BIO 32- Environmental Science Lab
Raskoff
Lab 1- Measurement, Graphing, and Computers
Purpose
In this lab you will use the various measuring tools to learn how to measure and report
your measurements correctly.
Objectives
Measure length, volume, mass and temperature in the SI system using appropriate tools
and analyze the data with computer graphing.
Materials
Metric Ruler
Balance
pH meter
pH paper
Thermometer (lab)
Beaker
Ice
Tap water
Sea water
Thermometer (digital)
Pasco unit w/ temp probe
Refractometer
Hydrometer
Conductivity meter
Lab Laptop computers
Background
Measuring is an important activity in science. Measurements provide precise
observations that are not subject to interpretation as are qualitative observations. For
example, a measurement reported as 2.0 cm is the same to everyone, while a report that
some chemical turned "burnt orange" can mean different shades to different people—to
someone who is color-blind, it may not mean anything! This endeavor is empirical in
nature, being dependent on evidence that is observable by the senses. This evidence can
include purely descriptive data, which we would call qualitative, but often it tries to
make sense of the world through the collection of numerical data, which we call
quantitative. Being able to say a chiton was 4.2 cm long is much more informative than
saying it is “small”, or stating that the water is 3º C and has a salinity of 33 is much more
useful than stating that the water is “cold and salty.”
Scientists use the International System (abbreviated SI, from the French version of the
name) for measuring. This system is based on the metric system. As you probably know,
SI units are based on powers of 10. The sizes of the units in the metric system are based
on measurements of water and the earth. The metric system is used by scientist
throughout the world. It is also used in everyday life in most countries. If you think you
are not familiar with a system based on 10, think about this…. Money – ten cents to a
dime and ten dimes to a dollar. To convert from pennies to dollars and back again is
simply a matter of moving a decimal point (100 cents is 1.00 dollars), same as in the
metric system of measurement. For example, if you measure something and it is 135
millimeters and you need to convert it to meters, just move the decimal point three places
to the left and you are at 0.135 meters. Try to convert 135 inches to yards – not that easy
is it?
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The basic unit of length is the meter. A meter is a little larger than one yard. Larger and
smaller units are based on powers of 10 according to this pattern:
Prefix
mega
kilo
hecto
deka
BASE UNIT
deci
centi
milli
micro
nano
pico
Abbreviation
M
km
Hm
Dm
l, g, m, etc.
d
cm
mm
u
n
p
Division of metric
unit
1,000,000
1,000
100
10
1
0.1
0.01
0.001
0.000001
0.000000001
0.000000000001
Examine a metric ruler. The numbered units are centimeters. A centimeter is a little
smaller than half an inch. Each centimeter is divided into 10 smaller spaces. Each of
these spaces is a millimeter. That means 10 mm = 1 cm, or 1 mm = 0.1 (or 1/10) cm.
Do not mix units in measurements. For example, if a certain object measures 4 whole
centimeters and three little marks, you write 4.3 cm. The ".3" counts the "three little
marks." You do not write 4 cm 3 mm as in the English system of measurement
(recording feet and inches). Since each whole centimeter is 10 mm, you could also write
43 mm (4 x 10, plus the "three little marks").
Mass is another important measurement. The unit of mass is the gram. A gram is
defined as the mass of one cubic centimeter of pure water at a temperature of 4 C. A
dime weighs a little over 2 grams and a nickel weighs about 5 grams. A milligram (mg)
is a thousandth of a gram and isn’t much unless you are dealing with potent drugs. The
only other measure of mass commonly used in the sciences is the kilogram (kg) which is
rather a hefty amount. A fullback would weight about 100 kg.
Volume: The liter (l) is the basic unit of volume and is defined as the volume enclosed
within a cube 10cm x 10 cm x 10 cm. It shouldn’t be too difficult to see that a liter
contains 1,000 cubic centimeters (cc). The liter has made it’s appearance in grocery
stores in the form of 1 liter bottles of water and 2 liter bottles of soda, there are even 3
liter bottles out there. Commonly used units of volumetric measure other than the liter
include the milliliter (ml) and the deciliter (dl). A milliliter is about the volume of saliva
in one spit from a baseball player. A soft drink container holds about 4 deciliters.
Temperature is another important measurement. The SI system uses the Celsius
temperature scale. A Celsius degree is almost twice as large as a Fahrenheit degree.
From freezing to boiling is 32F to 212F, but only from 0C to 100C. To get a better
understanding of the Celsius scale, consider the following common temperatures:
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21C = the temperature in a comfortable room
75C = the temperature of a hot cup of coffee
37C = human body temperature
40C = the temperature of a hot summer day
Learning to use measurement tools correctly, and to report your results accurately is an
important skill. In this lab you will practice measuring correctly and perhaps discover
some other interesting things about your measuring tools.
