Zero vs. First Conditional

• 
• The zero conditional describes what happens in general. It describes facts and truths.

  -If you touch a fire, you get burned.

  (Every time anyone touches a fire, they get burned. It is a fact.)

    
  

  The first conditional describes a particular situation. It describes possibilities that are 100% certain.

  -If you touch the fire, you will get burned.

  (I don't know if you will touch the fire.  If you decide to touch the fire, you will get burned.  It is a possibility.) 

• Zero Conditional	First Conditional
  If you eat spoiled food, you get sick.	If you eat spoiled food, you will get sick.
  Plants die if they don't have water.	Your plant will die if it doesn't have water.

 

Source : Alison