For this assignment , you have to read only the lab 1 and the instructions to make a study guide notes for the midterm . to make the notes (study guide ) you have to read the instructions first and topics are mentioned under lab 1 in instructions . it has to be plagiarism free . thanks .
Don't use plagiarized sources. Get Your Custom Essay on
â Conversions
â Density and Volume Displacement
â Compound Microscopes vs. Dissecting Microscopes
â Wet Mount Slides
â Depth of Field / Field of View
â Magnification
â Other Relevant Topics
Your notes can be written in whatever format you believe is clearest (bullet points, T-charts,
brief paragraphs etc.) but each lab should consist of roughly 2 pages of notes minimum. Length
will vary based on note format so it may be more helpful to think of this in terms of amount of
time this should take. This assignment is intended to take the place of our in-person class
meeting and should take you roughly the same amount of time as a typical lab might. You should
spend approximately 2 hours creating notes for your section in order to make sure they are
complete and accurate. This study guide is what you and your group members will use to study
for the midterm, so if you miss any important information, you will lose points. Please be
thorough. Notes MUST be in your own words. Simply copying and pasting from lab
materials or the internet will be considered plagiarism. If you are copying images, figures,
etc make sure to note where those were pulled from to avoid plagiarism. Notes should be typed
and organized in âWord-Documentâ format.
Be advised that if your notes are unclear, incomplete, lacking in accuracy, or insufficient in
length that you will not receive full points on this assignment. This assignment is worth 20
points, but it is to your own benefit to complete it as detailed as possible, since this content will
form the basis for your midterm exam, which is worth nearly ¼ of your grade for this class at
Numbers and measurements impact every part of our l
iv
es, and are tools that scientists, engineers, astronauts, chefs and doctors use to analyze data, build bridges, fly orbiters into space, adjust recipes, and prescribe medication. Collecting and analyzing data allows us to understand patterns in the natural world that are not easily observed with the naked eye, and the natural variation that is inherent to all organisms is the major reason we need measurements.
In today’s lab you will learn about basic measurements and common instruments used by scientists on a daily basis. Your ability to learn and use these concepts will be tested and reinforced throughout the semester.
Task 1 – MEASUREMENTS IN SCIENCE: Familiarize yourself with the metric system.
Recall from last week that a key component of the scientific method is experimentation. This step is necessary for the collection of data that will either lend support to, or lead to the rejection of, the hypothesis being tested. In general, data can be qualitative or quantitative. Qualitative data describe variables based on quality (e.g. smell, appearance, texture, etc) and are usually gathered through interviews, pictures, field notes and/or surveys. Quantitative data define the quantity of a variable through measurements (e.g. length, area, cost, height, age, etc.). The main disadvantage of qualitative data is that they are often too subjective (what smells good to one individual might not smell equally well to another). Therefore, quantitative data, which can be statistically manipulated and analyzed, are the preferred choice of most scientists because they provide objective, less biased measures. However, we will examine both types of data in greater detail throughout the semester.
The metric system is used as the international standard to make measurements worldwide. It is based on units of ten (see Table 1 and 2). In contrast, the Imperial Units of Measurement is based on historical precedent, e.g., a foot was first measured as the length of a man’s foot. Because the metric system is widely employed throughout the scientific arena, it will be covered in this lab.
Table 1:
Prefix
Abbreviation
Division or Multiple of Metric Unit
Pico
p
0.000000000001
Nano
n
0.000000001
Micro
µ
0.000001
Milli
m
0.001
Centi
c
0.01
Deci
d
0.1
Base
unit
—–
1
Deka
da
10
Hector
h
100
Kilo
k
1000
Mega
M
1000000
Giga
G
1000000000
Table 2:
Unit (abbreviation)
Measures
Meter (m)
Length
Liter (L)
Volume
Gram (g)
Mass
Degree Celsius (°C)
Temperature
In this task you will practice measuring length, temperature, volume and mass using the metric system. When taking measurements, we often need to convert between units. In order to do this, we must first have information about the size of the unit we are interested in converting to or converting from. Table 1 provides a partial list of these measures. For example, suppose we know that the length of a table is 1.5 meters, but we want to know how many centimeters this corresponds to. Based on Table 1, we know that the “centi” prefix means 0.01. Therefore, a centimeter (cm) equals 0.01 (one hundredth) of a meter (m), or there are 100cm in 1m. To calculate the number of cm in 1.5m, we can either:
(1) Divide 1.5 by 0.01 ? 1.5m x (1cm/ 0.01m) = 150cm or 1.5m / 0.01 = 150cm
(2) Multiply 1.5 by 100 ? 1.5m x (100cm/1m) = 150cm
In both examples, the meters cancel out, leaving the answer in centimeters.
