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→Key Stage 3
: If a '''chemical reaction''' gives off more energy than it needs to start then it is called an [[exothermic]] '''reaction'''. In these '''reactions''' the [[temperature]] increases.
: If a '''chemical reaction''' takes in more energy than it gives out then it is called an [[endothermic]] '''reaction'''. In these '''reactions''' the [[temperature]] decreases.
===Signs of Chemical Reactions===
There are three signs that a '''chemical reaction''' is taking place:
*A colour change.
*A temperature change.
*[[Effervescence]] (bubbles of [[gas]] are given off.
===Examples===