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Measurement & Lab Equipment Abstract This lab reviews the concept of scientific measurement, which you will employ

weekly throughout this course. Specifically, we will review the metric system so that you will be

able to measure length, mass, volume and temperature in metric units, and convert between the

English and metric systems. You will also familiarize yourself with common laboratory

equipment. You will review and practice scientific notation so that you will understand its use in

scientific measurement. Finally, you will utilize basic statistical methods to evaluate data that

you gather and graph. The sections entitled “Put what you have read into Practice” will be due as homework next

week. Whatever you do not complete during the lab period should be completed at home.

Conversions within the Metric System Introduction

Length, Mass, Volume To convert within the metric system, you must remember the following:

To convert between metric units, you will need to move the decimal to the right or to the left,

relative to where you begin, as shown by this chart. This means that you will need to add a decimal

to the end of any whole number! For instance “35” is the same as “35.”

Example 1: Convert 5 mg to g. To get from mg to g requires you to move to the left on the

chart 3 units, thereby moving the decimal to the left 3 units. Therefore the value will be 0.005 g.

Example 2: Convert 80 hectoliters to centiliters. To get from hector- to centi- requires you

to move to the right 4 units. Therefore the number will become 800000 cl.

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Example 3: Convert 400 ml to nl. To get from milli to nano requires you to move 6 units to

the right. Notice that we are referring to the exponent associated with 10 when we count places to

move the decimal-­‐ we are not counting actual words listed on the chart. Therefore 400ml becomes

400,000,000 nl.

*Make sure you look at your answer to see if it makes sense! Does it make sense

that 1 liter is the same as 0.001 ml?! No, because milliliters are smaller units than liters! Therefore

you would know that you had moved the decimal the wrong way. One liter is equal to 1000 ml. Important conversions to know about water under standard conditions!

1 cc = 1ml 1dm3 = 1 liter

1 ml = 1 g 1 liter = 1 kg This means that 50 ml of water weighs 50 g. Also, 3 liters of water equals 3 kg.

Check your understanding: If you weigh 142 ml water, how many mg would it equal?

Temperature Temperature can be measured in Fahrenheit or in Celsius. Here in the US we are

used to thinking of temperature in terms of °F. In science we evaluate temperature using the

Celsius scale. It is called the centigrade thermometer because there are 100 (centi) degrees between

the freezing (0°C) and boiling point (100°C) of water. To convert between the two, use the following

conversions: From Fahrenheit to Celsius:

1. Subtract 32 from degrees Fahrenheit

2. Multiply by 5 3. Divide by 9

From Celsius to Fahrenheit:

1. Multiply degrees Celsius by 9

2. Divide by 5 3. Add 32

To get you thinking in terms of Celsius, know the following common knowledge points. This will help you evaluate your answer in terms of “does this make sense”?

Freezing: 0°C = 32 °F

Room Temperature: 21.1°C = 70 °F Body Temperature: 37°C =

98.6 °F Boiling: 100°C = 212 °F

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Example 1:

What is the temperature in °C if the outside air temperature is 43°F? 1. 43-­‐32 = 11

2. 11 x 5 = 55 3. 55 divided by 9 = 6.11 Therefore the answer is 6.11 °C. Evaluate the answer. Does this make sense? Yes, in that you would expect the temperature in Celsius to be less than an equal temperature in Fahrenheit, based on the above “common knowledge” points.

Put what you have read into practice: Convert the following numbers to the units indicated. Indicate what each are measuring-­‐ are they

units of mass, volume, or length?

1. 5.5 mg = hg Unit of:

2. 61 pl = ml Unit of:

3. 110 m = km Unit of:

4. 7.89 dg = µg Unit of:

5. 0.003 km = mm Unit of:

Convert the following temperatures as indicted. You must show your work. Do not use a calculator!

6. 83 ◦F = ◦C 9. 98 ◦C = ◦F

7. 22 ◦C = ◦F 10. 62 ◦F = ◦C

8. 4 ◦C = ◦F

Converting from English to Metric Units Converting from English to metric units:

The basic metric unit of length is the meter. To compare English and metric values of length, it is

handy to know that 1 inch = 2.54 cm. Mass is expressed in grams. To compare English and metric values of mass, it is handy to know that 1 kilogram = 2.21 pounds.

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Volume is measured in liters. To compare English and metric values of volume, it is handy to know that 1 ounce = 30 milliliters and 1 gallon = 3.8 liters.

Becoming familiar with Laboratory Equipment

In this lab course, you will work with equipment and glassware that is common in the laboratory

setting. Locate the following items.

Graduated cylinder Digital Balance Beaker Graduated Pipette Erlenmeyer flask Weigh boat

Stir Bar Hot/Stir Plate

Measuring Volume: Fill your graduated cylinder with 45 ml of water. When measuring the volume of a

liquid in a graduated cylinder, you will observe a “meniscus.” Locate the meniscus (and include it

in your drawing.) Do you think that you should measure the volume from the top or bottom of

the meniscus? Check with your instructor to make sure you are correct!

