OK, so today we are going to explore
Archimedes’ Principle by trying to answer
the question: “If you have floating ice cubes
in a glass of water will the level of
water change when the ice melts?” So, will the
level of water go up or down once the
ice is completely melted? so we're going
to use four different types of ice, or ice
that has slightly different
characteristics in four different ways. And
each one of these identical glasses has
been marked where 250 milliliters of
water will reach. So we can demonstrate
that right here. We have some previously
measured out : 250 milliliters. You can see it
reaches that level on the glass, and when we put it in here, that will be 250 milliliters.
So what we've done is previously
measured the weight of each of the ice
cubes or total of ice cubes that will go
in each class and we are going to add
water back into the glass until it
reaches that level and we're going to
measure the remaining water in the pyrex
cup so that way we can determine how much
water has been added
And we'll use all of this data for our
calculations and we'll try to figure out
if Archimedes was correct. And, we'll try to
answer our question of whether or not
this level of water changes. So, we’ll get the ice from the
freezer
alright so we have our ice from the
freezer and each one of these glasses
was in the freezer previously so
that they're a little bit cooler than
temperature and hopefully the ice doesn’t immediately melt
but we'll put our standard
freezer ice that's been created by the
freezer itself first, and we'll put that into this
glass and pour off some water until it
reaches that level. And it looks like we just need a
touch more
alright so that is our level there and what
we're going to do is put these
back in the freezer so they don't melt.
But, we'll repeat for each one of these
and we’re going to record this level of water and
try to figure out how much we’ve used.
ok so a few details we wrapped our first
cup with saran wrap to help prevent any
sort of evaporation during the
melting process and although the
accuracy on this is only so great we
are using this to pour the water off in
and get the accuracy down
to the five milliliter or maybe two
milliliter plus or minus range maybe
plus or minus 1 and then we have our
three other ice cubes so we'll go
through exactly we have here this is a
spherical ice cube which has iron nails
embedded in to it and previously we weighed
those iron nails before they were made
into the ice cube and these spherical
cubes were created using these silicon
ramekins
this is a plain water ice sphere, and this
one although it's larger, because of the
way it was created has an air pocket on
the inside so this was created using
this setting into one of those ramekins
as the ice froze  and this one has an air pocket in it.
So, this has nails this has air and this is
solid ice
so with each one of those we're going to
start with 250 milliliters adding water
until we get to this level same
processes with the first class will
determine how much water it takes for
you to reach that level
ok so we've moved across the kid
to do some calculations we have some
data to work with and we're going to go
ahead and approach Archimedes principle
from the perspective of melting ice in a
glass
so the first thing we want to talk about
density so we know if we put a few items
into water that air is going to flow
it's going to be above the water ice we
all know ice floats and we all know that
nails are going to sink to the bottom of
the water so knowing that those are the
ingredients were working with we can say
with regards to density the density of
the male's greatest greater than the
density of water just created in the
density guys that's greater than the
density of the air so knowing these
things approaching this we can say that
according to Archimedes principle if we
have an ice cube is going to be
displacing a certain amount of water and
the force supporting our ice cube is
going to be equal to the mass of the
water that's been displaced so let's
draw nice
alright so we have a certain amount of
our ice cube below the water and what we
know is that the mass of that displaced
volume is equal to the force that
supporting this ice cube but will be
also known is that this ice cube is
composed of water itself so witness Ice
Cube's melt the mass is going to be
equal to this it's going to be the same
amount of mass because by definition is
made of the same material so what we can
say is that whatever the density is of
ice compared to the density of water
that's going to be equivalent to the
amount of ice below the volume below
compared to the volume of the entire ice
cube so if we can find out that this is
about plate 92 right then we know that
about eight percent is above but what's
more important is that when this melts
mass of this ice cube is by definition
equal to the mass of the water it will
therefore also have the same volume when
it's melted and volume that's being
displaced so the water will stay at the
same level so let's go ahead and make
table over here
because with four types of ice cubes and
we know that it's our standard freezer
ice and it's a standard spherical ice
the post made of ice water water ice
that is and so we will have a water
level that stays the same so you want to
consider that we have two other Ice
Cube's a sphere with nails spirit with
air so let's actually start by
considering the spirit air let's draw
different diagram will say it's like
that inside is there now what we don't
want to consider is the idea that when
this melts the air is somehow going to
end up below the surface
the only thing that will stay below the
surface of the water is the melted water
ice
so this really isn't even part of our
system but more importantly it's the
same density as the outside air so
there's neutral buoyancy between the air
inside the ice cube and outside the ice
cube if we were to fill this with a more
dense gas or put environment with a less
dense outside perhaps helium then yes
there would be some buoyant force
provided and this would end up
displacing water potentially if it was
more dense or at the end but it's not
going to be the case the areas where our
system you could provide extra force by
pushing the ice down then the volume
might change in the water level will
drop but that's not the case that we
have provided in fact indeed
the water level will stay the same so
finally considering our spiritual ice
with nails embedded what we want to
think about is the volume at the end of
the melting process so for these
considerations
this will only consider these fear with
nails the volume of the melted ice
component that's just is not the nails
is equal to the volume of the water
that's supporting
that ice ok so the same situation here
that people but that's not all we're
dealing with
we also have the volume of the nails so
the volume of the nails here and we want
to compare that to the volume of the
water supporting the nails and we know
that the density of the male's is
greater than the density of the water so
that means that the mass is equal
because that's what our communities
tells us then we can actually save the
volume is less for the nails in the
supporting water so when our ice cube
melts the volume that has been displaced
is greater
in the volume of the total melt all
right what does that tell us that tells
us the water level goes down in the case
with the embedded iron nails so the
final thing we want to consider how do
we do a good job so according to our
communities the mass should equal to the
supporting force and we know that the
mass of water is going to be about one
gram per cubic centimeter and one
centimeter cube is the same as 1
milliliter that's how we measure our his
place call you
so if we compare our data focus then
what we know is that we've got an error
2.08 3.08 433
and 4.4
respectively for the standard freezer
ice spiritualize the nails in the air
now what I would have to come in
is that the air more than likely that
was the most complicated IceCube try to
construct to make sure that it didn't
you have an air pocket
it was the most irregular that's
possibly due to that but otherwise were
actually within the fairly large
expected error range because the water
measurement process wasn't entirely
precise but anyway let's go compare
let's get our water levels indeed stay
the same and did the water levels of the
mail go down pieces of equipment that
were used in those process digital scale
the way the ice wrapped in saran wrap
prevent it from getting shorted out our
levels measured slightly more precise in
the pirate stuff using that and then
results so if we paint over the
spherical shaped ice does more or less
appear to be the same here
ice cube with the area right there about
the same in terms of the nails see we
can pick that that's a wrong route to
evaporate not too much your
consideration short period of time
itself up that settle down and we'll
check out finally with the standard
freezer ice seems to be right about the
same
alright so going back to the one with
anything else I see when we expect much
different seed likes that there seems
two indeed be a difference
right perhaps Archimedes would be proud
so here we are with one final shot
summer our work on the board
let's get a quick look at more data
right want to have a wonderful day
keep doing physics
