Endothermic Reactions

In the last lesson we discovered that a chemical reaction that gives out energy is called an exothermic reaction.

An exothermic reaction can give out energy in the form of heat, light, or even sound

Some chemical reactions take in energy when they take place
These reactions are called ENDOTHERMIC reactions.

If you dissolve ammonium nitrate in water then the temperature of the reaction mixture falls.
The temperature falls because heat energy is taken in by the reaction mixture. The heat energy is taken from the surroundings.

Dissolving ammonium nitrate in water is an example of an endothermic reaction

 

Fill in these missing words ...

An reaction is one which gives out energy. An reaction, on the other hand, is one which takes in . One example of an endothermic reaction is the dissolving of ammonium in water. When this happens the heat taken in by the mixture causes the to change.

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The chemical formula for ammonium nitrate is NH4NO3
This tells us that ammonium nitrate is a molecule that is made up of atoms of nitrogen, hydrogen, and oxygen.

The chemical formula for water is H2O

 

What sort of reaction gives out energy ?

What sort of reaction takes in energy ?

When ammonium nitrate dissolves what sort of energy is taken in ?

What atom is not in ammonium nitrate ?

What two types of atom make up a water molecule ?

What do you use to measure temperature changes ?

Where does the heat energy come from ?

If you put your hand on the test tube containing the mixture it feels cold. Why ?

If the reaction was carried out in a freezer, what would happen ?

If the reaction was carried out in warm water, what would happen ?

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Many cold packs used for treating sprains and aches are really just a bag of ammonium nitrate and water. When an athlete or sportsperson hurts themselves they mix the contents of the bag together and put it on the painful part of their body. The endothermic reaction takes heat out of their body ... this 'freezes' the painful area.

 

Now fill in these missing words ...

An endothermic is one which takes in energy. This energy is often taken in - in the form of energy. This causes the of the reaction to change. The change in temperature can be measured by a . One example of an endothermic reaction is the dissolving of nitrate in water.

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