when does a chemical reaction happen ?

Question

I am johnny. I want a tutor to answer for me this question.

Answer 1

http://en.wikipedia.org/wiki/Chemical_reaction

 

This is an excerpt from the article.  You will want to put into your own words.  

 

"Chemical reactions happen at a characteristic reaction rate at a given temperature and chemical concentration, and rapid reactions are often described as spontaneous, requiring no input of extra energy other than thermal energy. Non-spontaneous reactions run so slowly that they are considered to require the input of some type of additional energy (such as extra heat, light or electricity) in order to proceed to completion (chemical equilibrium) at human time scales."

 

Hope this helps!