The non-living, or abiotic factors are often important in studies of the environment.
These can include both physical and chemical factors, such as location, temperature,
light, pH, wave force, wind, toxins, etc. The huge array of abiotic factors often are
measured by a large variety of different tools, many of which can measure the same thing
in different ways, with different units. A trend in recent years with the miniaturization of
sensors, probes, and computer technology is the creation of multipurpose tools which can
measure many different abiotic factors, sometimes all at once. Using some nifty tools,
we will get some hands on experience measuring some abiotic factors and practice
graphing the results!
Procedures
Length
1. Measure a book in centimeters. Record your measures in the Data Table. Measure
the length, width, and height. Length is the longest measure, no matter how the
object is oriented, height is the smallest measure. Convert your measures to
millimeters.
2. Use your ruler to measure the thermometer and an electric switch plate (the wallguard where you turn on a light). Measure in millimeters. Record your measures
in the Data Table. Convert your measures to centimeters. So, can you measure
length, width and height on these?
Length Measurement
Item Measured
L
Measure in Centimeters
W
H
L
Measure in Millimeters
W
H
Book
Electric Switch plate
Thermometer
Mass
1. Use a laboratory balance to measure mass. You must first “zero” the balance. I
will show you how to do this. You just place the object on the balance and
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record the reading. Find the mass of a book (any small book), a pencil, and a coin
(any coin). DON’T drop the things on the scale, be gentle.
2. Now you will find the volume of the book you measured. Look back in the
background info if you need to for this. But remember volume = length x width x
height. So, what is the volume of the book you measured? Record this on the
data table.
Mass Measurement
Item
Mass
Book
Pencil
Coin – list what you
measured
(ex. Penney, dime)
Volume of Book, in milliliters: _____________
pH determination
1. You will spend time examining pH, a measure of the acidity of a solution in terms
of activity of hydrogen ions (H+).
2. Record the pH values of the three solutions A, B, and C using the pH paper and
the digital pH meter. Do the values agree?
Solution
Distilled Water
pH Paper
pH Meter
Solution “A”
Solution “B”
Solution “C”
Salinity

Salinity, the amount of dissolved solids in a solution can be measured in several
ways, including: electrical conductance; measuring changes in density of the
liquid with a hygrometer; and the difference in refracted light with a
refractometer. It is usually measured in “parts per thousand (‰).”
There are several different methods of the testing the amount of dissolved solids, or
salinity, in solutions. You can determine salinity using the difference in the refraction of
light through a sample. You can also measure the density of the solution with a floating
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hydrometer. Electrical conductance is also commonly used, the higher the salinity in the
water, the more easily current can flow.
1. Using the hand-held refractometer, determine the salinity of the two solutions.
Place a drop of the solution on the glass plate and put the cover down on the drop.
While holding it up to the light, look in the scope and you should see a shadow
line which is where you read the sample. Make sure you read the number from
the right side of the meter (‰).
Refractometer
Hydrometer
2. Using the glass, floating hydrometer, determine the density of the samples by
letting it float until still and then read the measurement off of the scale inside the
glass. You’ll need to convert the number you read into ‰ with the conversion
tables. Note: you need to know the temperature of the liquid!
3. Using the digital conductivity meter, measure the salinity of the three samples
again. Follow the printed directions carefully. How do the three values compare?
Solution
Tap Water
Refractometer
Hydrometer
Conductivity Meter
Sea Water
Temperature
Several different temperature measuring devices have been put into two beakers of liquid.
1. Record the temperature on each device for each liquid. Which device is most
accurate? How do you know?
Pasco
Digital
Lab
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Solution
Beaker 1
Pasco
Digital
Lab
Beaker 2
Graphing Laboratory
“A picture is worth a thousand words”, is a common phrase, and this is just as true
in science. Why use graphs? Data, events recorded digitally, are often not very
interesting in and of themselves. We are interested in the potential relationships that may
lie buried within data but our brains are not very good at seeing these relationships in
columns of numbers. If we plot these data on a coordinate system, relationships within
the data, may be laid bare before our eyes. Learning to make meaningful pictures from
numerical data and learning to interpret these pictures is part of being a scientist.
The purpose of this lab is to illustrate the usefulness of graphs, to teach you how
to compute and graph with Excel, and to get you to think about how to present your
numerical data in meaningful graphs.