I.
CONVERSIONS
Convert the following measures:
2 meters
=
200
centimeters
=
2000
millimeters
87 millimeters
=
0.087
meters
=
8.7
centimeters
II.
MEASURING LENGTH
This sheet is 8.5 inches by 11 inches. Convert these values to centimeters and then calculate area (in cm) of the page in centimeters. 1 inch = 2.54 centimeters. Use the conversion table below to convert our paper dimensions from inches to centimeters. Calculate the area of the page using metric values.
Width:
8.5 in
X
2.54cm
=
21.6cm
1 in
Length:
11 in
X
2.54 cm
=
27.9cm
1 in
Length of our paper:
27.9cm
Width of our paper:
21.6cm
Area of a piece of paper (Area = Width x Length):
60.3c
m2
Questions:
1. What are some potential sources of error when making measurements?
Some of the error sources can be instrumental,environmental,procedural,and human. All of these errors can be how they affect the results.
2. Why is it important for all scientists to use a standard system of measurements?
It is important that other scientists can understand and replicate the same measurements so that it is true for everyone.
III. MEASURING VOLUME
Volume is the space occupied by an object. Units of volume are usually cubed units of length, but can also be expressed as divisions/multiples of a liter, i.e., 1L = 1000 c
m3
= 1000 mL.
In scientific laboratories, volume is measured using pipettes, beakers and graduated cylinders. In general, pipettes are used to measure small volumes (≤ 25 mL), while larger volumes (≥ 25 mL) are measured with graduated cylinders.
When liquid is in a container, the liquid may “respond” to its container and create a curve. This curve is called a meniscus. When reading the scale on the side of a container (e.g. a graduated cylinder), you must account for the meniscus. To properly read the measurement, hold the container level with the meniscus at eye level and read the value at the bottom of the curve.
1. Look at the image to the left of water in a graduated cylinder with units in mL. Record the volume of water in the space provided below. Assume the graduated cylinder is level and at eye level.
36 mL
IV. Mass, Volume, and
Density
Water displacement can be used to measure the volume of a solid object. The following exercise will demonstrate this process.
Once the virtual lab is loaded, you should see a pool of water and a wooden block. You should also be able to see the mass and volume of the block (which you can change using the sliders), and you should be able to see the density. Finally, you should be able to see where you can change the material the block is made of. Let’s start by changing the material to aluminum.
1. What is the density of the aluminum block?
2.70 kg/L
2. (i) As you increase / decrease the volume of the aluminum block, what happens to its mass? (
ii
) What happens to the volume when you increase / decrease the mass? (
iii
) What does this tell you about the relationship between volume and mass of an object?
i
as the mass increases the volume of the aluminum increases as well.
ii
as you increase the mass of the aluminum the volume of the water increases as well.
iii
as the mass increases/decreases the volume will increase/decrease.
1. (i) Now, instead of using an aluminum block, select “My Block”. (i) How does the density of “My Block” change in response to increasing and decreasing mass? (ii) How does the density of “My Block” change in response to increasing and decreasing volume? (iii) What does this tell you about the relationships between mass, volume, and density?
i
If we increase the mass, then the density will also increase
ii
If we increase the volume the density decreases, if we decrease the volume then the density increases
iii
mass is how heavy something is, volume tells how big it is, and density is mass divided by volume.
3. Now, set the material back to aluminum. Using your mouse, pick up and drop the aluminum block into the pool of water. Record the volume of the pool while the block (i) is in the pool, and when the block (ii) is not in the pool. (iii) How much water does the aluminum block displace? (iv) What does the amount of water displacement tell you about the aluminum block?
i
10
5.00 L
ii
100.00 L
iii
5.00 L
iv
The amount of water displacement tells you the volume of the aluminum block
We just determined that mass and volume of a material are related in such a way that increasing or decreasing one causes a respective increase or decrease in the other. Let’s change the material of the block back to wood to gain more insight on this relationship, and their relationship with density.
