LAB 1: Metric Measurement and the Scientific Method
Introduction
Did you know that 16 ounces equals a pound, two pints equals a quart and four quarts
equals a gallon? Or that 12 inches equals a foot, three feet equals a yard, 5280 feet equal a mile?
Or that 2,000 pounds equals a ton? Of course you knew that! But does 2,000 pounds equal a
short ton or a long ton? (A long ton is 2240 pounds!) Did you know that if you owned a square
piece of land, 208.7 feet on each side, you had an acre? You probably had some idea as to what
an acre is. And what is a rod? (16.5 feet) Did you know that four gills equals a pint, a peck
equals two gallons and that a grain equals 0.05 scruples, or 0.002083 ounces, or 0.042
pennyweight, or 0.0166 drams? If you didn’t know some of these, shame on you! Of course, you
all also know that water freezes at 32º F and boils at 212º F. These are all measurements, very
confusing measurements, we commonly use in the system of measurements we in the United
States inherited from the British! When I was a little kid, I remember spending quite a bit of time
memorizing these (and other) units of measurement. What a waste of time!
Development of the Metric System and Its Advantages:
Over two hundred years ago, the French realized this was a very confusing set of
measurements. (They had actually invented most of the weights and measurements we use
today.) The National Assembly of France, in 1790, commissioned the French Academy of
Sciences to come up with a more rational set of weights and measures. Their response was to
invent the SI system, Le Système International d’Unités, commonly called the metric system.
The SI system, with some modifications on the original French design, and by
international agreement, is what all scientists use to determine weights and measures; further,
most of the world uses it in industry, business and everyday life. As of this writing, the United
States has not yet fully converted to the metric system; we still produce autos, for instance, using
SAE (Society of Automotive Engineers) nuts and bolts, while the rest of the world uses metric.
Foreign parts in domestic cars may be in metric. Thus, those of us who do a little car work have
to have two different sets of tools! And this probably decreases the foreign sale of American
autos. And while we’re still driving 60 miles per hour on our highways, the rest of the world is
zipping past us at 97 kilometers per hour!
The advantages of the metric system over what I’ll call the American system of
measurement is it is simple to learn, simple to use for calculations, and unifies all the different
types of measurement: linear, area, volume, mass and temperature. Everything is based on
multiples of 10, using the decimal system. (We have 10 fingers and 10 toes, making counting
with the metric system easy!)
Here are two examples of linear measurement. Which one do you think is easier to learn
and use?
U.S. System
36 inches = 3 feet = 1 yard
Metric System
1000 mm = 100 cm = 1 meter
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
The Basic SI Units:
1. Linear measurement is based on the meter (m). A meter is defined as 1,650,763.73
wavelengths of the orange-red line of the spectrum of 86Kr, in a vacuum, which is
approximately 39.37 inches. There are 100 centimeters (cm) in a meter. A useful conversion
is that 1 inch equals 2.54 cm.
2. Mass is based on the gram (g), which is 1/1000 of a kilogram. One kilogram equals the mass
of the platinum-iridium alloy cylinder kept as a standard by the International Bureau of
Weights and Measures in Paris, or the mass of the duplicate cylinder housed by the National
Bureau of Standards in Washington, D.C. One gram is the mass of one cubic centimeter of
water (cc) at 3.98 ºC, or approximately the mass of one cubic centimeter of water at room
temperature.
3. Volume or capacity is based on the liter (L). One liter, simply, is 1,000 cubic centimeters or
0.2645 gallons.
4. Temperature is based on degrees centigrade or Celcius (ºC). At sea level, water freezes at 0º
C (32º F) and boils at 100º C (212º F); a comfortable room temperature would be about 20º C
(about 68º C).
Table 1.1. Common Divisions of Metric Units.
Prefix
Symbol
Superunits—Make Unit Larger
MegaM
Kilok
Hectoh
Dekada
Subunits—Make Unit Smaller
Decid
Centic
Millim
Micro-
Value
Example
1,000,000 = 106
1,000 = 103
100 = 102
10 = 101
1 megaliter (ML) = 106 L
1 kilogram (kg) = 103 g
1 hectometer (hm) = 102 m
1 dekaliter (daL) = 10 L
0.1 = 10-1
0.01 = 10-2
0.001 = 10-3 =
0.000001 = 10-6
1 decigram (dg) = 0.1 g
1 centimeter (cm) = 10-2 m
1 milliliter (mL) = 10-3 L
1 micrometer ( m) = 10-6 m
Table 1.2. Metric units of length (linear measurement).