Outcomes
Be able to use Excel:
A) learn how to read graphs
B) to make different kinds graphs using Excel
C) to calculate average and standard deviation of data sets
Exercise 1
Making Scatter Graphs in Excel
To make a graph in Excel, first open a new worksheet. You have before you a
page with many columns of cells. Each cell has a numerical coordinate (along the left
axis) and an alphabetical coordinate (across the top). Enter the following data in columns
A and B (figure 1).
Figure 1
Figure 2.
Figure 3.
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For the purpose of the exercise, let us say that you have a job making $10 per hour and
want to graph your earnings. You will graph time in hours on the X axis and dollars
earned on the Y axis.
1. Select your numbers.
2. To tell Excel what data to plot, select (click and drag) the cells you would like to
use and select Insert  Chart from the top menu (figure 2).
3. Now select the type of chart you would like to use, such as the first one, which is
what we will use in this example (figure 3). CHOOSE XY SCATTER.
4. Click NEXT
A graph will appear with the A column as your X (independent) variable, and the B
column graphed as the Y (dependent) variable, click next and you will then be prompted
for a variety of information such as the names of your X-axis, your Y-axis, chart title, etc.
(figure 4).
5. In the “Chart Title” box type “Dollars per hour”
6. Now enter your Y and X axes information as Hours and Dollars.
7. Click “next”
8. Next choose to place your graph on its own sheet. Give it a name. (figure 5)
Figure 5.
Figure 4.
9. A graph will appear that should look like this (figure 5).
Figure 5.
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Exercise 2
Bar or Column Graphs
You are testing for the number of E. coli bacteria per liter of water from Moro Cojo
Slough. The following data are four replicates collected from 6 different sites on the
same day.
E. coli per liter of Water
Rep1
Rep2
Rep3
Rep4
Mean
StDev
Site 1
3
5
7
12
Site 2
12
12
12
12
Site 3
22
23
22
24
Site 4
1
2
1
3
Site 5
40
34
55
33
Site 6
12
4
5
7
1. First enter the data in the table above in an excel spreadsheet
2. Determine the Average (MEAN) for each site and the Standard Deviation for each
site.
To calculate the average, click on the first empty cell in Site 1. Then go to “Insert” on
the main menu and choose Function (there is also a fast button on your tool bar for this –
it looks like fx – if you use the funny letter F option, select your numbers and chose
“Average”). A dialog box will appear and will give you lots of choices. Go to
“Statistical” on the left and “Average” on the right (Figure 1). Click “OK”. Another box
will appear, now pop back to your worksheet and select all the number you want to get
the average of (all numbers in Column “A”), you may need to move this new box out of
the way to see your data; click OK and the average of those numbers should appear
(Figure 2).
Figure 1
Figure 2
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To quickly put the same formula in the next 5 boxes, to get all the averages, you can “fill
in” the formula into those boxes by selecting the bottom right corner of the box that has
the average in it (cursor changes to a little + sign) (Figure 3). Drag that little + sign
across the other cells to automatically calculate the averages.
Figure 3.
Figure 4.
Now you need to determine the Standard Deviation of your data set. Go to the new cell
and do the function again – this time choosing STDEV (that is short for Standard
Deviation). Use the same concepts you just used for Average, but this time you are doing
STDEV. Fill in the other cells like you did with the averages. You will need to follow
the more detailed directions above. What does this number mean?
3.
4.
5.
6.
7.
8.
Select only the calculated means, then hit the graph button (or menu option)
Choose your graph type – column or bar
Click “next”
Fill in chart title and label the axes
You should have a bar graph of the six means (see below, but without the lines).
To add your standard deviations, click on a bar on the graph and a dialogue box
will pop up.
9. Click on “Y error bars”
10. Click on “BOTH” for Display
11. Click on Custom and in the “+” and “-“ boxes click back on your worksheet and
select all six of the StDev numbers you calculated. The same formula should be
in both the “+” and “-“ box.
12. Click OK and you should see all error bars plotted on the bars– NOTE –for Site 2
notice the data was all the same; so the StDev was 0, so there is no bar. Check
that the bars are different sizes! If not, something went wrong.
13. You now have a graph with six bars on it.
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Your graph should look something like this.
E. Coli in Moro Cojo
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Number of E. coli per liter
50
40
30
Average
20
10
0
1
2
3
4
5
6
Site Location
Explain your graph in writing below the figure.
Make sure your graphs all have titles, legends and the x and y axis are labeled correctly
so the graph makes sense.
To turn in (either today or next week)

Turn in both graphs (a scatter, a bar).
 Turn an explanation for your bar graph – in other words – what does all this
mean, what are your interpretations of the data? What sites had the most and
least bacteria. What areas had the most variation (StDev), which had the
least?
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