Bubbles

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You would think that bubbles are fragile and all of them can be popped with a simple breeze. But they can be stronger than you might think.

They exist due to a physical property that we call surface tension. Surface tension is created from the difference between the forces of attraction between water molecules and the forces of attraction between those water molecules and the surrounding air. Said another way, if the water was more attracted to the air than other water molecules, bubbles couldn’t exist. It is because air and water do have some atomic attraction to each other that bubbles pop after some time. Naturally, the less air touching the bubble, the more stable it is. Therefore, things that experience surface tension typically like to be smaller to maintain stability, or, in other words, have less surface area.

This is like having the choice between a sugary snack and a nutritious one. According to who you are, you’re going to naturally gravitate toward one of these two and adhere to that diet. But you might get a craving after some time, and you may reach for the other snack that you rarely ever eat. The disturbance causes your balance to shift.

The bubbles you play with in those containers at stores, however, are not just water. They include a detergent like soap. Soap bubbles are different than simple water bubbles. In fact, soap can attach itself to both water and substances like oil, making it amphipathic. Basically, soap molecules have two sides to them, each being attracted to a specific type of molecule. That creates a problem in something uniform like a film of water. Since there is a side to soap that will not accept a bond with water molecules, surface tension decreases, and the bubbles are more likely to pop in the presence of air.

But what happens when you add a molecule of the same type as water? Glycerin falls under this category. Glycerin, or glycerol is actually found in the body fat of humans and animals in very large quantities, but it’s also in vegetable fat and sweeteners. That’s right, it’s that vegetable oil you have in your cupboards and also in corn syrup. Naturally, using something that loves to bind with water molecules will make a stronger attractive force and increase surface tension, preventing it from popping in air.

You shouldn’t have any problem playing with them now.

Matthew Brown

Flux’s founder, chief writer and proud science communicator.

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