermic reactions
All you need to remember is that exothermic reactions give out energy
endothermic reactions take in energy
both can be detected with a thermometer
In exothermic reactions the surroundings get hotter
and in endothermic reactions the surroundings get colder
exothermic reactions start with more energy and end with less
while endothermic reactions start with less energy and end with more
Freezing and condensation are exothermic
because bonds need to be made which gives out energy
Melting and boiling are endothermic
because bonds are broken which requires additional energy
think of the snowman again
and finally Exothermic reactions are more common