UNIT
kilometer
meter
decimeter
centimeter
millimeter
micrometer
nanometer
angstrom
picometer
SYMBOL
km
m
dm
cm
mm
m
nm
Å
pm
RELATIONSHIP
1 km = 103 m
base unit
101 dm = 1 m
102 cm = 1 m
103 mm = 1 m
106 m = 1 m
109 nm = 1 m
1010 Å = 1 m
1012 pm = 1 m
1.2
EXAMPLE
length of 5 city blocks
height of doorknob from floor
diameter of large orange
width of shirt button
thickness of dime
diameter of bacterial cell
thickness of RNA molecule
the atomic radius of carbon is 0.91 Å
Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Table 1.3. Metric units of mass.
UNIT
kilogram
gram
milligram
microgram
nanogram
SYMBOL
kg
g
mg
g
ng
RELATIONSHIP
base unit
1 g = 10-3 kg
103 mg = 1 g
106 g = 1 g
109 ng = 1 m
picogram
pg
1012 pg = 1 m
EXAMPLE
small textbook
dollar bill, 1cc of water
ten grains of salt
article of baking powder
Table 1.3. Metric units of volume.
UNIT
liter
milliliter
cubic centimeter
microliter
nanoliter
SYMBOL
L
mL
cm3 or cc
L
nL
RELATIONSHIP
base unit
103 mL = 1 L
1 cm3 = 1 mL
106 L = 1 L
109 nL = 1 m
picoliter
pL
1012 pL = 1 m
EXAMPLE
quart ~ 1 L
20 drops of water
sugar cube
crystal of table salt
Reading a Measuring Scale (and Significant Figures)
To read a measuring scale, first determine what units you’re dealing with. Units are either
given or assumed. If we can assume that the largest increments below are centimeters, then the
smallest increments are millimeters.
Figure 1.1. A measuring scale.
Note that in reading measuring scales, you report the value that is one smaller than the smallest
increment. The final value is extrapolated; it is an estimation. For instance, in the particular
measuring scale below, if the smallest increment is a centimeter, the arrow would correctly
indicate approximately 1.2 cm. The tenths position is extrapolated. If you guessed 1.3 cm, you
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Figure 1.2. A measuring scale indicating centimeters (enlarged).
would not be wrong because the final digit is extrapolated and your eye might be better than
mine! By the way, how many millimeters would this be? It would be 12 mm (or 13, if you
guessed 1.3 cm). We say that there are two significant figures here because 1.2 cm (or 1.3 cm) is
as accurate as we can possibly get; a reported length of 1.26789 would still only contain two
significant figures because the ―6789‖ are fantasies based on pure imagination, thus not
significant.
Now, what if we have a measurement scale with smaller increments? This would give us
more accuracy and more significant figures. Consider the following scale with arrow ―A‖ in the
same place as the scale above:
Figure 1.3. A measuring scale, in centimeters (smallest divisions are millimeters),
with several measurements indicated (enlarged).
Arrow A is at 1.25 cm. Again, you record the value that is one smaller than the smallest
increment. You can read 1.2 cm clearly, but the hundredths position must be extrapolated
(guessed). There are now three significant figures. The value 1.25 has three digits, thus three
significant figures. Note that the number of significant figures increases with the accuracy of the
measurement device! By the way, if you had guessed 1.24 cm for A, I would have to say that you
might be right because, again, the final figure is extrapolated.
As a check, what values would arrows B and C indicate? (Before you continue reading,
see if you can figure this out!) Well, B is about 2.05 cm and C is about 2.40 cm. If the
measurement is right on the line, the extrapolated digit is 0. What about D? D is 3.00. Note that
the arrow is right on the line indicating both 3 cm and 0 tenths. The extrapolated value here is 0
hundredths because the arrow is right on the tenths increment line!
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Finally, let’s look at the E arrow on the line above. It indicates 0.55. The 0 is because it’s
between the 0 and 1 cm mark, the first 5 is the increment mark and the last 5 is the extrapolation.
How many significant figures here? We only have two.
Note that thermometers and balances are simply different types of measurement scales
and obey these same rules for accurate reading!
