Onion Experiment for Kids – Why Onions Make You Cry!

Here is a simple experiment with onions for children that will not only answer the question “Why onions cause tears”, but also help you find ways to avoid tears.

This simple onion science experiment is perfect for kids of all ages, whether they’re toddlers or teenagers. Children will learn interesting scientific facts, and adults will receive useful tips on how to avoid tears while cutting onions.

But first, let’s deal with the scientific aspects of onions and tears.

Why onions cause tears

Onions contain sulfur amino acids. When you slice an onion, you break down its cells, releasing enzymes that react with the sulfur amino acids in the onion to form a volatile gaseous compound called propanethiol S-oxide.

This gas is the cause of irritation and burning in the eyes. But before you think it’s propanethiol S-oxide that makes you cry, it’s not! It’s actually your body’s self-defense mechanism that makes you cry.

Your amazing body goes into action when propanethiol S-oxide reacts with the moisture in your eyes, irritating them. To wash this irritating gas out of the eyes, the brain triggers lacrimation, which causes the eyes to water.

So it’s not actually an onion! This is our amazing defense mechanism in action!

Quick tip: While onions may make you cry, these funny science jokes are sure to cheer you up!

Simply put, without any heavy scientific terminology, tears are our body’s way of washing away the sulfur-containing gas released by onions.

Interesting fact: tears are produced by the lacrimal glands located above the eyelids towards the outer edge of the eyes.

Great, isn’t it? How the simple process of slicing an onion triggers our defense mechanism and has so much science behind it. To explain this to your child, you can omit the name of the gas and just mention that onions release a gas that irritates our eyeballs, making us cry.

An experiment with onions for children

Here’s a simple onion experiment that will help your kids (and you!) find smart ways to avoid the irritant and, consequently, the tears.

You will need:

• Onion
• Laboratory glasses – swimming glasses are also suitable!
• Boiling water
• Than
• Cutting board
• Observation Sheets – Use the free printables at the bottom of the page

Scenario A: Have your child put on lab glasses or swim goggles and cut an onion. Invite the younger children to stand next to you while you chop the onion.

Scenario B: Take another bulb, put it in the refrigerator and let it cool for 10 minutes. Now cut the bulb without wearing safety glasses.

Are your eyes watering again? If so, did they tear as much as when cutting onions at room temperature?

Option C: Take a pot of boiling water and put the onion in it for 10 minutes. Cut it and record your observations.

Wearing laboratory glasses prevents gasses released during cutting from coming into contact with the eyes. Therefore, in this case, the eyes do not water.

Temperature also affects the amount of gas released by onions, so cold onions may not cause as much tearing.

Discuss your findings with your child and ask her if she can think of any other ways to keep her eyes from watering when chopping onions. Who knows, you might discover a new way to avoid onion-induced tears!

Sheets for observing the onion experiment

And before you go, here are some fun facts about onions for you!

Do you like interesting facts? Dive into our list of 229 amazing facts for kids.

Source: Onion Experiment for Kids – Why Onions Make You Cry!