**8 ^{th} Grade Science Professor Shai**

**Density of Liquids Experiment**

**Section 3.9 Page 51**

You
are going to
measure the density of an odorless, colorless liquid.
Half the class will have one liquid called Mystery A, and the
other will have Mystery B. Dont taste
the liquid, yuck!

To
measure the
density of a liquid you do the same thing you would for a solid. Mass the fluid, find its volume, and divide
mass by volume.

To
mass the fluid,
weigh it in a container, pour it out, weigh the empty container, and
subtract
the mass of the empty container from the full container.

To
find the volume
of the fluid, you simply measure it very carefully in a graduated
cylinder.

Question: Should you first find the volume of the
liquid or mass the liquid?

Answer: The two choices are:

1. Weigh fluid in
beaker. Pour out to graduated cylinder, and weigh again.
The mass of the fluid is the difference of the two weighings. The
volume is the measurement you see in the graduated cylinder. Note
that this method does not include the remants of fluid that cling to
the beaker in the massing. The remants are also not oncluded in
the volume measurement.

2. Pour the fluid into a
graduated cylinder and read its volume. Then weigh the graduted
cylinder. Then pour the fluid out, and weigh again. The
weight of the fluid is the difference between the two weighings.
Note that this method, after pouring the fluid from the graduated
cylinder, includes the remnants of fluid in the volume reading, but not
in the mass calculation.

And the right way to do it is (1). When you find the mass or
measure the volume of the fluid, you will not include the fluid that
clings to the empty container from which you poured it.
Therefore, you should mass first as in choice one above. In choice 1, after you mass and then pour to measure
volume, the remnants of fluid left in the beaker do not get included in
the mass or the volume calculation. Getting included in
neither is fair. However, if you find the volume first, and then
mass, the remnants of fluid in the graduated cylinder volume *would*
be included in the volume measurement but not in the mass measurement.

Report
the density
of your liquid on the board.

Are
the two
liquids the same?

When
you mix salt
with water, the total volume decreases but the mass remains the same. What should happen to the density?

8^{th} Grade Science Professor Shai

Density of
Liquids Work Sheet

** **

**Fluid
1 Density Analysis**

** **

Density of
Actual Fluid (C / D)
E. _________

**Fluid
2 Density Analysis**

** **

Density of
Actual Fluid (C / D)
E. _________

Report your
group result on the histogram on the
board.

Do problem 15
in your text.