Reading a Meniscus
Have you ever noticed that there always seems to be a drop or two of water left in the
bottom of your glass when you’re finished drinking a glass of water? This is because water has
an affinity for glass—it sticks to glass. (This is caused by water hydrogen bonding to glass, a
property of water called adhesion.) So, when you put an aqueous (water based) solution into a
graduated cylinder, the water sticks to the sides, forming a half-moon shape called a meniscus.
Graduated cylinders are calibrated to accurately read at the bottom of the meniscus.
As with any measurement scale, first determine the units. Graduated cylinders are usually
calibrated to read milliliters, mL. So, in the figures below, the graduated cylinder to the left
shows marks for 30 and 40 mL. Notice that there are 10 increments between the 30 and 40.
These increments would be single mL increments.
Figure 1.4. Menisci in Three Graduate Cylinders.
Now, look at the meniscus at the end of arrow A. Arrow A is pointing to the correct place
you would read the meniscus. It reads 35.5 mL, with the .5 being the extrapolated value. There
are 3 significant figures here. As in any measurement scale, if the meniscus is exactly on an
increment line, then the extrapolated digit would be a 0. Look at arrow B. That meniscus reads
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
33.0 mL, with 3 significant figures. What about arrow C? It’s indicating 5.5 mL, with two
significant figures.
Accuracy and Precision
Accuracy is how close to a true value a particular reading is. Precision means the
closeness of a series of measurements of a particular object or phenomenon.
Scientific instruments that have to be calibrated, such as scales, can have horrible
accuracy but great precision or pretty good accuracy but not so good precision. Let’s say we
have two scales, A and B, and an object with a known mass of 10.00 g. We weight the object
three times on each scale. Scale A gives us 10.05 g, 9.87 g and 10.00 g. Scale B gives us 8.00 g,
7.99 g and 8.01 g. Scale A has better accuracy than scale B, but scale B has greater precision
than scale A. The accuracy of a scientific instrument depends on its calibration; the precision of
the instrument depends on the quality of the device!
Precision has a second meaning: the number of digits beyond the decimal in a
measurement. Values with more significant figures are more precise. The measurement device in
Figure 1.2 above yields a value of 1.2 cm whereas the measurement device in Figure 1.3 yields a
value of 1.25 cm. The second value, 1.25 cm, is more precise than the first value of 1.2 cm.
Experimental Error Calculation
Experimental values, also called empirical values, are those you determine through
actual measurement or experimentation. Known values are values that are known to be absolute,
generally determined through advanced measurement techniques and extrapolation, neither of
which we’ll worry about here.
If you are asked how accurate a measurement is, you are being asked to calculate the
experimental error. (Of course, you may also be asked directly what the experimental error is!)
To calculate the experimental error, take the absolute value of the difference between the
experimental value and the known value, divide that by the known value, then multiply that
quantity by 100:
% error =
experimental value – known value
known value
x 100
For instance, if you measured a metal bar with a known length of 17.00 cm as 16.8 cm, the %
error would be calculated as follows:
% error =
% error =
16.8 cm – 17.00 cm
x 100
17.00 cm
– 0.20 cm
x 100
17.00 cm
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
% error =
1.18% error
How accurate was your measurement? You had a 1.18% error.
Measurement numbers are continuous data because the number of digits we report for a
particular measurement increases with the increased accuracy of the instrument used. We saw
this above as the number of significant figures increased from Fig. 1.2 to Fig. 1.3. Data that have
exact numbers, such as the number of students in a room or the number of animals in a
population, are called discrete data.
When multiplying or dividing numbers containing continuous data, we report the answer
to the same number of digits as the continuous data number containing the smallest number of
digits in the original problem. In the example above, 16.8 cm has the smallest number of digits of
the two continuous data numbers in the original problem, so the answer has to have only three
digits!
Some Conversions and Unit Analysis
A few conversions that you should memorize (or already know) are as follows:
1.00 inch = 2.54 cm
2.2 lbs = 1.0 kg
1.0 gal = 3.8 L
Note that all of these conversions are continuous data and can be made more accurate by
using more accurate measuring devices to determine them.
All scientists use a type of mathematical logic called unit analysis, also termed
dimensional analysis. This is a mathematical technique or system that allows you to easily solve
complex mathematical problems.
