Hi. This is Mr. Andersen. Today I'm going to talk about the properties of
matter. What is matter? Matter is anything that has mass and takes up space. But in this
podcast we're going to talk about large scale measurements of matter. So how large could
we get? Large enough, if we talk about this. This is actually, if we were to look up in
the constellation Pegasus, we'd find this. This is a binary system where we have this
star, which in relation to our sun is much bigger. It's called IK Pegasi B. And then
we have this tiny little thing which is a white dwarf. And what is a white dwarf? It's
essentially a star that's lost enough of its mass or lost enough of its energy to kind
of go dark. The cool thing about white dwarfs, they have always fascinated me, is they have
a huge amount of density. In other words if we were to look at this one white dwarf right
here, it has about 1 times 10 to the 6th grams per cubic centimeter for density. What does
that mean? One cubic centimeter of this would have the mass of 1000 kilograms. So a tiny
little bit like that would weigh 1000 kilograms. So that's pretty amazing. Eventually this
will go red giant. This stuff will go into here and could explode as a supernova. But
I'm getting ahead of myself. So first of all let's talk about what density is. Density
is essentially mass per unit area. And so I like this because it's a quick way to remember
density. I've got M D V here on the bottom. And so let's say we had a cube of water that
looked like this. And that cube of water was 1 centimeter by a centimeter by a centimeter.
So it's 1 cubic centimeter. The mass of that would be, we'll say 1.00 grams. The volume
would be 1.00 centimeters cubed. And so it would have a density of, well let me stop
for a second. Because you can use this pyramid. And so what you do is you simply put your
finger and start at the one that you want to find. And so in this case if I cross out
density, this tells me that the density it simply the mass divided by the volume. And
so if I take the mass, which is one. Divide it by the volume, which is one, it's going
to give me a density of 1, let me scratch that. Get the significant digits right. 1.00
grams per cubic centimeter. Okay. So another thing you could do is let's say, I'm given
the density but I want to find the mass. That mass is simply going to be the density times
the volume. Or scratch that. If we want to find the volume, I cover that up. And that's
going to be mass divided by the density. So that's pretty cool. What do we know about
water? Water is something that's really weird. And so if I were to have that same cube of
water and put it in an ice cube tray, it would actually increase the volume. So the volume
would be greater than one. And that's because ice actually has a density of 0.92 grams per
cubic centimeter. That's why ice floats. But we'll talk more about why it actually does
that later. So now we're presented with the idea of Archimedes. Archimedes had this dilemma.
The king told him that he wanted him to figure out if the crown that he asked the craftsman
to make was actually made of gold. Or if the person had actually slipped in some silver
to save himself some money. And so the story goes that Archimedes thought about this for
a long period of time. And then eventually he's taking a bath and he realizes the right
answer and how to solve it. And he jumps out of the bath and runs through the streets saying
"Eureka!" In other words "I've discovered it." And so what did he discover? It's a pretty
cool idea. He discovered Archimedes Principle. And so Archimedes Principle goes like this.
What he discovered or his idea is that he could have a balance where on one side of
that balance he puts the crown. So let's put the crown like this. And then on the other
side of the balance he puts a weight of the correct amount of gold. And then he just kind
of balances this whole thing in water. And so what he could look at is the buoyant force.
In other words, in a perfect world the buoyant force of the gold and the buoyant force of
the crown will be the same. But if it's somehow unequal, then he knows that the guy is trying
to cheat the king. Okay. So what is buoyancy? Buoyancy is simply is, a way to think about
it is it's a fluid that that you're immersing something in saying, I don't want this. I'm
trying to throw it out. And so an example, this right here, this oil tanker is made of
steel. And steel is going to sink. We know that. And so how is this oil tanker able to
float? Well that oil tanker is displacing water. And by displacing the water the water
is exerting a force on that we call the buoyant force up. And so this is a little bit better
job than that. When you put an object in water, there's a force of gravity pushing it down.
But there's also a buoyant force equal to the weight of the fluid you displace. And
so by making the volume bigger. In other words decreasing the density, we could make something
float that normally wouldn't. So that's buoyancy. Buoyancy and gases works a little bit differently.
Buoyancy of gases is a direct relationship. And now we have one of our first laws that
you should remember. This is Charles Law. Charles Law says this. That as you increase
the temperature, there's going to be a direct relationship with the volume. And so if we
look at this apparatus over here, if I were to somehow crank up the temperature in here,
that's going to make the molecules move around more quickly. And that's going to increase
the volume. And so an example of this, this is my friend Scott Taylor. He's go a balloon
in town. And as he heats up this balloon he increases the volume of it which decreases
the density. And that makes it float. If he wants to come down when he's done with the
balloon trip, all he does is quit firing that propane tank into it. And that's going to
decrease the volume and thereby decrease the density. And so it's going to sink. So Charles
Law there is a direct relationship between volume and temperature. Next thing I should
explain is what's called pressure. Pressure, think about it like this. Inside an object
pressure is the force of all those molecules pushing out on it. And so the SI unit for
that, in other words in science we measure that in something called a pascal which is
named after this guy Blaise Pascal. What is it? It is the force of one newton. And a newton,
the way I always like to remember a newton, a newton is like the weight of one apple.
The weight of one apple on one meter cubed. And so a newton is not very big. So normally
we measure instead of pascals we measure in kilopascals. Which is going to be 1,000 pascals.
And so the best barometer or the most simple barometer, all you do is in a tank you put
some mercury. And that mercury goes up a tube like this. And so as the, let me change color
for just a second, as the air pressure pushes down on it, it pushes that mercury up in the
tube. And so it's a way to measure air pressure. And air pressure is incredibly intense. We
don't normally notice it. And that's because we just are surrounded by it. But imagine
if we go deep down in the ocean, that pressure is big enough that it can actually crush us.
So that's pressure. But it finally brings us to what's called Boyle's Law. And Boyle's
Law says this. If we've got pressure and volume, we'll say right here. And we increase the
volume. So we're going to increase the volume of that object. What happens to the pressure?
The pressure is actually going to decrease. Or a better way to think of it. If we have
all of this gas, it's got a really big volume. But we were to somehow squeeze it into this
little aerosol canister, which has a smaller volume, then it's going to have a way greater
pressure. And so it's going to exert that pressure out. So Boyle's Law looks like this.
In other words, as we increase the volume we're going to decrease the pressure. Likewise,
if we have a given amount and we decrease the volume, then we're going to increase that
pressure. And so these are simple ones that you can actually solve some quick equations
if you know Boyle's Law. The 1 and the 2 represent the pressure and the volume initially and
then after something happens. Okay. Last thing I want to talk about is called viscosity.
Viscosity is resistance to flow. And so resistance to flow in a material. In other words something
that has a really high viscosity would be silly putty. Something that has a really low
viscosity is going to be water. In other words it easily pours. Something that has a viscosity
somewhere in the middle is going to be honey. I love this picture right here. What they've
done is they've actually taken some silly putty. And if you put that silly putty on
a table with a small hole in it, it will eventually, since it has really high viscosity, will flow
through here. And so you get kind of this drooping thing coming through it. One interesting
thing I learned when I was growing up is that windows, the glass that we used to put in
windows is a really, the glass is actually a liquid. It's a really high viscosity liquid.
And so if you go to old windows in old houses you'll find that they're actually thicker
at the bottom. And that's because the glass is actually slowly oozing down to the bottom.
And so those are some of the properties of matter. Big things we talked about again is
Archimedes Principle and buoyancy. But also Charles Law and Boyle's Law. And so hopefully
that's helpful.