Chemistry
Discovery 1-3 Density
A. Mass & Volume
Now that we have tools to measure the size (volume) and the amount of matter (mass) of a
substance, it would be useful to see what relationship exists between these two measurements.
In this discovery, you will measure the mass and volume of samples of two metals: metal A and
metal B. Then, you will graph your data and examine the relationship that exists between mass
and volume.
Metal A
Metal B
Sample #
Mass (g)
Volume (mL)
Mass (g)
Volume (mL)
1
2
3
4
5
6
Input your data into an Excel spreadsheet. Make a xy-scatter plot with both sets of data on the
same graph. You will need to include a legend on this graph. Add the best-fit line (trendline) for
each data set. Include the equation of the line and R2 on your graph. Print your graph.
1. What is the slope (with units) of: A?
B?
2. What does the slope tell us about the two metals? (what does slope mean in this discovery?)
3. How does metal A compare to metal B?
4. In the boxes below, draw a particle drawing comparing a piece of metal A and a piece of
metal B (assume the metal pieces are the same size).
A
B
5. a. How precise is your data? Explain how you know.
b. How could the precision (and accuracy) be improved in this discovery?
B. Density Problem-Solving
1. Study the matter shown in Figure 1. Each dot
represents a particle of matter. [Assume the particles are
uniformly distributed throughout each object, and
particles of the same size have the same mass.]
a. Show the masses, volumes, and densities of A and B
compare by adding the symbol <, >, or = to the
second column.
FIGURE
Figure
1 1
A
A
b. Explain your reasoning for each answer.
Property
Relationship
Mass
A ____ B
Volume
A ____ B
Density
A ____ B
Reasoning
B
B
Chemistry
2. In Figure 4, a graph shows the relationship between mass and volume for two substances, A and B.
FIGURE 4: Mas s and
Volume Relations hips
Two Pan Balance
80
70
A
Subs tance A
B
Mass (g)
60
50
40
30
20
Subs tance B
10
0 10 20 30 40 50 60 70 80
volu me (mL)
a) You have built a simple two-pan balance shown above
to compare the masses of substances A and B.
What would happen to the balance if you put equal
masses of A and B in the two pans? Explain.
Equal volumes of A and B in the two pans? Explain
b) Find the slope of the line for both A and B using correct
units. Show work.
c) If you put 10.0 mL of A in one balance pan, how much mass of B would you need in the other pan to
make it balance? Explain your reasoning.
d) If you put 35.0 mL of B in one balance pan, what volume of A would you need in the other pan to
make it balance? Explain your reasoning.
e)
A liquid has a density of 1.00 g/mL. Sketch the line representing this liquid on the graph in Figure 4.
Which substance(s) will sink when placed in a bucket of this liquid?
Refer to the table of densities at the right to answer the
following questions in #3.
Substance
Aluminum
Titanium
Zinc
Tin
Iron
Nickel
Copper
Silver
Lead
Mercury
Gold
Density
(g/mL)
2.70
4.54
7.13
7.31
7.87
8.90
8.96
10.50
11.35
13.55
19.30
3. a. Sketch a graph of mass vs volume for titanium, copper and mercury.
b. You made some cubes out of each metal in the table that each measures 2.00 cm on every side. (all
except mercury – why can’t you make a cube of mercury?) What is the volume of each cube in
cm3? in mL? Show your thinking.
c. Given the volume above, find the mass of these metal cubes. Show your work for the lead cube.
4. A standard backpack is approximately 30cm x 30cm x 40cm. Suppose you find a hoard of pure gold
while treasure hunting in the wilderness. How much mass would your backpack hold if you filled it with
the gold? Would you be able to carry this gold-filled backpack on your hike? Explain.
Chemistry
C. Dimensional Analysis
Use Dimensional Analysis to make the following conversions. Show your work. Record your answer
with the appropriate number of significant figures.
1. Convert 74 cm to meters.
2. Convert 8.32 x 10-2 kg to grams.
3. Convert 41.0 mL to liters.
4. Convert 9.1 x 10-13 kg to ng.
5. Convert 59.0 kg to mg. Express your answer in scientific notation.
6. Chloroform is a liquid once used for anesthetic. What is the volume of 5.0 g of chloroform? The
density of chloroform is 1.49 g/mL.
7. A sheet of copper has a volume of 0.947 cm3. What is its mass? The density of copper is 8.96 g/mL.
8. How many nickels could you trade for 250 yen? $1 = 150 yen. Change to medical.
9. Your school club sold 600 tickets to a chili supper. The chili recipe for 10 persons requires 2
teaspoons of chili powder.
a. How many teaspoons of chili powder will you need altogether?
b. How many cups of chili powder will you need? Three teaspoons (tsp) equal one tablespoon
(T) and 16 tablespoons equal 1 cup.
10. How many m3 is 4.6 cm3? Express your answer in scientific notation.
D. Density of a Liquid & Gas
In this discovery you will determine and compare the density of a liquid (water) and a gas (carbon
dioxide). As seen in D1-1A, Alka-Seltzer dissolves in water and produces carbon dioxide gas (CO2). The
gas will be collected by water displacement. The reaction test tube is connected to a bottle filled with
water submerged in a bucket.
1. Determine the density of water. Describe how you measured the mass
and volume. Record your measurements in the data table.
2. See diagram at right for the lab set up to collect CO2 gas.
3. Be sure the collection bottle is completely full with H2O & no air bubbles.
4. Do not add the Alka-Seltzer yet. Find and record the combined mass of
½ tablet of Alka-Seltzer and a test tube ¼ -filled with water.
5. Secure the test tube in the clamp. Drop the Alka-Seltzer into the water in
the test tube, and quickly secure the stopper in the test tube. The gas
bubbles should be going into the collection bottle.
6. When the reaction is complete, re-mass the test tube and contents. Record
and determine the mass of carbon dioxide released.
7. Measure the volume of gas in the bottle. Determine a method to do this—
there are two equally good ways to do this. Describe what you did. Include any measurements you
made. Record the volume in the data table below.
Mass (g)
Volume (mL)
Density (g/mL)
Water
AS + water + test tube (before)
AS + water + test tube (after)
Carbon Dioxide Gas
8. Calculate your percent errors. Show your work. The actual density of water at 25°C is 0.999 g/mL. The
accepted value of carbon dioxide gas is 2.0 x 10-3 g/mL.
9. Discuss your accuracy. How could it have been improved?
10. Record your experimental densities for Solid A (from D1-2A), Liquid Water, and Carbon Dioxide Gas.
Then, draw particle diagrams for each state of matter that is consistent with your results.
Solid A
Liquid Water
Carbon Dioxide Gas