To solve problems using unit analysis, begin with the number you are given (or have)
then multiply it by as many conversions as necessary to solve the problem, making sure that the
units in the numerator of one conversion cancel the units in the denominator of another
conversion in the same mathematical statement so that the units remaining are the desired units!
(Unit analysis takes a little time to master, so don’t freak out if you don’t get this right away!)
A sample unit analysis problem: How many millimeters are there in 12.00 inches?
12.00 in x 2.54 cm x 10 mm
1.00 in
1 cm
= 305 mm
Note that inches in the beginning, actually the numerator of a fraction of 12.00 in over 1, cancel
out inches in the denominator of the second conversion and centimeters in the numerator of the
second conversion cancels out centimeters in the denominator of the third conversion, leaving
millimeters as the unit of the answer.
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
A second example: How many pounds are there in 5.6 kg?
5.6 kg x
2.2 lbs
= 12 lbs
1.0 kg
Note that the math comes out to be 12.32 lbs. But since we are limited to 2 significant figures,
we have to round the answer to 12.
A Note About Units
Always include units when reporting data or the results of calculations; units matter! For
instance, would you rather be paid $25 per hour for a job or 25¢ per hour for a job? Indeed, units
matter!
The Scientific Method
Scientists try to find the best natural explanations for natural phenomena. They do this by
using the scientific method. The scientific method is a systematic way of studying nature using
observations and experiments. Using the scientific method, the scientist 1) makes observations of
the natural world using the senses (smell, sight, hearing, taste and touch), 2) proposes a
hypothesis as the best explanation for the natural phenomenon in question, 3) then designs and
runs an experiment to test the hypothesis that has as one possible outcome the falsification of the
hypothesis.
Observations of the natural world oftentimes depend on the use of scientific instruments
to collect data. If you measure the length of an object with a ruler, the ruler is the instrument.
Microscopes, thermometers and scales are other examples of instruments used in the science of
biology. An example of an observation to illustrate how the scientific method works: When we
go to the rocky intertidal at the seashore, we notice that mussels (Mytilus) live in a narrow zone
that is only submerged by the tides once or twice a day. We also notice that starfish (Pisaster
ochraceus) live only up to but not in the mussel zone. Occasionally, we do see a mussel or two
deep between rocks. These are all scientific observations; these are all scientific facts.
The hypothesis is the best explanation the scientist can propose explaining the
observations he or she initially made. Besides being the best explanation for a natural
phenomenon, a good hypothesis must be falsifiable and must be able to predict future
occurrences of the same natural phenomenon. Back to the mussels and starfish, we might ask
ourselves why mussels generally don’t live deeper within the intertidal? There are other
questions we might also ask, such as why starfish aren’t found commonly up in the mussel zone,
but let’s focus on the mussels! A hypothesis might be: Starfish inhibit the growth of mussels.
The experiment designed to test the hypothesis must have as one possible outcome the
falsification of the hypothesis, and may simply be a further series of systematic observations or
may involve experimental manipulation. To test the hypothesis that starfish inhibit the growth of
mussels, we would use some experimental manipulation. This would involve securing a sample
of living mussels down lower in the intertidal where starfish can get at them. This is what we call
the experimental treatment. In experiments involving manipulation, we need to compare this to
a control treatment. For the control treatment, we move some more mussels down to the same
level as the first group of mussels, only place them within cages that exclude the starfish. The
independent variable is what we change in the experiment, in this case, the ability of starfish to
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
get at the mussels. The dependent variable is what we expect to change as a result of the
independent variable, in this case, the presence or absence of living mussels.
We run the experiment. In the experimental treatment, the mussel shells that we
transplanted and secured lower within the intertidal are empty (dead). Within the starfish-proof
cages, the control treatment, the transplanted mussels are still alive. If the mussels within the
cages (control treatment) were also dead, this would have disproved or falsified our hypothesis.
As it so happens, the results of our experiment support our hypothesis. An appropriate question
now would be, did our experiment prove our hypothesis? The answer is NO! Absolutely not! We
have evidence supporting our hypothesis, but we would, in fact, have to run the experiment an
infinite number of times to absolutely prove the hypothesis. This we cannot do. So, we state that
the results of our experiment support our hypothesis, not that they prove our hypothesis!