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Now transfer the water to your beaker. Is this as accurate at measuring volume as the graduated

cylinder?

Using a Balance: For the digital, practice using each by finding the mass of a coin. To do this, you will need to use a

weigh boat since you typically do not want to place the material you are weighing directly on the

balance.

1. Locate and place the weigh boat on the digital balance. 2. “Tare” the digital balance in order to reset the balance to “0” grams. This will ensure

that you do not add the weight of the weigh boat to what you are weighing. 3. Add the coin. Record the weight of the coin for each.

Digital balance grams

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Put what you have read into practice: Now you will apply the knowledge you have gained. In this section of the lab, you will learn about the

different pieces of laboratory equipment, as well as how to measure the different properties of matter with

them.

Using a Balance:

Digital Balance:

Having improper weights may provide odd results on your experiments. In most experiments

quantities may be crucial to expect accurate results. The digital balance will provide you with the

exact weight of the materials you will need not only on the biology laboratory but in any other labs;

this is why using it carefully is vital for your experiments.

1. Turn on the digital weight.

2. Place a weight boat on the scale.

3. Reset the values of the scale by pressing ON/ZERO button located on the left of the scale.

During a practical, Sally Student and Sid Student were asked to find the weight of a penny on a

digital balance. Sally found that the weight was 0.001 grams whereas Sid found that the weight

was 4.3 grams. The correct answer was 2.5 grams. a. What do you think Sally might have done incorrectly?

b. What might Sid have done incorrectly?

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Understanding Meters: 1. Meters are the base unit of the metric system used to measure length. Please state what

measuring device or devices you would use to measure an object in the following units: 3 mm: 20 cm:

1.5 m:

2. Measure your lecture book (height, length, and width): measure in centimeters (cm) and, if

possible, measure in millimeters (mm). Use the instruments that you listed in #1 to measure these

objects. Write down the name of the item and how many centimeters or millimeters it measures.

Please include the units (cm or mm) with your measurement. 3. Is a centimeter larger or smaller than a millimeter?

4. What property of these items do cm or mm measure: length, volume, mass or temperature?

5. The height of the average person is a little over 1.5 meters. Knowing this, is one centimeter

larger or smaller than one meter?

6. Is one millimeter larger or smaller than one meter?

7. Runners often run a 5K, which is five kilometers (km). Is a kilometer larger or smaller than a

meter?

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Understanding grams: 8. Grams are the base unit of the metric system used to measure the amount of matter in an object.

There are two instruments that you could use to measure something in grams.

9. Weigh a screw and a stopper is measured in grams (g). Write down the name of the item and

how many grams it weighs. Please include the units (g) with your measurement.

10. Find one item that is most likely measured in kilograms (kg). Are you able to measure this

with the instruments that you listed in question 8? Why or why not?

11. Which item felt heavier, the item measured in grams or the item measured in kilograms?

12. Based off of your answer to number 8, is a gram larger or smaller than a kilogram?

13. What characteristic of these items do grams and kilograms measure: length, volume, mass,

or temperature?

14. The other units that can be used to measure these items are either pounds or ounces. These are

commonly used to measure the weight of objects. What property of the item(s) does weight

measure? Is this property the same thing as your answer in number 13?

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Understanding Liters: 15. Liters are the base unit of the metric system used to measure volume. Please list all of the

pieces of glassware that could be used to measure volume.

16. If you were to pick two of these pieces of glassware to measure the volume of a liquid as accurately as possible, which two would you pick? Why?

17. Fill a 100 ml beaker with water to the 50 ml mark and measure with a graduated cylinder

(ml). Write down the name of the item and how many liters or milliliters it measures. Please

include the units (ml) with your measurement.

18. Based off of your answer in number 17, would you be able to place all of the contents of a 2

liter container into a 1000 ml container?

19. Would you be able to place the contents of a 1 liter container into a 600 mililiter container?

What characteristic of the contents of the container do liters measure: length, volume, grams or temperature?

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Scientific Notation Introduction: Scientific Notation is a way of expression very large or very small numbers such

that it is easy to write, easy to determine the value and easy to make comparisons to other

numbers.

For instance:

• the number 342000033994 is a long number to write and difficult to say exactly what that

number’s value is without some thought. Adding commas helps: 342,000,033,994, while

easier to read is still large and long!

• how does 342000033994 compare to 45645612825? How about 342,000,033,994 to

45,645,612,825-­‐ how much bigger or smaller is it? This is very hard to do at a glance! Putting the numbers in scientific notation makes it easy to quickly determine the value and to

compare numbers. Try 3.42 x 1011 vs. 4.56 x 1010? It is much easier to compare these values!

