Density Lab
Materials:
One 25, one 50, and one 100ml graduated cylinder
Tray with samples of: aluminum, steel, lead, zinc, copper, brass and at least pennies
Beaker of salt water
Procedural information:
 When measuring mass of a metal sample, make sure the metal is dry before massing
o Make sure grams (g) are the expressed units on the balance
o Put a piece of paper on your balance and hit “on/zero” or “tare” button
o Place the dry metal on the balance and record the mass.
 When measuring the volume in the graduated cylinder estimate to the nearest 1/10th of the
smallest division shown.
o Choose the smallest graduated cylinder the object will slide easily into (be careful the
graduated cylinders are wider at the top than the bottom, so what barely fits in the
top will likely get stuck before reaching the bottom of the cylinder).
o Put some water in the graduated cylinder flick the cylinder to get rid of trapped air
bubbles (you can usually start with about 15 ml in the 25ml cylinder, 20 ml in the 50ml
cylinder, and 30ml in the 100 ml cylinder)
o Record the initial volume of the water.
o Tilt the graduated cylinder towards the side so that the metal can slide down the side
into the water.
 If you drop the sample in, it can splash out water making your data inaccurate,
and damage the graduated cylinder.
o Carefully place the metal sample in the water, by letting it slide down the side.
o Flick the cylinder again to get rid of trapped air bubbles, record the final volume.
 Use the following density equation to solve for the density:
Density = mass
m
volume
d V
Measuring Density
Per.:
Name:
Date:
Predictions and Pre-lab: For all explanations, write in complete sentences.
For questions 1-2, you are to predict, without looking up actual values, densities, etc.
1.
Make an educated guess which of the following substances do you think modern
pennies are primarily made out of: zinc, copper, brass, aluminum, steel, lead, or water, or
salt water:
any metal; Why do you think that?
Your reasoning
2.
Make an educated guess and rank what you think the densities of zinc, copper, brass,
aluminum, steel, lead, water, and salt water will be the starting at the lowest density (1) and
going to the highest density (8).
1 (least):
5:
3.
4.
water or salt water; 2:
; 6:
; 3:
; 7:
; 4:
; 8 (most): metal
(not Al)
g/ml
What is/are the standard unit(s) of density in the metric system?
If an object’s volume stays about the same, but its mass increases (like what happens when
dissolving a substance in water), what will happen to the object’s density? Explain
Density will increase because there is more stuff in
the same volume (or the numerator is getting bigger
while the denominator stays the same).
5.
Most materials expand in volume while they are heated, and contract in volume while they
are cooled (but they keep the same mass). What happens to most materials’ densities as
they are heated? What about cooled? Explain.
The mass stays the same in both cases (same
numerator). As the object is heated, the volume
increases, meaning there is the same amount of stuff
in a larger volume, (same numerator, bigger
denominator) so density decreases; as the object is
cooled, the volume decreases, meaning there is the
same amount of stuff in less volume (same numerator
smaller denominator), so density increases
6.
Metals typically sink in water, what does that mean about a metal’s density compared to
water’s density? Explain
;
Because objects float on fluids that are denser than the
objects are, but sink in fluids that are less dense, the
metal’s density must be more than the water’s density.
End of page 1:
7.
What happens to the volume of water as it freezes? What does that mean about what
happens to water’s density as it freezes? Why? Use that to explain why ice floats in water.
The volume of water increases as it freezes, that
means the density decreases because there is the same
amount of stuff in more space (or same numerator
with bigger denominator). Since objects float on
fluids which are denser than the object is, ice floats on
water because it is less dense than the water.
8.
Liquid water does the expansion and contraction as described in pre-lab question 5,
however water is actually most dense at 4ºC (below 4°C, the water starts to expand). Given
this, what happens to the water at the surface of a lake when it cools to 4ºC? Given that,
why do large bodies of fresh water (like the Great Lakes), almost never freeze over even
when it’s well below freezing outside for months?
The 4°C water sinks to the bottom. In order to freeze
over, the water has to drop below 4°C, but the 4°C
keeps sinking, so the entire water column from the
bottom of the lake to the surface has to be cooled to
4°C before the top layer can be cooled enough to
freeze.
9.
A way of describing where people live is using “population density” or number of people
living in a certain area. How is this similar to density in the science?
