Sometimes after a hard day at work I grab a foamy beer and think.
Why dis all foamy?
C'mon scientists.
Luckily, Stanford is on the case!
Hey there everyone, Trace here for DNews.
Researchers at Stanford University have been playing with bubbles, which is a sentence
I can’t believe I get to say.
They’ve found a way to stop the colorful swirling patterns you see on the surface of
a bubble -- they're called eddies.
The colors in those eddies actually correspond to the thickness at that point in the bubble,
and they swirl because of something called the Marangoni Effect -- which is when molecules
that aren’t that attracted to each other in one part of the bubble rush off to areas
where they’re more wanted.
It has to do with the tendency of fluids to move to areas of higher surface tension.
You probably remember surface tension from middle school science; it's why water can
fill just a LITTLE above the top of the glass.
Under the surface water molecules are attracted to all the other water molecules around them,
but the ones on the surface have nothing above them so they cohere (or stick) to their neighbors
more strongly.
This creates the phenomenon of surface tension.
Incidentally, they don’t do it as well when they’re hot, which is why hot water is better
for washing: the water spreads around easier and you literally get wetter.
But that's neither here nor there.
If you really want to mess up the balance you can throw some soap into it.
Soap molecules are kind of shaped like match sticks, they have a head that is all about
water and a tail that takes to water like a cat.
If you plop a drop of soap into the middle of these tense molecules, chaos breaks out.
The soap molecule totally wrecks that surface tension.
Molecules that do this are called surfactants.
When a surfactant breaks the surface tension in one area, they’ve created a surface tension
gradient.
Essentially, water in the low tension area is pulled on by water in the high tension
areas.
This is called the Marangoni effect.
And again, is why the colors swirl around bubbles.
The most visible experiment demonstrating the Marangoni effect that you can do at home
involves milk, food coloring, and a drop of soap.
Place a couple drops of the food coloring of your choice in the middle of a bowl of
milk.
Plop one drop of soap in and then WOOSH!
Marangoni effect.
Again, what's happening is when the water repelling tail of that soapy surfactant finds
the surface, it prevents the water molecules from grouping, and sticks its tail in the
air instead.
Without a mass of water molecules at the surface, we get less surface tension.
And these experiments are just for kids either, the Marangoni effect can have
real world applications…
Or so the Stanford scientists tell us.
When they messed with the Marangoni effect, they found they could stabilize these colorful
eddies on the bubble's surface.
They created a bubble under the water and raised it slowly through the surface
tension to manage the amount of Marangoni effect.
Once everything stabilized, they could raise it a little more, and then a little more!
When one colorful eddy would run into another, they would create a boundary and lock into
place.
No more swirling colors!
But more importantly, they've created a more stable bubble!
And this research does have a practical purpose!
The scientists studying this are experimenting with ways to separate crude oil from water,
or how to rid drug formulations of unwanted bubbles.
Most importantly of all, they’re studying how the structure of bubbles affects the quality
of beer foam.
Listen scientists if you could make a cold one that doesn’t foam over when I set my
bottle down a little too fast, you can play with all the bubbles you like.
Speaking of cold ones, here at DNews, we’ve learned that it’s hard to make videos every
day of the week, let alone doing it for 10 years!
That’s why we want to raise a cold one to congratulate Philip DeFranco on his 10 year
YouTube anniversary!
If you haven’t already, head on over to his channel and send him some love!
The guy really deserves it! 10 YEARS!
So if hot water makes your hands wetter, do you still need to use soap?
Yeah, totally.
I explain why in this video here.
Did you do any other science experiments as a kid that you wanna know the
super complex explanation of? Let us know in the comments and
make sure you keep coming back for more DNews!