Now that winter’s here, the weather fiends out
there are waiting for the next big snowstorm.
But before the flakes fall, armies of trucks
are loaded full of one of the most important
road safety tools out there – salt.
Along with keeping our french fries on point,
salt, like sodium chloride,
has actually saved a lot of lives,
and probably even more fenders thanks
to its incredible deicing abilities.
(REACTIONS SPLASH)
So here’s a truck throwing salt
all over a wintery road.
Like everything else in the picture,
you can bet that that salt is pretty cold.
This begs the question – how be that
something that isn’t hot is melting the ice?
Turns out, salt isn’t actually about melting.
It’s all about freezing.
The freezing point of pure water rests at
32 degrees Fahrenheit, or 0 degrees Celsius.
When the temperature of water reaches
the freezing point, its normally
free-flowing molecules get trapped
into an organized crystal structures.
This is how ice is formed.
Salt disrupts this process.
Upon hitting water,
salt breaks up into two ions:
one sodium and one chloride.
These two ions then move around
and take up space in between
water molecules, pushing them apart
and frustrating their potential
links to form ice. This disruption
is called freezing point depression.
So to put it simply, salt lowers
the freezing point of water.
But there’s a limit.
Salt can only act as a stable
deicer in temperatures above
16 degrees Fahrenheit (-9 C).
And there’s another drawback to salt.
Considering that over 20 million tons of
road salt is used annually in the U.S.,
all that salt has to go somewhere in the spring.
Of those two ions split from dissolved salt,
the chloride ions can have a potentially
negative effect on the environment.
Chloride can kill small aquatic critters,
dehydrate and kill plants,
alter the composition of ground soil
near roads, and can limit water
circulation that keeps lakes healthy.
All that salt is also corrosive to metal,
wreaking havoc on infrastructure.
And oh yeah, your wheels too.
For these reasons, Sand is used as
an abrasive for an alternative.
Sand is often used because it’s
cheap and maybe cuz folks want
to avoid the chloride issues.
The thing is, salts have a
chemical advantage: because you get
2 or more ions when they dissolve,
you get way more melting power
for the same handful of deicer.
So sand might be cheap, but you have
to use way more of the stuff, and
that can leave quite the mess.
Now for super cold temperatures,
sodium chloride in sand won’t do the job.
Some alternatives that melt ice better
include Magnesium Chloride, Calcium Chloride,
Potassium Chloride, and Potassium acetate.
Potassium acetate is particularly incredible
at deicing because it works at temperatures
as low as -75 degree Celsius, while the rest
of the bunch work around the -20 degree mark.
Although these alternative chemicals
are better at deicing at lower
temperatures, most of them have that
environment damaging Chloride too,
not to mention that they cost
way more than that table salt.
And if you’re buying 20 million
tons a year of the stuff… well,
that’s a lot of money!
So people, keep your eyes on the road, and
thank salt for the fine driving conditions.
Or, on the other hand, you can shake
your fist at it, if you didn’t get
that snow day you know you DESERVE.
Make sure to check out this video
on how artificial snow is made,
and because we’re talking about
ice here, check out this one about
mind-bogglingly interesting crystal facts.
Thanks for watching folks, Don’t forget
to subscribe and we’ll catch you soon.