Chemistry C2 5.1

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Whenever chemical reactions take place, energy is involved. That's because energy is always transferred as chemical bonds are broken and formed. 

Some reactions transfer energy from the reacting chemicals to the surroundings. We call these exothermic reactions. The energy transferred from the reacting chemicals often heats up the surroundings. This means that we can measure a rise in temperature as the reaction happens. 

Some reactions transfer from the surroundings to the reacting chemicals. We call these endothermic reactions. Because they take energy from their surroundings, these reactions cause a drop in temperature as they happen. 

Q. What do we call a reaction that gives out heat?

A. An exothermic reaction.

Q. What do we call a chemical reaction that absorbs heat from its surroundings?

A. An endothermic reaction.

Exothermic reactions

Feuls burning are an obvious example of exothermic reactions, but there are others which we often meet in the chemistry lab.

Neutralisation reactions between acid and alkali are exothermic. We can easily measure the rise in temperature using simple apparatus. 

Similarly, heat is released…

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