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→About Chemical Reactions
===About Chemical Reactions===
: Most '''chemical reactions''' are irreversible.
: In a '''chemical reaction''' the [[atom]]s rearrange to form a new [[substance]].
: '''Chemical reactions''' often need some [[energy]] to start, like [[combustion]] where the [[fuel]] needs to be [[Heat|heated]] to start.
: 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.
===Examples===