sentence: Some reactions are very fast, and others are very slow.
sentences_after: Some happen at different speeds, depending on temperature or other things. For example, wood does not react with air when it is cold, but if it is made hot enough, it will start to burn. Other reactions such as Nuclear Reactions differ in the way that Nuclear Reaction does not need a catalyst. They also cannot be stopped, sped up or slowed down.
concept_name: reaction
headings: Chemical reaction
categories: Chemistry