BIO LABS

44-0090-00-01_rpt_microscopy_and_the_metric.pdf

Microscopy and the Metric System Margaret E. Vorndam, M.S. Version 42-0090-00-01

Lab Report Assistant This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Observations

Data Table 1: Calculating Magnification Ocular Lens Magnification x

Objective Lenses Magnification = Total Magnification

Data Table 2: Diameter of a Viewing Field Magnification (ocular x objective lens’ powers)

mm diameter of field of view

μm diameter * of field of view

Scanning Lens Low Power Lens High Power Lens

www.HOLscience.com 111 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

Exercise 1: Measuring Length, Weight, Volume, and Temperature Try the following conversions for practice.

240,000 ng = mg = g 50 cm = mm = m

Procedure 1. Length: A metric ruler is useful for measuring items of length. The ruler below measures in

mm, indicated by the small mm near 0.

a. How many mm are there in 1 cm? , in a meter (m)?

(Ruler is not to scale. See ruler in dissection kit.)

b. Locate a measurable object to use for this exercise. If the object is long, obtain a yardstick that includes a cm scale; they can be found in local hardware stores.

c. Record the length of the object below and do the conversions:

Name of object _________________

Volume: Always pour an approximate volume of liquid into a clean beaker and then from the beaker into the volumetric flask or graduated cylinder. This will minimize contamination of the parent liquid source. Dispose properly of any leftover liquid. Do NOT pour it back into the original container. Why?

When using a pipet or dropper to measure liquid, pour an aliquot into a clean beaker and then draw up the liquid from the beaker into the pipet. NEVER try to draw up chemicals by mouth. Why?

www.HOLscience.com 112 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

Weight: Use a piece of paper and the digital scale from the lab kit to measure out exactly three grams of sugar. Make sure to tare the scale with the paper before adding the sugar. Why must the scale be tared before adding the sugar?

Temperature:

Practice converting the following with this conversion formula:

45°F = __°C 62°F = __°C 98.6°F = __°C

45°F = 62°F = 98.6°F =

Use a Celsius thermometer to measure the °C temperature of several different aliquots of cold and warm tap water. Make sure to allow the thermometer to remain until the temperature is stable and no longer changes. Record the temperatures:

________°C ________°C ________°C

Questions A. What laboratory equipment would be used to measure the following items?

5 g flour 36 mL water

The length of a frog’s leg 36 g water

38ºC Volume of a turtle*

125ºF Volume of blood

Weight of a plant Weight of blood

Temperature of a fish’s body Temperature of blood *This answer may require some creativity. How could it be done?

www.HOLscience.com 113 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

B. Provide the calculation steps, including the conversion factor that would be needed to convert the following measurements, and the final answers. Use U.S. and liquid units where appropriate.

248 g

= _______ mg 145,000 μL

= _______mL

536 mL = _______ cc 0.372 kg = _______ g

0.75 L

= _______ μL 20.39 cm = _______ m

www.HOLscience.com 114 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

C. Provide the calculation steps, including the conversion factor that would be needed to convert the following measurements, and the final answers. Use US and liquid units where appropriate.

3 cups = __________ L 7,893 mg = __________ lb

2.25 oz = __________ cc 36ºC = __________ ºF

145,000 uL = __________ tsp 96ºF = __________ ºC

www.HOLscience.com 115 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

D. What advantages does the metric system have over the English method of measurement? What are the disadvantages?

www.HOLscience.com 118 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

E. Outline the steps necessary to accurately weigh 3.5 g of starch.

F. Outline the steps necessary to accurately pipet 5 mL of distilled water. Pour an aliquot of distilled water into a clean beaker.

Exercise 2: Microscopy The compound light microscope effectively magnifies in the range of 40x to 2000x. If an object under view is 10 nm in length without any magnification, what will be its viewing size at 40x?

at 2000x?

What is the equivalent size at these magnifications, in inches? Show your calculations.

The scanning electron microscope (SEM) employs electron bombardment to image very small specimens. Electron microscopes are used to image specimens that range from 1 nm to 100 µm in size. What is the equivalent in inches? ______. Show your calculations.

www.HOLscience.com 119 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

Procedure 1. Parts of the Compound Light Microscope: Refer to a microscope as this section is read. Label

the microscope diagram that follows as the examination of the microscope proceeds.

a. Eyepiece (Ocular Lens): The magnification power is stamped on the outside of the lens. What is the power of the ocular lens? Microscopes may have interchangeable ocular lenses of different magnification.

b. Body Tube: Holds the ocular and objective lenses at the correct focal distance.

c. Arm: Used to transport microscope and hold the body tube.

d. Nosepiece: The revolving device that holds the objective lenses. May also be referred to as the turret.

e. Objective Lenses: Consists of one or more lenses:

i. The scanning power objective lens is the shortest of the lenses. What is its power?

ii. The low-power objective is slightly longer than the scanning objective. What is its power?

iii. The high-power objective is longer than the low-power objective. What is its power?

Label this microscope diagram with the appropriate part names and their functions:

www.HOLscience.com 120 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

Parts not included in microscope are:

www.HOLscience.com 121 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

2. Focusing the Microscope:

If the microscope includes an oil immersion lens, place a drop of immersion oil on the slide cover slip before rotating the lens into place. The function of the oil is to minimize light diffraction through the slide and subject so that greater detail can be seen. After using the oil immersion lens, clean excess oil off of the lens and the slide with a lens cloth. Never tilt a microscope when using oil or if viewing a wet slide. Why?