1. Change the block material to wood.
2. Change the mass of the wood to 2.00 kg (you can manually type in the mass). What is the volume?
5.00 L
3. (i) How does the volume change if you double the mass of the wooden block to 4.00kg? (ii)What does this tell you about the relationship between mass and volume of a material?
i
It doubles the volume to10.00L.
ii
the volume of the object is proportional to its mass.
4. How does the density change if you double the mass of the wooden block from 2.00kg to 4.00kg?
The density remains the same as you change it from 2.00kg to 4.00kg
5. Using your mouse, drag and drop the wooden block into the pool of water. What happens?
The wooden block floats inside the pool of water
6. How much water does the wooden block displace?
It displaces 2L
7. What does the amount of water displacement tell you about the wooden block?
It has less density than the other block.
8. What do you think explains the different behavior of wood and aluminum in water?
Both objects have different densities compared to the water, higher density will sink, lower density will float.
SUMMARY: Based on these findings, we could say that a material has a constant, unchanging density. In fact, density of materials is such a constant that we use it as a defining characteristic to help identify different materials. And since the density of a material is an unchanging value, changes in volume or mass of that material must occur in relation to one-another such that density remains constant. In other words, a tiny tree branch will always float on the surface of a large lake, just as a large tree trunk will float in a swimming pool because, even though the mass and volume of the wood and water change, they always change equally so that the density of each material remains the same. This allows us to develop the following formula relating (D)ensity, (M)ass, and (V)olume to one another:
D = M/V
Using this equation, if we know the enough about the material, we can always calculate what we do not know. For example:
1. On your web page in the upper right-hand corner, you can change the experiment to different types of blocks. Change the experiment to “Mystery.”
Using the scale and pool of water, calculate the density of Block A and Block E.
Mass
Volume
Density
Block A:
65.14 kg
3.38 L
19.3 kg/L
Block E:
3.53 kg
1.00 L
3.53 kg/L
2. If you know the density of an object is 3.75 kg/L, and you see that it displaces 1.50 L of water, how much mass does the object have?
5.63 kg
3. If you know an object has a density 0.33 kg/L, and you see that it displaces 5 L of water, (i) how much mass does the object have? (ii) How much volume does the object have?
i
1.65 kg
ii
5L
V. MEASURING TEMPERATURE
Temperature is the amount of heat present in a particular substance, and it is recorded in degrees Celsius (oC). The Celsius scale is based on water freezing at 0 oC and boiling at 100 oC. To convert between Fahrenheit and Celsius the following equations are used:
F = C (1.8) + 32 or C = (F – 32) /1.8
Using the internet, determine today’s sea surface temperature for San Francisco Bay, California in Fahrenheit. Using the formula above, calculate what that temperature is in Celsius. Do the same thing for the city of San Francisco. Record your answers below in Table 6.
Microscopes are tools used to examine specimens too small to be observed with the naked eye. There are two types of microscopes that you will use in this lab, compound light and dissecting microscopes. In general, a compound light microscope is used to visualize very small items (e.g. blood cells) while a dissecting microscope is used for observing much larger items (e.g. mouthparts of a grasshopper).
A. Familiarize yourself with the use of the light microscope
1. Navigate to the following website, which will simulate using a compound microscope
Where you look through to see the specimen. Also helps magnify the image
Arm
Connects to the base and helpful for carrying the microscope
Coarse Focus Adjustment
Moves the stage up and down to bring the image into focus
Fine Focus Adjustment
Part of the coarse adjustment, brings the image into sharp focus
3. Follow the voice-guided tutorial to familiarize yourself with the microscope controls and view options.
Questions:
a. View the letter e slide under the scope.
b. (i) Draw the letter e below as you view it through the microscope with the lowest power objective. (ii) As you view the letter e, how is it oriented? Upside down or right side up? (iii) What does that tell you about how the microscope processes the image?
i
e
How to draw: Place your cursor in the cell to the left. Click on Insert>Drawing>+New>Select Line>Scribble. Now draw what you see with your mouse. When done choose save and close.
ii
is oriented upside down
iii
they process the image like a mirror, you see the image is flipped.
c. Observe how the image moves when the slide is moved to the left or right.
when the image moves to the right when the slide moves to the left and vice versa.
d. What happens to the brightness of the view when you switch from the 4X to the 10X objective?