So, is the above hypothesis a good one? Well, it appears to be the best explanation for the
natural phenomenon in question and it was falsifiable, meaning that the experiment we designed
could have disproved it! Finally, it can (and does) predict future events related to this natural
phenomenon. If we are fortunate enough to obtain research funding to travel to many rocky
intertidal locations throughout the world that have mussels and starfish, we observe the same
bands of mussels and the same starfish living a bit deeper within the intertidal, although different
species of both; our hypothesis and experiment works the same way in these other locations as
well!
A theory is a unified collection of hypothesis that have been tested without falsification;
theories unite several hypotheses under a single explanation.
A principle or law is a theory that has been tested without falsification so many times
that scientists tentatively accept it as scientific fact, with the understanding of the possibility that
at some time it might be falsified, however unlikely.
Laboratory Objectives
After mastery of this laboratory, including doing the assigned readings and required
laboratory work, the student should be able to:
1. Know the common metric units of length, mass and volume (kilometer, meter, centimeter,
millimeter, micrometer, kilogram, gram, milligram, liter, milliliter) and be able to convert
between them using unit analysis.
2. Read a metric linear scale, graduated cylinder, mass scale and thermometer with the highest
possible precision, including units in the answer.
3. Correctly demonstrate the process of zeroing a scale.
4. Define meniscus.
5. Define accuracy and precision.
6. What determines the accuracy and precision of scientific devices?
7. Differentiate between continuous and discrete data, and know how they are used in the
determination of significant figures in mathematical calculations.
8. Define experimental, empirical and known values.
9. Be able to calculate experimental error.
10. Memorize conversions between the U.S. and metric systems of measurement for linear, mass
and volume measurements and be able to do simple conversions, using unit analysis.
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
11. State what a scientific fact is.
12. State the three components of a good hypothesis.
13. Briefly describe the scientific method.
14. If given a description of an experiment, identify the experimental treatment, control
treatment, independent variable and dependent variable.
15. Be able to propose a viable hypothesis and test it.
16. Explain the difference between a hypothesis, theory and principle.
Materials and Methods
~Make sure you read the lab over and complete the prelab before coming to class!
Linear Measurement: The Diagonal of a Card
1. Obtain an index card and a ruler. In inches, measure the diagonal distance as precisely as
possible and record (with units!) on your lab report sheet to within 1/16 of an inch then convert
to decimals to the hundredth place and add to the whole number. To do this, simply divide the
numerator by the denominator. For instance, 2 8/16 = 2.50, 1 3/16 = 1.19, etc.
2. Next, measure the diagonal distance in centimeters as precisely as your measuring device allows
(to the hundredths place). Record this as well (with units!) on your lab report sheet.
Mass
1. Obtain a 10 mL graduated cylinder and beaker with approximately 3 to 7 mL of tap water in it,
and go to one of the electronic balances set up for your use.
2. Turn the electronic balance on. It should read zero. Place the 10 mL graduated cylinder on it and
record its weight on the results page, with units!
3. Remove the graduated cylinder from the scale. Pour the approximately 3 to 7 mL of tap water
into it (the exact amount does NOT matter) and put it back on the scale. Record the new weight
(graduated cylinder + water) and record (with units) in your lab report.
4. DO NOT EMPTY YOUR GRADUATED CYLINDER! You’re going to read the volume of the
water next!
Volume
1. Remove the graduated cylinder from the scale and read and record the volume as precisely as
possible (with units!) on your lab report page. Make sure you’re looking straight on at the
meniscus and are reading the BOTTOM of the meniscus. Placing the graduated cylinder in front
of a solid black piece of paper or object may help you visualize the meniscus. BEFORE moving
on, have your instructor check the reading and initial your results page!
2. Pour the waste distilled water down the sink.
3. Next, obtain a 100 mL graduated cylinder and fill it from 1/3 to 2/3 full of distilled water—the
exact amount does not matter! Read the value as precisely as possible and record this value.
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
BEFORE you dispose of the water, have your instructor check the reading and initial the value
you wrote down on your lab report page. Dispose of the water down the sink.
Temperature
Lab safety advisory: Biohazard! Thermometers may contain mercury, which is toxic. If
you break a thermometer, notify your instructor immediately for appropriate cleanup.
1. On display in the lab, there should be a ring stand suspending a thermometer in some roomtemperature water. Observe and record the temperature as accurately as possible (with units) in
your lab report. BEFORE moving on have your instructor verify the reading and initial your lab
report page! (The purpose of this is to make sure YOU can read thermometers accurately!)
