In this lab, you will have the opportunity to become familiar with
hands-on measurements, some error analysis, and build upon the concepts
covered in this week’s lectures: ratios, volume, and surface area.
Equipment required for this week’s lab
Week 1: General
Measurements and Ratios
If you have popped a batch
of popcorn, you know that a given batch of kernels might pop into big and
fluffy popcorn. But another batch might not be big and fluffy and some of the
kernels might not pop. Popcorn pops because each kernel contains moisture that
vaporizes into steam, expanding rapidly and causing the kernel to explode, or
pop. Here are some questions you might want to consider investigating to find
out more about popcorn: Does the ratio of water to kernel mass influence the
final fluffy size of popped corn? (Hint: Measure mass of kernel before and
after popping). Is there an optimum ratio of water to kernel mass for making
bigger popped kernels? Is the size of the popped kernels influenced by how
rapidly or how slowly you heat the kernels? Can you influence the size of
popped kernels by drying or adding moisture to the unpopped kernels? Is a
different ratio of moisture to kernel mass better for use in a microwave than
in a conventional corn popper? Perhaps you can think of more questions about popcorn.
The purpose of this introductory laboratory
exercise is to investigate how measurement data are simplified in order to
generalize and identify trends in the data. Data concerning two quantities will
be compared as a ratio, which is generally defined as a relationship
between numbers or quantities. A ratio is usually simplified by dividing one
number by another.
Part A: Circles and
three different sizes of cups, containers, or beakers with circular bases.
Trace around the bottoms to make three large but different-sized circles on a
blank sheet of paper.
the diameter on each circle by drawing a straight line across the center.
Measure each diameter in mm and record the measurements in Data Table 1.1.
Repeat this procedure for each circle for a total of three trials.
the circumference of each object by carefully positioning a length of string
around the object’s base, then grasping the place where the string ends meet.
Measure the length in mm and record the measurements for each circle in Data
Table 1.1. Repeat the procedure for each circle for a total of three trials.
Find the ratio of the circumference of each circle to its diameter. Record the
ratio for each trial in Data Table 1.1.
4. The ratio of
the circumference of a circle to its diameter is known as pi (symbol?), which has a value of 3.14… (the periods mean
many decimal places). Average all the values of ? in Data Table 1.1 and
calculate the experimental error.
Part B: Area and
one cube from the supply of same-sized cubes in the laboratory. Note that a
cube has six sides, or six units of surface area. The side of a cube is also
called a face, so each cube has six identical faces with the same area.
The overall surface area of a cube can be found by measuring the length and width
of one face (which should have the same value) and then multiplying
(length)(width)(number of faces). Use a metric ruler to measure the cube, then
calculate the overall surface area and record your finding for this small cube
in Data Table 1.2.
volume of a cube can be found by multiplying the (length)(width)(height).
Measure and calculate the volume of the cube and record your finding for this
small cube in Data Table 1.2.
3. Calculate the
ratio of surface area to volume and record it in Data Table 1.2.
a medium-sized cube from eight of the small cubes stacked into one solid cube.
Find and record (a) the overall surface area, (b) the volume, and (c) the
overall surface area to volume ratio, and record them in Data Table 1.2.
Build a large cube from 27 of the
small cubes stacked into one solid cube. Again, find and record the overall
surface area, volume, and overall surface area to volume ratio and record your
findings in Data Table 1.2.
a pattern, or generalization, concerning the volume of a cube and its surface
area to volume ratio. For example, as the volume of a cube increases, what
happens to the surface area to volume ratio? How do these two quantities change
together for larger and larger cubes?
Part C: Mass and
at least three straight-sided, rectangular containers. Measure the length,
width, and height insidethe container (you do not want the container
material included in the volume). Record thesemeasurements in Data
Table 1.3, in rows 1, 2, and 3. Calculate and record the volume of each
container in row 4 of the data table.
and record the mass of each container in row 5 of the data table. Measure and
record the mass of each container when “level full” of tap water. Record each
mass in row 6 of the data table. Calculate and record the mass of the water in
each container (mass of container plus water minus mass of empty container, or
row 6 minus row 5 for each container). Record the mass of the water in row 7 of
the data table.
the volume here
a graduated cylinder to measure the volume of water in each of the three
containers. Be sure to get all the water into the graduated cylinder.
Record the water volume of each container in milliliters (mL) in row 8 of the
the ratio of cubic centimeters (cm3)
to mL for each container by dividing the volume in cubic centimeters (row 4
data) by the volume in milliliters (row 8 data). Record your findings in the
Calculate the ratio of mass per
unit volume for each container by dividing the mass in grams (row 7 data) by
the volume in milliliters (row 8 data). Record your results in the data table.
a graph of the mass in grams (row 7 data) and the volume in milliliters (row 8
data) to picture the mass per unit volume ratio found in step 5. Put the volume
on the x-axis (horizontal axis) and the mass on the y-axis (the
vertical axis). The mass and volume data from each container will be a data
point, so there will be a total of three data points.
a straight line on your graph that is as close as possible to the three data
points and the origin (0, 0) as a fourth point. If you wonder why (0, 0) is
also a data point, ask yourself about the mass of a zero volume of water!
Calculate the slope of your graph. The slope of a line is the change in rise
divided by the change in run.
9. Calculate your
experimental error. Use 1.0 g/mL (grams per milliliter) as the accepted value.
Density is defined as mass per
unit volume, or mass/volume. The slope of a straight line is also a ratio,
defined as the ratio of the change in the y-value per the change in the x-value.
Discuss why the volume data was placed on the x-axis and mass on the y-axis
and not vice versa.
Was the purpose of this lab
accomplished? Why or why not? (Your answer to this question should show
thoughtful analysis and careful, thorough thinking.)
1. What is a ratio?
Give several examples of ratios in everyday use.
2. How is the value of? obtained? Why does?not have units?
what happens to the surface area to volume ratio for larger and larger cubes.
Predict if this pattern would also be observed for other geometric shapes such
as a sphere. Explain the reasoning behind your prediction.
4. Why does
crushed ice melt faster than the same amount of ice in a single block?
contains more potato skins: 10 pounds of small potatoes or 10 pounds of large
potatoes? Explain the reasoning behind your answer in terms of this laboratory
6. Using your own words, explain the meaning of
the slope of a straight-line graph. What does it tell you about the two graphed
why a slope of mass/volume of a particular substance also identifies the
density of that substance.
An aluminum block that is 1 m× 2 m× 3 m has a mass of 1.62× 104
kilograms (kg). The following problems concern this aluminum block:
l. What is the
volume of the block in cubic meters (m3)?
2. What are the
dimensions of the block in centimeters (cm)?
3. Make a sketch
of the aluminum block and show the area of each face in square centimeters (cm2).
4. What is the
volume of the block expressed in cubic centimeters (cm3)?
5. What is the
mass of the block expressed in grams (g)?
What is the ratio of mass (g) to
volume (cm3) for
what topic would you look in the index of a reference book to check your answer
to question 6? Explain.