The brightness gets brighter.
B.
Magnification
1. Examine your microscope. (i) What do the numbers on the objectives mean? Assume that you see the number 10x on your oculars. (ii) What do you think that means?
i
ii
2. Calculate the total magnification (objective magnification x ocular magnification) for each objective (4x-40x) and record in Table 8 below.
Table 8.
Objective Magnification
Ocular Magnification
Total Magnification
4 X
10 X
40 X
10 X
10 X
100 X
40 X
10 X
400 X
Questions:
a. How many times is the image of the e magnified when it is viewed through the highest power objective lens?
10 X, was the objective used to be able to see clearly the “e” image.
b. If you didn’t know what you had on your slide (an e) and you began examining it at the highest power, how could you determine it was an e?
First, start from the lowest magnification and increase the magnification until you are able to see the image clearly.
C. Field of View
The field of view is the area you can see when you look through the lens of a microscope (Fig. 5). Understanding the size of this field under different magnifications is important because it allows you to estimate the size of objects in your view. The following procedure demonstrates the determination of field of view (FOV) under various magnifications.
Procedure:
1. Click on the “Try this” button, and then select the “m1” slide.
Figure 5: Field of view under various magnifications
2. Following the instructions, try to calculate the height of the e from top to bottom.
150 micrometer
3. Follow the similar instructions for the m2 and m3 slides.
m2
8 micrometer
m3
2 micrometer
Questions:
a. Discuss the advantage and limitation of viewing specimens under highest magnification.
Advantage
An increase in detail can be viewed
Disadvantage
Less of the slide is able to be seen
b. What about the low-power objective?
Advantage
Covers a wide field of view
Disadvantage
Smaller parts of a specimen cannot be fully viewed
D. DEPTH OF FIELD
The depth of field is the difference in distance of the nearest object in focus on a plane and the furthest object in focus on a plane. The following procedure will demonstrate how to use the microscope to determine the depth of the field of view.
1. Navigate to
2. (i) As the instructor adjusts the focus, what do you notice about the strings in view? (ii) Can you identify the order that the strings are layered from top to bottom?
i
the focus can only focus on one string at a time.
ii
blue, red, yellow
Questions:
a. How does depth of field affect viewing specimens that are thick?
The depth of field allows us to study properly microscopic structures in three dimensional ways.
b. (i) Are all three threads visible under the low power? (ii) Can they all be seen at the same time under higher power?
i
low power
provides the greatest depth of field.
ii
no,because of the narrow depth field.
c. Which objective provides the greatest depth of field?
low power
E. Preparing Wet Mounts of Biological Specimens
1. Navigate to
. Take note how the instructor prepares a slide for viewing under the microscope. This prepared slide is called a wet mount
MICROSCOPE TIPS:
This is an air bubble, NOT your specimenThese are cotton fibers, not your specimen
2. Next, navigate to
. (i) As you watch the video, note the diversity of organisms you see. As you observe the microorganisms, (ii) why do parts of some of them move in and out of focus, while other parts remain in focus?
i
ii
F. Dissecting Microscope
1. Navigate to
https://www.youtube.com/watch?v=JNCeBBwfb_0
2. Observe the demonstration on how to use a dissection microscope.
3. What are some major differences between compound microscopes and dissection microscopes?
dissection microscope is used to watch living organism. while compound is used to see dead organism or bacterias.
4. When would you use a dissection scope instead of a compound microscope?
RAN OUT OF TIME HERE .
Ocular Lens
Zoom
Magnification Adjustment
Arm
Focus
Adjustment
Transmitted Light Source
Stage
Base
Figure 6. Major parts of a dissecting microscope
G. Comparison of Compound and Dissecting Microscopes
Compare the two types of microscopes we examined today in Table 9.
Table 9:
Characteristic
Dissecting Microscope
Light Microscope
Magnification
Resolution
Size of field of view
Depth of field
Orientation of Specimen (Letter e’s)
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