Why do onions make us cry? This easy experiment will explain

Have you ever wondered why tears roll down our eyes while chopping onions? Well, there is science behind this. A simple kitchen experiment will help your child understand the reason behind this.  

What you’ll need 

• Onions 
• Lab or swimming glasses 
• Chopping board 
• Knife 
• Boiling water 

How to 

The steps to carry out this experiment are quite easy. Help your kid to follow this. 

• Make sure your child wears his lab or swimming goggles.  
• She should take the chopping board, place it on the kitchen counter, take an onion and start chopping it using the knife. Be vigilant while they are busy chopping the onions to avoid any kind of accidents.  
• Now, ask her to take a second onion and instead of chopping, put it inside the refrigerator and let it cool for around 10 minutes.  
• Once the onion is cold, it should be chopped, but without the eye gear. Chances are that the eyes will not water, or even if they do, it’s not like the time when you chop an onion kept in room temperature.  
• Now, the student needs to take a third onion and put it in a pan full of boiling water for 10 minutes. After this, they should chop it and see if the eyes start to water or not. Chances are, they won’t.  

What happened in the experiment? 
In case of the first onion, the eyes did not water because the lab or swimming glasses acted as a barrier. In case of the second and third onion, the cold and hot temperature ensured that the eyes did not water.  

Onions contain sulphur compounds in them. That is why, when we slice or chop them, the stable molecules of sulphur turn into volatile gas. This, in turn, reacts with naked human eyes and cause irritation. To flush this volatile gas out, the eyes water themselves as a defence mechanism. That is why tears roll down when we chop onions.