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CLAIRE HALLORAN: Today, we're going
to be doing goody bag 1, atoms and reactions.
Our objectives today are to identify material
based on its properties, observe a simple chemical reaction,
and identify the limiting reagent,
and estimate the number of atoms in a real object.
To do this goody bag, you'll need vinegar, a plastic cup,
a ruler, metal samples of aluminum, copper, iron,
magnesium, and tin, but if you can only
get copper and magnesium, it will work, and a pipette.
Some conceptual questions to think about
while you're doing this goody bag are,
how can we tell different metals apart,
and how can we count atoms that are too small to see?
First, we have five samples of metal
that we would like to identify using their properties.
The easiest to identify is copper by its orange-ish color.
Next, we're going to try to find out
which sample is iron by testing how easy they are to bend.
Iron will be the most difficult to bend.
So this sample bends very easily just with my fingers,
so it must not be iron.
This sample is very difficult. I can hardly
get it to bend at all with my fingers,
and this sample also bends fairly easily just
using my fingers.
So we know that this sample, the hardest to bend, must be iron.
Next, we're going to try to compare the density
of these different metals.
So this metal feels the heaviest and most dense.
This one's feels lighter, and this sample
feels light as well.
So we know that tin is the most dense metal,
so this sample must be tin.
To identify which of these samples is magnesium
and which of them is aluminum, we're
going to test which one of them reacts with vinegar.
So we're going to place each of these samples
on the lid of our plastic cup to make
sure we don't spill any of the vinegar
and use our pipette to put a drop of vinegar
on each of the samples, and the one that reacts
will be magnesium, because we know magnesium reacts
with vinegar watch closely.
It doesn't look like we're getting any reaction
from this metal, so it must be the aluminum
now, let's try the other.
You can see that this material's forming tiny bubbles after we
put the vinegar on it, so it must be magnesium.
Those bubbles are hydrogen gas.
Now, that the bubbling has stopped on our magnesium,
we note that the reaction is over.
There's still plenty of magnesium left,
so this indicates that the acetic acid inside
of the vinegar must be the limiting reagent.
Finally, we want to estimate how many atoms
are in our sample of copper.
To do so, we're going to use a ruler.
Using our ruler, we can measure the width and the height
of this copper sample.
So using the metric side of our ruler,
we align the 0 with the edge of our material
and see that it is about 13 millimeter wide and 25
millimeter long.
Today, we did goody bag 1.
We identified our metal samples based on their material
properties, we observed a simple reaction
and identified the limiting reagent,
and we measured our copper to estimate the number of atoms
in our sample.