Ah… that’s better.
Now that I’ve had some caffeine, let’s run that back.”
What’s going on in that cup of coffee?
It might seem mundane, but the closer you look, the more complex and beautiful it becomes.
First off, there are trillions upon trillions of molecules in the air around that coffee.
And those hot vapors rising off the cup carry more than a thousand different types of molecules.
A few dozen of those contribute to coffee’s one-of-a-kind aroma.
This pyrazine has an earthy smell.
Methylpropanal is fruity and spicy.
There’s vanillin, you can probably guess what that smells like.
Methional smells like a baked potato.
Methanethiol is the odor of cabbage or garlic--thanks to a sulfur group, which also shows up in
the smells of rotten eggs and skunk spray.
Most of those molecules are made when the beans are roasted.
The heat of roasting provides the energy to convert coffee’s bitter chlorogenic acid
into all these other compounds, making a richly flavorful, fragrant and just awesome beverage.
Many chemical reactions require some energy to get going, even ones that release energy
[show gas stove lighting], like combustion.
After all, spending energy is how we make things happen: cars drive, legs walk, coffee
brews.
Which brings me of course to caffeine, the reason why most of us drink coffee in the
first place.
The story of caffeine is also a story of evolution.
Plants didn’t evolve caffeine to help us get through 9 am meetings.
Like so many of the molecules plants make,caffeine --which is actually pretty bitter on its own
-- is a chemical weapon that can disable or even kill insects that threaten the plants.
But citrus plants use caffeine a different way.
Thanks to caffeine’s memory-boosting and ever so slightly addictive kick, it helps
bees and other pollinators remember the citrus flowers they visit.
That gives those plants an advantage in spreading their genetic material--which is, evolutionarily-speaking,
what life is all about.
So caffeine doesn’t just give you that pleasant morning buzz.
You can also thank it for your orange juice.
But back to our own brains.
Caffeine blocks the nerve receptors that signal the brain that it’s time to sleep.
That’s what helps us power through our bedtime.
Speaking of energy…
Watch that milk swirl and blend with the coffee.
That’s diffusion, the process of particles moving from an area where there is a lot of
the same stuff to an area where there isn’t.
Diffusion is how breathing keeps us alive.
Oxygen diffuses from air into our bloodstream in the lungs, and from capillaries into our
cells throughout the body.
The way the milk moves here is driven by a few things.
It falls due to the force of gravity pulling it down from the carton into the mug.
But then its motion through the coffee is disrupted by the stickiness of milk and coffee
molecules interacting.
That and the walls of the mug help set up those swirling eddies.
Convection is at play here too.
Colder, denser milk sinks to the bottom of the warmer less dense coffee.
This causes the same kind of loops of motion that happen in liquified rock far beneath
earth’s surface.
It’s this motion that keeps our planet geologically active.
Even in the absence of any of these phenomena, milk and coffee will eventually mix anyway.
The particles of milk and little undissolved coffee grounds dance thanks to Brownian motion:
That’s the random movement of particles as they collide off one another.
Studying this dance was one of the clues Einstein used to prove the existence of atoms.
This spontaneous process of mixing follows the second law of thermodynamics: that entropy,
or disorder, increases over time.
Your coffee and milk go from two separate substances to a mixture, which is less ordered
because it’s made of two things all mixed up together.
This disorder increase is even more obvious with the sugar, which goes from a solid, crystalline
state--each molecule locked in a pattern -- to a dissolved form, with sugar molecules all
over the place.
So it goes with the rest of the universe.
Rocks crumble to dust.
Ice melts.
And your place keeps getting messier.
Left to itself for long enough, the entire universe will one day reach a state of maximum
disorder.
A bit like this milk and coffee.
What are we getting at here?
From the largest scale to the smallest, chemistry is everywhere.
And once you see it, you'll never look at the world the same way again.