It’s very similar, density in science in how much stuff
there is in a certain volume, so instead of stuff per
volume the population density is people per area (hard
to do volume without stacking people).
10.
By adding dissolved substances to water, the mass of the “water” increases but the volume
stays about the same (essentially some of the dissolved substances fit between the water
molecules). Using this information, what happens to the water’s density? Use that info to
explain why people float better in very salty bodies of water, like the Great Salt Lake or the
Dead Sea than they do in the fresh water bodies of water.
The mass increases so there is more stuff in the same
volume, so the density increases (there is a greater
numerator for the same denominator). Because there
is more density in very salty lakes, people float better
because they are much less dense than the liquid
surrounding them.
Data:
Find the mass (to the precision of 1/100th of a gram), volume (to the nearest 1/10th of a ml: so, if
it’s exactly 13 ml, write it as 13.0ml), and density of each of the following substances:
Density (show work and express to
Sample
Mass
Volume (show work!)
correct significant figures!)
Zinc
Aluminum
Brass
Copper
Steel
Lead
29.16g
17.53g
53.95g
56.94g
53.95g
112.27g
42.4-38.2=4.2ml
32.1-25.8=6.3ml
76.0-69.6=6.4ml
63.1-56.8=6.3ml
36.3-28.2=8.1ml
63.1-53.7=9.4ml
29.16/4.2=6.9 g/ml
17.53/6.3=2.7 g/ml
53.95/6.4=8.4 g/ml
56.94/6.3=9.0 g/ml
62.19/8.1=7.7 g/ml
112.27/9.4=12 g/ml
m (show work):
Water
95.85 – 41.19 54.9ml
= 54.66g
54.66/54.9=0.996 g/ml
m (show work):
Salt Water
80.26 – 24.37 49.2 ml
= 55.89
55.89 / 49.2 = 1.14 g/ml
Find the mass, volume and density of (again measure to the correct level of precision, use the 50ml
graduated cylinder and start with about 20 ml):
Pennies
Mass
Volume (show work!)
Density (show work and express to
correct significant figures!)
5 pennies
10 pennies
20 pennies
40 pennies
80 pennies
12.54
25.05
52.51
102.63
202.70
1.7
3.4
7.1
14.4
28.5
12.54/1.7 = 7.4g/ml
25.05/3.4 = 7.4 g/ml
52.51/7.1 = 7.4 g/ml
102.63/14.4 = 7.13 g/ml
202.70/28.5 = 7.11 g/ml
Conclusions:
1.
Which measurement likely has more error to it, the mass measurement or the volume
measurement? Why is that? (Hint, think about where we have to estimate and in which
case and in which case(s) do we have more significant figures?)
The volume measurement because that has more
estimation to it, especially for smaller volumes.
2.
Which density calculation is likely the most accurate (10, 20, 40, or 80 pennies)? Why is
that?
The 80 penny data, because a small error in volume
measurement leads to a lower error (0.1 ml out of 28.5
isn’t as big of a deal as 0.1ml out of 1.7ml)
3.
Look at the masses of the pennies each time you doubled the number of pennies (from 5 to
10, 10 to 20, 20 to 40, and 40 to 80), divide the masses of the larger amount of pennies by
the smaller amount of pennies to see a relationship (show work):
5 to 10
10 to 20
20 to 40
40 to 80
Approximately what happened to the masses each time? (Did the masses half, double,
quadruple, stay about the same, or was there no relationship?)
make sense?
doubled Why does that
Since there is twice as many pennies, the mass should
be about twice as much
4.
Look at the volumes of the pennies each time you doubled the number of pennies (from 5
to 10, 10 to 20, 20 to 40, and 40 to 80), divide the masses of the larger amount of pennies
by the smaller amount of pennies to see a relationship (show work):
5 to 10
10 to 20
20 to 40
40 to 80
Approximately what happened to the volume each time? (Did the volume half, double,
quadruple, stay about the same, or was there no relationship?)
make sense?
doubled Why does that
Each penny has about the same volume, so when the
number of pennies is doubled, the volume doubles
5.
Look at the densities of the pennies each time you doubled the number of pennies (from 5
to 10, 10 to 20, 20 to 40, and 40 to 80), divide the masses of the larger amount of pennies
by the smaller amount of pennies to see a relationship (show work):
5 to 10
10 to 20
20 to 40
40 to 80
Approximately what happened to the density each time? (Did the density half, double,
quadruple, stay about the same, or was there no relationship?)
does that make sense?
stayed same Why
Each penny has the same composition, so it should
have the same density. (We have twice as much stuff,
packed into twice as much volume, so the particles are
equally densely packed)
6.
