system
Given the following post, respond as if you're commenting on Reddit:
human
Why does boiling oil make food crispy yet boiling 
water softens the food? 

My curiosity is killing me with this. I noticed this when one time I deep fried my fies and they got crispy. Meanwhile I boiled potatoes and they got soft. Does the thickness of the 2 liquids have anything to do with how it effects the food? Is it a chemical reaction? Does the tempurature effect it?
gpt
Water boils at 100 degrees Celsius which means that when you poach the food (or use a bain-marie), the food can only reach that temperature but no more.  This temperature is not high enough to cause any browning reactions and will take a long time to dry out the food.

Oil and fat can reach a much higher temperature and therefore will rapidly dry out and crisp anything in direct contact with it.  It will also brown the food which is a result of either a Maillard reaction or caremalisation.  Note that these browning reactions can be caused by air, steam, (e.g. in an oven), radiation (broiler/grill) or direct contact with hot metal (flame grill, or making caramel directly in pan) as well.