2. Also on display in the lab, there should be a ring stand suspending a thermometer in some
boiling water atop a hotplate. If the water is not boiling, make sure the beaker is at least ½ full of
water and that the thermometer is suspended in the water but NOT touching the sides of the
beaker! Turn the hot plate on high.
3. When the water is boiling vigorously, observe and record the temperature as accurately as
possible (with units) in your lab report. BEFORE moving on, have your instructor verify the
reading and initial your lab report page.
4. Now, obtain a 250 mL beaker full of crushed ice. Hold or suspend the thermometer in the middle
of the ice for at least five minutes without touching the sides of the beaker. Then, with the
thermometer in the ice, read the temperature as precisely as possible (with units). (Don’t take the
thermometer out of the ice to read it!) Record the measurement on your lab report page then have
your instructor verify and reading and initial your lab report page.
5. Finally, with the thermometer still in the crushed ice, have your lab partner sprinkle about 5 mL
of sodium chloride onto the ice. Gently stir the ice with the thermometer. Wait at least five
minutes, then record the new temperature as precisely as possible (with units); have your
instructor verify your reading and initial your lab report.
6. Pour the ice and sodium chloride down the drain with running water, rinse the 250 mL beaker
and thermometer well with tap water, then rinse three times with distilled water. Dry both with
paper towels. (Unless instructed otherwise in lab.)
The Scientific Method: Ht/W Ratio of a Gastropod Shell
1. We should have in the lab a collection of gastropod shells for you to work with. You and your
lab partner should randomly select 30 shells, or a set of 30 shells will be provided to you. You
will also need a metric ruler for this experiment.
2. Randomly select one of the gastropod shells. Note that gastropod shells have an aperture, the
opening into the shell through which the living animal can extend. Measure the height of the
shell, in millimeters, to the nearest tenth millimeter; remember, the decimal immediately smaller
than the smallest increment is the extrapolated value, which would be the tenth place here. Note
that gastropod shells have an aperture, the opening into the shell through which the living animal
can extend. Measure the width of the gastropod across the widest point, at the aperture opening,
in millimeters, to the nearest tenth. Enter the height and width in the data table for snail number
one. Divide the height into width to obtain the height/width ratio; record this number on your
report sheet.
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
3. The height/width ratio is one of many parameters we use to determine species of certain types of
gastropods. As such, do you think the height/width ratio for the collection of shells you were
presented with will vary or be relatively consistent within the collection of shells? Let’s construct
a hypothesis based on our preliminary observation: The height/width ratio of [gastropod species]
is [use the height/width ratio you calculated]. Record this hypothesis on your lab report sheet.
4. Now, measure as accurately as possible the height and width of each of your gastropod shells.
Record these data on your lab report sheet.
5. Calculate the height/width ratio for each of the shells and record these data.
6. Calculate the mean value (average) for the total height/width ratios and record.
7. Does the mean value support or cause you to reject your hypothesis? Explain in the discussion
part of your lab report.
Make sure you cleanup your work station, clean all equipment you used
and put it back, and help in general to keep the lab clean and in order!
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Biol 160
Lab 1: Metric Measurement
and the Scientific Method
Prelab
(5 points)
Name: ___________________________________
Date: ________________ Lab Section: ________
~Complete this prelab before coming to lab; it is due at the beginning of lab!
1. Complete the following table:
1 km = __________m
__________ mm = 1 cm
__________ mL = 1 L
10 _________ = 1 m
1 mm = __________ m
1000 L = __________ mL
1 m = _________ cm
__________ g = 1 kg
100 cm = __________ m
1.00 inches = _________ cm
__________ lbs = 1.0 kg
1.0 gallons = __________ L
2. Using unit analysis, calculate the number of millimeters in 4.89 inches. Show the unit analysis
equation that is used to solve this problem!
3. Using unit analysis, calculate the number of pounds in 45.79 g. Show the unit analysis equation
necessary to solve this problem!
4. Using unit analysis, calculate the number of gallons in 250 mL. Show the unit analysis equation
necessary to solve this problem!
