Lab 2: Microscopy and the Metric System
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. Exercise 1: Measuring Length, Weight, Volume, and Temperature Try the following conversions for practice. 40,000 ng =0. 24mg =0. 00024g50 cm =500 mm =0. 5m 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? 10, in a meter (m)? 1000 (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: ID card . 5 cm=85mm=0. 085m 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? This is so the original liquid does not get contaminated. 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? Chemicals could go into your mouth, which is potentially dangerous and should never be done no matter if they deemed “safe” or not. Weight: Use the pen scale from the lab kit to measure out exactly three grams of sugar. Make sure to tare the bag before adding the sugar. Why must the bag be tared before adding the sugar? This is done so the weight of the bag is not counted with the weight of the sugar. You must think about the weight of the bag when weighing out the three grams of sugar. How is the weight of the bag accounted for when the sugar is weighed?
The bag is weighed first and then the 3 g of sugar is added on top of that weight so at the end the weight is more than 3g total due to the bag. Temperature: Practice converting the following with this conversion formula: 45°F = 7. 2 °C 62°F =16. 7 °C 98. 6°F =37°C 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: Cold-15°C Warm – 29°C Hot- 48°C Questions A. What laboratory equipment would be used to measure the following items? g flour| Beaker and scale| 36 mL water| Graduated cylinder| The length of a frog’s leg| ruler| 36 g water| Beaker/balance| 38? C| thermometer| Volume of a turtle*| Water displacement| 125? F| thermometer| Volume of blood| Graduated cylinder| Weight of a plant| Bag and scale| Weight of blood| Beaker and scale| Temperature of a fish’s body| thermometer| Temperature of blood| thermometer| *This answer may require some creativity. How could it be done? 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| = 248,000 mg| 145,000 ? L| = 145mL| 536 mL| = 536 cc| 0. 372 kg| = 372 g| 0. 75 L| = 750,000 ? L| 20. 39 cm| = . 2039 m| 145,000? L*(10^-6L /1? L)*(1000mL/1L)=145mL .372kg*(1000g/1kg)=372g 20. 39cm*(1m/100cm)=. 2039m 145,000? L*(10^-6L /1? L)*(1000mL/1L)=145mL .372kg*(1000g/1kg)=372g 20. 39cm*(1m/100cm)=. 2039m 248g*(1000mg/1g)=248,000mg 536mL*(1cc/1mL)=536cc 0. 75L*(1? L/10^-6L)=750000 ? L 248g*(1000mg/1g)=248,000mg 536mL*(1cc/1mL)=536cc 0. 75L*(1? L/10^-6L)=750000 ? L 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= . 711 L7,893 mg = . 0174 lb 2. 25 oz= 66. 53 cc36? C= 96. 8 ? F 7893mg*(1lb/453592mg)=0. 0174lb 36? C*(9/5)+32=96. 8? F (96? F-32)*(5/9)=35. 56? C 7893mg*(1lb/453592mg)=0. 0174lb 36? C*(9/5)+32=96. 8? F (96? F-32)*(5/9)=35. 56? C 3 cups*(. 237L/1cup)=. 711L 2. 25oz*(29. 57cc/1oz)=66. 53cc 145,000uL*(1tsp/4928. 92uL)= 29. 42tsp 3 cups*(. 237L/1cup)=. 711L 2. 25oz*(29. 57cc/1oz)=66. 53cc 145,000uL*(1tsp/4928. 92uL)= 29. 42tsp 45,000 uL = 29. 42 tsp96? F= 35. 56 ? C D. What advantages does the metric system have over the English method of measurement? What are the disadvantages? The metric system is advantageous because it has a base of ten, making measurements easier to take, read, understand, and convert. The prefixes are also standard so they transfer between all measurements. Also, more countries use the metric system whereas basically only the US uses the English method. The main disadvantage of the metric system is that Americans have not grown up with these measurements so they are harder to picture and understand what distance, weight, etc. ach measurement is. For example, it is much easier for most Americans to understand the distance of a mile than to try and picture how long a kilometer is. E. Outline the steps necessary to accurately weigh 3. 5 g of starch. This depends on the scale used, but with the pen scale included in the labpaq, tare a bag or other container that can be used. Then add in the starch until the weight on the scale reads the weight of the container plus 3. 5 g. F. Outline the steps necessary to accurately pipet 5 mL of distilled water. Pour an aliquot of distilled water into a clean beaker.
Put a little more than 5mL of distilled water in a beaker. Pipet 5mL from the beaker, and check to see if the bottom of the meniscus lines up with the 5mL line. 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? 400nm at 2000x? 20 ? m What is the equivalent size at these magnifications, in inches? Show your calculations. 400nm*(1cm/10^7nm)*(1in/2. 54cm)= 1. 57*10^-5 in. 20? m*(1cm/10^4? m)*(1in/2. 54cm)= 7. 87*10^-4 in.
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. 1nm*(1cm/10^7nm)*(1in/2. 54cm)= 3. 94*10^-8 in. 100 ? m*(1cm/10^4? m)*(1in/2. 54cm)= 0. 0039 in. 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. 15x 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? 4x ii. The low-power objective is slightly longer than the scanning objective. What is its power? 10x iii.
The high-power objective is longer than the low-power objective. What is its power? 40x Label this microscope diagram with the appropriate part names and their functions: Eye piece- lens that you look through Body tube- Piece that leaves distance between lenses Course adjustment knob- adjusts focus Nosepiece- turns the lenses Objective lenses- magnify objects Stage- holds slides Mirror- reflects light so you can see what’s on the slides Base- bottom of microscope allowing stability Arm- Supports the tube and connects everything Eye piece- lens that you look through Body tube- Piece that leaves distance between lenses
Course adjustment knob- adjusts focus Nosepiece- turns the lenses Objective lenses- magnify objects Stage- holds slides Mirror- reflects light so you can see what’s on the slides Base- bottom of microscope allowing stability Arm- Supports the tube and connects everything a b c d e f g h i Parts not included in microscope are: Light source Source: Sharma, Abhishake. Labeled Microscope Drawing. N. d. Buzzle. com. 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? The liquid could come off of the slide and get into a place in the microscope that isn’t good for it, and it will be messy also. 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. . 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, viewand then draw the letter here, as it appears onthe slide on the stage. | e e 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? When I move the slide up, what I’m viewing moves down. When I move the slide to the left, the image moves right. . 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? Only a piece of the top part is viewable. Higher power objectives magnify the image more. 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 LensesMagnification =| Total Magnification| 15x| 4x| 60x| | 10x| 150x| | 40x| 600x| 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 ? m 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 ? m. How might this information be useful when viewing microscopic subjects? Micrometers are smaller, so it is useful for very small objects when mm would be a very small number that wouldn’t be very understandable. Table 2: Diameter of a Viewing Field | Magnification(ocular x objective lens’powers)| mm diameterof field of view| ? m diameter *of field of view| Scanning Lens| 60x| 2mm| 2000 ? m| Low Power Lens| 150x| 1mm| 1000 ? m| High Power Lens| 600x| Can’t tell,