Scientific Notation is NOT difficult, but does require that you follow some simple steps, and that you use your common sense. Follow these steps each time:

1. Rewrite your number and put a decimal point after the *first* non zero digit. For

instance, a. 1234567 becomes 1.234567 and b. 0.001234567 becomes 1.234567

2. Add “x 10” to the end of the digits a. 1234567 becomes 1.234567 x 10

and b. 0.001234567 becomes 1.234567 x 10

3. Count how many place values the decimal has moved from the original placement to

the current placement. Write that number as your exponent.

a. If the number became smaller when you moved the decimal, you will need the

exponent to be positive: 1234567 becomes 1.234567 x 106

b. If the number became bigger when you moved the decimal, you will need the

exponent to be negative: 0.001234567 becomes 1.234567 x 10-­‐3

4. Always check your answers! Do they make sense? For instance: Does 1.234567 x 106 equal a larger number by 6 tens, 1234567? Yes!

What do the exponents mean, at a glance? Remember these values and you will be able to read the

value of very large numbers very quickly. 103: thousands 106: millions 109: billions

10-­‐3: thousandths 10-­‐6: millionths 10-­‐9: billionths

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Put what you have read into practice: Convert the following numbers from full expression to scientific notation.

1. 1,345,635,000

2.

457.430

3.

0.000554433

4.

47777.0055

5.

0.0044551111

Convert the following numbers from scientific notation to full expression.

6. 4.56 x 108

7. 6.785544 x 10 -­‐8

8. 8.992233 x 106

9. 9.11 x 10-­‐2

10. 6.789 x 105

Statistical Calculations

Introduction To analyze data generated in the laboratory in order to determine its significance, you must first

be equipped to evaluate your data from a statistical perspective. A review of basic statistical

terms is included here for your review.

Mean: This is an average of a group of measurements. How to calculate mean?

Add all values and divide by total number of values. • Example: values-­‐ 40, 38, 22, 20, 30 Mean= 40+38+22+40+ 30 divided by 5 = 30

Median: The value that is in the middle of a group of measurements. How to calculate

median? Using previous example:

• Example: values-­‐ 40, 38, 22, 20, 30

Rearrange from low to high-­‐ 20, 22, 30, 38, 40

Median= middle value = 30

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Range: The difference between the smallest and the largest measurements. How to calculate range?

Using previous example:

• Example: values-­‐ 40, 38, 22, 20, 30 Subtract smallest value, 20, from largest value, 40

Range = 40 – 20 = 20

Deviation: Measures how the measurements vary from the mean (+ or -­‐). In other words, what

is the difference between an actual measurement and the mean, or average, of the sample?

How to calculate a deviation? Using previous example:

• Example: values-­‐ 40, 38, 22, 20, 30 We determined the mean to be 30. The deviation for the

value “38” would be +8. This value is 8 more than the mean.

Variance: This measures how much difference, or variation, there is between the values you

have obtained. The smaller the variance, the closer the values will be to the mean. Likewise,

the larger the variance, the farther the values will be from the mean. How do I calculate variance?

Calculate the sum of the squared deviations divided by the number of values minus

one. Using previous example:

• Example: values-­‐ 40, 38, 22, 20, 30 (100 + 64 + 64+ 100

+ 0) = 82 5 -­‐ 1

Standard Deviation: Standard deviation gives you an idea of the widely spread your values

are about the mean. The smaller the standard deviation, the closer your values will be to the

average. If you were to graph data having a small standard deviation, you would expect a

tall, thin bell shaped curve. On the other hand, if the standard deviation were large, your

bell shaped curve would be wider. How to calculate Standard Deviation?

Calculate the square root of the variance. Using previous example:

• Example: values-­‐ 40, 38, 22, 20, 30 The variance equaled 82, to determine Standard Deviation

take the square root of 82 = 9.06

Note: Standard deviation can be used to evaluate the percentage of a population that is near

“average”. One standard deviation to the left and right of the mean will cover 68% of the

population; two standard deviations to the left and right of the mean will cover 95% of the

population.

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Put what you have read into practice: Purpose: In this exercise you will record the gender and height of everyone in the lab. You will

determine the average height of males and females in your lab section.

Materials and Methods: Meter Stick Lab participants

Have each individual list their gender and height on the whiteboard. Record this information in

the data table provided. Where necessary, convert measurements recorded in English units to

metric centimeters. Use the space provided to record deviations (required on next page).

Results:

Males (inches): Males (cm): Females (inches): Females (cm): 1

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20 Figure 1: Height measurements of Biology 1406 laboratory population Use the data from your table to calculate the following, using the information and examples of each given previously (show your work!). Make sure that you use the data expressed in cm, not inches!

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_______________________________________ Size of sample:

Males Females Entire Class ________________________________________________________________________

Mean height:

Males Females Entire Class ________________________________________________________________________

Median Height:

Males Females Entire Class ________________________________________________________________________ Range of height:

Males Females Entire Class ________________________________________________________________________