5. In your own words, define meniscus.
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
6. What is the difference between continuous and discrete data?
7. State the three components of a good hypothesis!
8. Define theory, in your own words!
9. Define scientific principle or law, in your own words!
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Biol 160
Lab 1: Metric Measurement
and the Scientific Method
Lab Report
(20 points)
Name: ___________________________________
Date: ________________ Lab Section: ________
Linear Measurement: The Diagonal of an Index Card
Results
1.
Diagonal Length of Index Card
Inches
Centimeters
Analysis
2. Divide the diagonal distance of your index card in centimeters by the diagonal distance in inches.
This is the experimental value of the number of centimeters per inch.
3. Calculate the experimental error of the value above, given that the known value is 2.54 cm per
1.00 inch!
Discussion
4. How close was your experimental value for the number of centimeters per inch to the known
value? (―Close‖ or ―not close‖ have no meaning; the precise answer would be a reporting of your
experimental error!)
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Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
5. What could you have done to have improved the accuracy of the number reported in question 4?
(Even if you had 0% error, consider the question and offer a good answer!)
Mass, Volume and Density of Distilled Water
Results
6.
Measurement
Mass of Graduated Cylinder
(g)
Mass of Graduated Cylinder +
Water (g)
Inst. Signature
Not required if
using electr scale
Not required if
using electr scale
Volume of Distilled Water
(mL) in 10 mL grad cylinder
Volume of Distilled Water
(mL) in 100 mL grad cylinder
Analysis
7. Calculate the mass of the water sample by subtracting the mass of the 10 mL graduated cylinder
from the mass of the 10 mL graduated cylinder + water:
8. Calculate the density of the water sample by dividing the calculated mass (g) by the volume
(mL):
density =
mass
volume
1.16
Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Discussion
9. The known density of water at 3.98°C is 1.0000 g/mL. Why wasn’t this the density you
obtained? (Or was it?)
10. What is the relationship between temperature and density?
Temperature, Boiling and Melting Points of Water
Results
11.
Measurement
Inst. Signature
Room Temperature of Water
(°C)
Boiling Point of Water (°C)
Freezing/Melting Point of
Water (°C)
Temperature of Ice with NaCl
Added (°C)
Analysis
12. The known boiling point of water (at sea level, 1.00 atm, 760 torr) is 100°C (more precisely
written 1.00 x 102°C) and the known melting point of water is 0.00°C (at sea level, 1.00 atm, 760
torr). Calculate the experimental error between your experimental values and the known values.
[IMPORTANT NOTE: Since you can’t divide by zero, you must convert degrees centigrade into
degrees Kelvin. To do this, add 273 to all of your temperature determinations before using the %
error calculation!]
1.17
Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Discussion
13. What did salt do to the melting point of water? Why did this happen?
14. Organisms that live in the Arctic and Antarctic seas live in water that is at or below freezing, yet
the water in which they live doesn’t freeze. Why?
The Scientific Method: Ht/W Ratio of a Gastropod Shell
Results
15. Gastropod species studied: ______________________________________________________
16. Height/width ratio of initial gastropod shell: ______
17. Hypothesis: __________________________________________________________________
18. Data Table: Height (Ht.), width (W) and height/width ratio (Ht/W) of gastropod shells, in
millimeters.
Snail
#
1
2
3
4
5
6
7
8
9
10
Ht
W
Ht/W
Snail
#
Ht
W
11
12
13
14
15
16
17
18
19
20
Ht/W
Snail
#
21
22
23
24
25
26
27
28
29
30
1.18
Ht
W
Ht/W
Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
Analysis
19. Mean value (average) for total Ht/W ratios: _______
Discussion
20. Does the mean Ht/W ratio value support or cause you to reject your hypothesis? Justify your
answer!
Some Additional Problems
Unit Analysis Conversions
10. Using unit analysis, calculate the number of inches in 12.98 meters. Show the unit analysis
equation necessary to solve this problem!
11. Using unit analysis, calculate the number of milligrams in 1.32 pounds. Show the unit analysis
equation necessary to solve this problem!
1.19
Putman’s Biol 160 Lab 1: Metric Measurement and the Scientific Method
12. Using unit analysis, calculate the number of liters in 23.8 gallons. Show the unit analysis
equation necessary to solve this problem!
13. A thermister (electronic thermometer used in oceanography) is incredibly precise but not very
accurate. You don’t want to throw it out as it costs $2000. What can be done to improve its
accuracy?
1.20