Look at the density values from the data and results section. Compare those densities with
the density of the pennies you said would be most accurate. Based on these observations,
zinc
which of these materials are pennies primarily made out of?
Why are you able to
make this conclusion? How does this compare to your prediction in number 1? (write in
complete sentences)
The closest metal in density to the pennies is zinc, so
the pennies must be primarily made of zinc.
Compare to your prediction
7.
Another coin from a different country has a mass of 13.1g and a volume of 4.7ml. What is
this coin likely made of? Explain.
d = 13.1g / 4.7ml = 2.79g/ml, so the coin is likely
mostly aluminum because that is the closest density.
11.
Rank the zinc, aluminum, brass, copper, steel, lead, water, and salt water starting at the
lowest density (1) and going to the highest density (8).
1 (least):
5:
water
steel
; 2:
salt water
; 3:
aluminum; 4: zinc ;
; 6:
brass
; 7:
copper
; 8 (most):
lead
How does this compare to your prediction in pre-lab question 2?
Compare to your prediction
12.
Based on your density values, why are airplanes often constructed out of aluminum instead
of another metal like steel or copper, make sure to include ideas of density in your
explanation?
Since aluminum has the lowest densities of the metals,
the mass is the least for the same volume, meaning
airplanes are lighter and can thus fly easier.
13.
Based on your density values, why is lead often used as “sinkers” in fishing, make sure to
include ideas of density in your explanation?
Since lead has the highest densities of the metals, the
mass is the most for the same volume, meaning the
sinkers have more mass and are able to pull down the
lines better.
14.
Any constant ratio can be written as a conversion factor (if an object is constantly moving
at 10m/s, we can say 10m = 1s for that object, because there is 10m travelled for every 1s of
time). Given this, write what you determined to be the most accurate density value as three
conversion factors (#pennies = mass, #pennies = vol; and mass = vol):
80 pennies = 202.70g;
80 pennies = 28.5g; 7.11g = 1ml
15.
Using your most accurate density value, calculate the volume of 155g of pennies (show
work using the conversion factor method and the conversion factor from concl. #14):
|
16.
Using your most accurate density value, calculate the mass of 15 ml of pennies (show work
using the conversion factor method and the conversion factor from concl. #14):
|
17.
Using the data you found in what you determined to be the most accurate density data:
a. Find the vol. and mass of a single penny. Show your work using grid conversion factor
method, using conversion factors from concl. #14 (start with 1 penny and go to g or ml).
|
|
b. Calculate how many pennies could fill a 120.0 m3 room (1m3 = 1,000,000cm3; 1 ml = 1
cm3), assuming there was no space between the pennies. Show your work using the
grid conversion factor method, using conversion factors from concl. #14.
|
|
|
c. How much mass would the number of pennies in part b have? Show your work using
the grid conversion factor method, using conversion factors from concl. #14
|
18.
Make two different graphs of the appropriate type(s) to match the descriptions below.
Include all the qualities of a good graph.
a. graph that compares the density of
b. shows how the mass of the pennies
the materials to each other
changed as the volume of the
pennies changed as you went from 5
 10  20  40  80 pennies.
Put mass on the y-axis and volume
on the x-axis.
Density of different materials
Mass and volume of pennies
14
250
80 pennies
200
10
mass of pennies (g)
Density (g/ml)
12
8
6
4
2
150
40 pennies
100
20 pennies
50
0
10 pennies
5 pennies
0
0
Material
19.
5
10
15
20
25
volume of pennies (ml)
What kind of relationship does the graph in conclusion 18b show? If you were to find the
slope of the relationship shown in conclusion 18b, what info would that tell you and why?
How does that help explain the shape of the graph in 18b? Explain
The relationship is fairly linear. Slope is rise over run,
or mass over volume for the pennies. Mass over
volume is density, so the slope is the density of the
pennies. Because the density is constant, the slope
must be constant.
20.
What are some sources of error in this experiment? (write in complete sentences)
At least 2 sources of error
Hard to estimate to the nearest 1/10th of a ml.
Mass not zeroed properly
Water splashed out of cylinder when adding materials
30