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Pollution science lab midterm
Terms in this set (52)
"Dry soil" typically has been dried how???
Dried in an oven
What 3 apparatuses were used in our soil lab
• Electric oven with thermostat
• Balance (or called scale)
How do you calculate soil moisture content %?
Soil moisture content (%) =
[(wet soil (g) - dry soil (g))/dry soil (g)]
what were our 3 known weights when weighing out our soil sample?
1. Metal can
2. Metal can + wet soil
3. Metal can + dry soil
What is the soil particle size range for sand?
Sand, 2 - 0.05 mm
What is the soil particle size range for silt?
Silt, 0.05 - 0.002 mm
What is the soil particle size range for clay?
Clay, <0.002 mm
how does the hydrometer method work?
The hydrometer method of silt and clay measurement relies on the effect of particle size on the differential settling velocities within a water column.
What apparatuses are needed to perform the hydrometer method test?
• Soil dispersing stirrer: A electric stirrer, or shaking in a closed container.
• Hydrometer with Bouyoucos scale in g/L
• Dispensing solution: dissolve 20 g Sodium Hexametaphosphate [(NaPO3)13] in 0.5-L water
describe the procedure for the hydrometer method
1. Weigh 40 g dry soil (2-mm) into a 500-mL bottle, add 300 mL water.
2. Add 60-mL dispersing solution.
3. Transfer the mixture into a blender.
4. Cap the blender and blend for half a minute.
5. Transfer suspension quantitatively into a 1-L calibrated cylinder (hydrometer jar), and bring to volume (1 L) with water.
how to determine blank with hydrometer method
• Dilute 60 mL dispersing solution to 1-L hydrometer jar with water.
• Mix well, and insert hydrometer, and take hydrometer reading, Rb
how to determine percent of silt and clay with hydrometer method
• Mix suspension in the hydrometer jar, using a paddle carefully, withdraw the paddle, and immediately insert the hydrometer.
• Take hydrometer reading 40 seconds after withdrawing the paddle. This gives reading, Rsc
what equation is used to determine silt and clay percentages
[silt + clay] % = (Rsc-Rb)x100/dry soil (g)
how did we determine percentage of clay
• After 8 hours, insert the hydrometer, and take hydrometer reading, Rc
Clay %= (Rc-Rb) x 100/dry soil (g)
how did we determine percentage of sand
Sand % = 100 - [silt + clay] %
Teachers are interested in more __________
explanations than workplace audiences,
which are more interested in results.
when writing a lab report, what aspects of the scientific method need to be considered?
4.) And carefully drawn conclusions based on sufficient data. Data must be presented clearly, much of it in visuals such as tables and graphs.
Data must be __________ and __________.
Try placing your notes
into this 4 part format:
1.) Materials used
2.) Method followed
3.) Results seen
4.) Conclusions drawn
True or False
When you keep your own notes, it is
important that you record the same
type of data every time you record
4 things to include when using other research to help in your own
1.) The information
2.) Whether the information is a direct quote or not
3.) The source of the information
4.) The subject matter of the
what 5 questions should be answered with every lab report?
1.) What was the purpose of the lab?
2.) What materials were used?
3.) What was the procedure?
4.) What were the results?
5.) What are the conclusions?
A lab report should include what 4 parts?
1.) I. Introduction
2.) II. Materials and Procedure
(also called Experimental Section, Methodology,
3.) III. Results and Discussion
4.) IV. Conclusions
what should be in the materials and methods section
1.) ALWAYS describes the materials or instruments used
2.) ALWAYS describes the procedure used, including relevant calculations
3.) ALWAYS uses chronological order (through time)
what should be in the results and discussion section
1.) ALWAYS presents test results
here, usually includes
accompanying visuals - tables,
2.) ALWAYS discusses the results,
explains why things happened,
tells what is significant
3.) USUALLY uses chronological
order for results seen and causeto-
True or False
the results and discussion can be divided into two parts
what should be in the conclusion section
1.) ALWAYS includes a brief summary that tells how the test results, findings, and analysis meet the objectives established at the beginning of the report.
2.) SOMETIMES uses chronological order;
3.) SOMETIMES uses priority order.
what 4 additional sections could possibly be included in a lab report
1.) Theory section - Explains the scientific theory behind
2.) Calculations section - if the labs used involve
3.) Recommendation section - comes after the
conclusion and used if necessary for the lab
4.) Appendix section - separate section at the end of the
report, that contains tables and graphs whose
complexity and length disrupt the flow of the report
Scientific exploration explores
according to basic __________
and __________ reasoning
called the scientific method.
The scientific method is
responsible for the structure
of the lab report.
what is an experiment
Experiments are the controlled
observations of what occurs
naturally. After a series of
experiments, an experimenter
may see a pattern emerging.
what is a hypothesis
a tentative explanation that helps
organize knowledge and predict
difference between a result and a conclusion
A result is simply what happened; a conclusion goes beyond what
happened. A conclusion requires a scientist to draw an inference, to make a point about the results.
what is objectivity
Objectivity is an important concept in scientific thinking. Objectivity means that the conclusion reached is based on facts and not a whim or bias. It also means that another experimenter can follow the same procedure and come out with the same results
how do objective knowledge and subjective knowledge differ?
Objective knowledge is different from subjective knowledge. Subjective knowledge, based on personal opinion, is difficult to measure and can vary from one person to another
what is passive voice and why is it used in lab reports?
Because objectivity is important, lab reports often make use of passive voice. Passive voice uses a form of the verb "to be" plus the past participle of the verb. Use of passive voice keeps the reader focused on the process, instead of on the scientist performing that process
How do you write chemical formulas in lab reports
Al2O3, (aluminum oxide), NaCl (sodium chloride)
how to write math formulas in a lab report
y = ax2 + bx + c
what is an abstract
An ABSTRACT is functioning just
like a baby version of your report. Including:
Materials and Methods
Results and Discussion
what type of analysis is performed by a photo spectrometer?
two limitations of Lambert-Beer's Law
1.) Deviations in absorptivity coefficients
2.) Scattering of light
what two parts does a spectrophotometer consist of
1.) spectrometer for producing light of any selectedcolor (wavelength),
2.) photometer for measuring the intensity light.
describe the structure of a spectrophotometer
what two things make a good light source
as large of a color range as possible
Ideally you would pass light of exactly the right wavelength, __________, for the compound of interest through the cell
what is the importance of using λmax
- Increased Sensitivity
- We get a much larger absorbance reading even though exactly the same amount of light has been absorbed
- By making more specific to the λmax, we have improved sensitivity
what is an Absorption Cell
- Sample compartment
- Receptacle for Sample - 1cm pathwidth
what are the two types of Type of UV/VIS Spectrophotometer
1.) single-beam UV-Vis spectrophotometer
2.) dual-beam UV-Vis spectrophotometer
diagram a single-beam UV-Vis spectrophotometer
diagram a dual-beam UV-Vis spectrophotometer
why use a single-beam UV-Vis spectrophotometer
Most of the known analysis, the wavelength has been determined.
why use a dual-beam UV-Vis spectrophotometer
More easier to scan a range of wavelength vs absorbance to determine the optimum wavelength for a unknown analysis
5 things to keep in mind about UV/Vis spectroscopy
1.) Molecules absorb light in the UV and visible regions of the electromagnetic spectrum
2.) Results in electronic transitions
3.) Compounds with extended system of alternating double and single bonds will absorb UV light
4.) Anything with color absorbs visible light
5.) UV-vis spectroscopy is applicable to a wide range of samples
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