3. Operating the Microscope:

a. Obtain a clean slide and cover slip from the slide box. Place the slide and cover slip separately on a paper towel or other soft surface to reduce the possibility of scratching them.

b. With scissors, cut a letter “e” from an old magazine or newspaper.

c. Place the letter in the center of the slide.

d. Follow the instructions in Section 6 below to make a wet mount of the letter.

e. Following the directions outlined above under Handling and Focusing the Microscope, place the prepared slide on the microscope stage. Leave the scanning lens in place and focus so that the letter is clearly viewable. Make drawings of the letter in the boxes below as instructed.

Side of the slide furthest away from student

Look from the side of the microscope, view and then draw the letter here, as it appears on the slide on the stage.

Draw the letter here as it appears when viewing it through the microscope.

Side of the slide closest to student

f. What is observed? Microscopes invert the image on the slide. This means that the subject will appear to be 180° rotated and reversed from the actual image viewed on the slide.

g. While viewing the letter through the lenses, move the slide slightly. What do you observe about the movement of the letter and slide when viewed through the lenses?

h. Use the directions above to view the letter at the higher objective powers. On the drawing made above, circle the portion of the letter that is viewable as successively higher power observations are made. What is your conclusion about what happens when higher power objectives are used?

www.HOLscience.com 122 ©Hands-On Labs, Inc.

Experiment Microscopy and the Metric System

4. Total Magnification Calculation: Typically, the ocular lens of a microscope will be 10x, but it may be higher or lower. The power is recorded on the side of the lens.

a. What is the ocular lens power of the microscope that you are using? It may be 10x or 15x. Record it in Table 1.

b. The objective lenses also have the magnification power recorded on their sides. What powers do the objective lenses on the microscope have? Record them in Table 1.

c. Now, calculate the total magnification of the viewing area by multiplying the power of the ocular lens with that of the objective lens in use. For instance, if a microscope has a 10x magnification ocular lens and a 4x objective lens in place for viewing, the total magnification will be 40x (10x multiplied by 4x). What other view magnifications are possible with the microscope? Calculate the total magnification for each set of lenses in Table 1.

Table 1: Calculating Magnification

Ocular Lens Magnification x Objective Lenses Magnification = Total Magnification

5. Diameter of Field:

a. With the low-power objective in viewing position, place a short transparent metric ruler on the stage.

b. While viewing the ruler through the lenses, measure the low-power diameter of field of view in mm. Convert this measurement to μm and record in Table 2.

c. Switch to the other higher power objectives, noting the diameter, in mm, for each in Table 2. Convert measurements to μm. How might this information be useful when viewing microscopic subjects?

Table 2: Diameter of a Viewing Field

Magnification (ocular x objective lens’

powers)

mm diameter of field of view

μm diameter * of field of view

Scanning Lens Low Power Lens High Power Lens

Experiment Microscopy and the Metric System

6. Depth of Field: Prepare a wet mount slide of three differently colored crossed threads using the wet-mount technique described above. Place the slide on the microscope stage with the thread crossing area in the center of the viewing area. Focus carefully, moving the scanning objective lens up and down, taking care not to break the cover slip.

Record the order of the threads in this table. Note that, when one thread is in focus, the others appear blurred. Why? When you focus on another thread, what happens to the thread that you were viewing?

Depth Thread Color

Top Middle Bottom

Switch to high power and focus on one thread, then focus on another thread. What do you notice about the depth of field? Can you see as much of the thread in focus at the high power as you could at the low power magnification?

7. View an animal cell:

a. Observe the prepared slide under the microscope, beginning with the scanning lens and then proceeding to higher magnification levels. Locate the nucleus in several cells. Locate the cytoplasm and the plasma membrane. On a sheet of paper, make a drawing of a few cells, and label the observed parts.

Experiment Microscopy and the Metric System

8. View a plant cell:

a. Observe the slide under the microscope, beginning with the scanning lens and then proceeding to higher magnification levels. Locate the cell wall and the nucleus in several cells. Make a drawing of a few cells and label the observed parts.

b. Count a column of cells, stacked end-to-end, across the field of vision under high-power magnification.

c. F. Based on the field of vision measurement you calculated above, compute the average length of one cell in the column of cells with this formula:

μm average length of cell = μm diameter of field of view ÷ total number of cells in the column.

Experiment Microscopy and the Metric System

d. What differences were noted between the animal cells and the plant cells?

e. How do the differences dictate the form of the organism?

Discussion A. What is the purpose of staining cells before viewing them under a microscope?

B. What type of microscope would you use to view the following organisms? There may be more than one correct response for each.

Strep throat culture Mitochondria in an animal cell

Structure of a bird feather Chloroplasts in a leaf cell

Earthworm digestive system Enterococcus bacteria

DNA structure in the nucleus Spores from a mushroom

Cells from plant leaf Herpes simplex

Experiment Microscopy and the Metric System

C. Summarize the capabilities of each of the microscopes listed in Table 2-3 below.

Table 3: Summary of Microscope Capabilities

Type of Microscope Type of Detection Beam Magnification Range, metric

Examples of Viewable Specimens

Dissecting

Compound Light

Scanning electron

Transmission electron

Experiment Microscopy and the Metric System

Laboratory Summary 1. What have you learned from doing this laboratory?

2. Why is the information presented in this laboratory intrinsic to all future studies in biology?

Experiment Microscopy and the Metric System