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alright so here's our notes for today
this is gonna be pretty short don't forget that you can
always pause at any point or if you need to you
catch-up on any the notes or replay if you've missed
anything alright so you should be on page 33
we're gonna look acids bases and pH
scale now you don't need to draw this in your notebook
I just want you to take a look at this this is our water
compound and we know that this is a covalent bond
because of the sharing of electrons but we can also break these bonds apart
kinda what we're talking about today is breaking apart
of bonds in certain solutions
but what's interesting is that when water breaks apart
it doesn't break apart back into its two hydrogens
and oxygen this is in fact called water dissociation and you can write that down
and write this equation down. water breaks apart
or disassociate that's what it means
we actually get some ions we get hydrogen-ion
can we get hydroxide ion and it looks something like
yes remember a thing giving up an electron
and the taking up an electron is what causes those
ions to form. I really don't care if you draw this picture out
just make sure you have that equation written down in your notes. the reason
why I want you to see this
is that when we look at other molecules they can also dissociate
or break apart and if we look at that solution
as it breaks apart if there are more hydrogen ions
this is called acidic solution or
you may have heard it called acid. if there are more hydroxide ions
it is called an alkaline solution or what you may have heard called
base solution. now if the hydroxide
and hydrogen ions are equal then it's considered a neutral solution.
so whenever we look at if the solution is an
acid or a base, we're looking to see if there are more hydrogen ions
are more hydroxide ions. that's really all it is.
now how do we measure the acidity
of a solution or the alkalinity of a solution. we use something that's
called the pH
scale and I'm really hoping that this isn't the first time you're hearing this.
basically the pH scale
measures the concentration of hydrogen ions so we're looking at
are there a lot of hydrogen ions or not. the scale has a range
of zero to fourteen.
let's draw this out into your notebook. I want you to draw this scale
from 0 to 14 and go ahead and label it as I have
on the screen with the acids on the left hand side
which shows that that's where the more hydrogen ions are
and the bases are on the left hand side
right hand side I'm sorry. okay
so let's draw the pH scale into your notebook can i want you to
draw it exaclty as I have shown you here on the screen.
go ahead and number from 0 to 14 and as you label
along the top just pay attention to the fact that as the number gets smaller
that's the side with the acids that means they have more
hydrogen ions. as you go to the right hand side of the scale or as the numbers get
larger
that means there's actually more hydroxide ions, it becomes more of a
basic solution
and 7 right in the middle is considered our neutral solution
for hydrogen ions and hydroxide ions are
exactly the same in that solution. once you have that drawn
I'm going to have you put a couple of different examples of acids and bases
onto your chart. so these are the pH
numbers of different solutions that you probably heard of before.
so let me show you how to do one and then you can do the rest.
so you can see stomach acid has a pH of 2
so on my scale I'm going to go ahead and draw
on the number where pH number 2. I'm going to write stomach acid. you go
ahead and label
the rest. we are done for today that was it.
we're gonna be doing a lab as you are coming into class, doing more about pH
You are going to have a little problem that you're going to have to solve for me.
you're going to have to understand this basic concept of pH
be able to understand the difference between acid and base.
at this point though we're not ready for you to do the questions and now I know
so please don't do this in your notebook yet.
all i'm looking for are those few notes that you just finished taking