Fun Video: Solutions Video Lecture - Class 9

[INTRO MUSIC]
Summertime is picnic time, with sweet iced
tea, and yummy fruit salad — and ants —
but still, yummy fruit salad!
And hey, did you notice something?
Those foods have something in common:
they're both mixtures — things made by
combining two or more different things.
Not the ants — they're just ants, but the
iced tea and the fruit salad are mixtures.
Anytime you combine two different
things, you make a mixture;
whether it's strawberries and bananas,
raspberries and blackberries,
or cantaloupe and Legos, which I don't recommend
eating — at all — I'm just saying it's a mixture.
So let's have a little science with our picnic, shall we?
Let's talk about the different kinds
of mixtures we can discover.
For example, if we mix sand and
water in a glass we'll get a mixture,
even though after a while the sand
will settle to the bottom of the glass,
but if we stir some sugar into the water, the sugar
looks like it disappears, but it really doesn't!
The particles that make up sugar
become distributed, or spread around —
evenly among the particles that make up water.
We call this kind of mixture a solution.
Solutions have two main parts:
the solute, which is the stuff that
dissolves — in this case the sugar —
and the solvent, which is the stuff in which
the solute dissolves — in this case, the water.
Now, solutions can be made from types
of matter that are in different states, too,
for example, the air that we breathe
is made up of a solution of gases,
mostly nitrogen, oxygen, and carbon dioxide.
And soda water is really a solution
of carbon dioxide gas in liquid water,
but no matter what — and this is important —
mixing things together in solutions
does not make a whole new substance.
Solutions can be separated again, back
into the substances that made them.
So, for example, if you leave
the lid off a bottle of soda water,
the carbon dioxide that's dissolved in the water
will slowly float up to the top and bubble away.
Given enough time, you'll be back to
having plain old water in the bottle
and carbon dioxide in the air as two
separate things not mixed together.
So when you take a sip of your favorite
fizzy drink, you're drinking a solution.
But not all substances dissolve
easily into other substances.
The ability of something to be
dissolved is called its solubility.
Sand doesn't dissolve in water, for instance,
so we say it has low solubility in water,
but sugar dissolves pretty easily, so
sugar has high solubility in water.
Still, no matter how easily something
might dissolve into another thing,
you'll eventually reach the point
where it can't dissolve anymore.
Let's say you pour a whole bunch
of sugar into a small glass of water.
If you keep adding sugar to it to make it even sweeter — and who would blame you for trying? —
you'll get to a point where no more sugar can dissolve. The extra will just sit at the bottom.
This is called saturation: the point at which
no more solute can dissolve into a solution.
Saturation happens when there's just no more
room for the particles that make up the solute —
in this case, the sugar — to squeeze
between the particles of the solvent — the water.
But all of this is making me snacky!
Let's check out our picnic table again and investigate
the different kinds of mixtures we see there.
Let's start with the fruit salad.
That's definitely a mixture of different kinds of fruit.
Is it a solution?
Nope, because the particles that
make it up aren't equally distributed.
I can dip my spoon in there and come up
with nothing but strawberries one time,
and then go back for more and
get a spoonful of only bananas!
How about the sweet tea?
The solution to that question is...
that it's a solution!
Particles of, say water and sugar in the
tea are evenly distributed in the glass.
Every bit contains water AND sugar:
they're spread out evenly.
Now, can the substances that make up our
iced tea solution be taken apart again?
Yep! If we heat the tea so that the water in
the solution changes from a liquid to a gas,
it evaporates into the air, leaving the sugar behind.
So, let's go over what we learned
at our little mixed-up picnic.
A mixture is made by combining
two or more substances.
When the particles that make up the substances are
equally distributed, the mixture is called a solution.
Solutions can be made of substances that are
in the same state of matter, like gases in the air,
or in different states of matter,
like the gas bubbles in soda.
The solute is the part of the solution that is dissolved,
and the solvent is the part
into which the solute dissolves.
And solutions and some other kinds of
mixtures don't always make new substances,
even though it might look that way.
Now, let's enjoy what's left of our
picnic, before the ants carry it all away!
[OUTRO MUSIC]