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Sampling Particulate Matter
from the Air

Grade Levels: 3-6

Time: 1 hour or so per day for two to three days

Purpose
Demonstrate that small, suspended particles are present in air.

Through sample collection, analysis, and data review, students will gain experience with the scientific observational methods.

Background
Air is not empty space. It is made of matter - mainly different types of gases. The normal composition of air is about 78% nitrogen (N2), 21% oxygen (O2), and 1% other gases such as argon (AR), carbon dioxide (CO2), methane (CH4), and helium (He). The gases are comprised of molecules that are made up of atoms, the fundamental units of matter. Air is essentially a layer of trillions and trillions of gas molecules.

Air also contains solid particles composed of many substances. Many of these particles are too small to observe individually; however, collectively they may contribute to limited visibility and haze in some areas. Air-borne particles are produced form many sources including agricultural lands, diesel engines, cars, electric utility boilers to name a few. Concern has been growing recently regarding the health effects.

Objectives

Students will:

  1. Devise a simple sampling plan.
  2. Collect samples of particles deposited from the air at various locations.
  3. Document the locations and conditions of the samples collected.
  4. Compare collected samples with quality control samples (trip blanks).
  5. Compare samples collected at different locations.
  6. Describe their findings.

Materials

  • Slide projector or overhead projector
  • Extension cord
  • Clear plastic packing tape
  • Cardboard slide frames
  • Scotch tape
  • Thumb tacks
  • 16 penny nails (to hold samplers to ground)
  • Pen/paper
  • Envelopes
  • Field notebook (or sample documentation form included)

Preparation

1. Assemble sample collection media as follows:

a) Punch hole in corner of folded slide frame
nbsp;
b) Write place to record sample name and other relevant sample information.
 
c) Place clean, unused piece of clear plastic packing tape inside slide frame with sticky side up.
 
d) (Option for older students, grades 5-6) For older grades and if additional quantification desired, print grid on plastic overhead with squares of 0.5 centimeter on a side (0.5cm x 0.5 cm = 0.25 cm2).
 
d) Fold slide frame over so as to enclose the piece of clear packing tape. The optional grid described in the previous item should be enclosed in the slide frame at this point for use with older students.
 
e) Secure folded halves of slide frame with piece of scotch tape.
 
f) Carefully place newly prepared sample collection media in clean envelope to prevent contamination.

2. Prepare a field notebook for students to record the following sample specific information (sample documentation form included in printer-friendly MSWord and PDF formats at top of this page).

  • Sample name. Suggest using student name followed by date.
  • Location sample collected.
  • Date sample collected.
  • Name of person who collected sample.
  • Weather conditions during sample collection period.
  • Additional notes

Activity

Sample Collection

1. Develop a simple sampling plan with the students. Attempt if possible to address a question such as whether it's dustier near the school baseball field, black top, grass play area, or indoor classrooms. Alternatively, you may want to let kids collect sample from home, say in their living rooms.

  • Determine where samples will be collected
  • Determine how many samples to collected
  • Determine what time period to sample (ie. single day, several days, whole week etc.).

2. Have students deploy samplers. Two samplers should be used at each location (optional), one to collect a “true” sample, the other to act as a quality control “trip blank” sample. Samplers placed on the ground can be secured through the hole in corner with a 16 penny nail. Samplers may also be taped or stabled to the sides of buildings or fences. Samplers deployed indoors may simply be laid on counter tops and may not need to be secured. Field blank samplers are not removed from their respective envelopes but are left in place next to the true sample so potential contamination during transportation and storage can be assessed.

3. Students should fill out the field notebook forms with all relevant information

4. After the prescribed sampling period, have students collect the samplers by placing them back in the protective storage envelopes. Take care not to press the envelope into the sticky tape of the sampler.

5. Students should update their field notebooks with the ending sample collection date and time.

Sample Analysis

6. The amount of particulate matter collected is determined by viewing the samples with a slide projector or overhead projector. Make sure the slide projector is properly focused.

7. Have students view each sample pair (true sample + field blank), comparing amount of particles in the “true” sample to the amount on the “trip bank.” If the trip blank is dirtier than the true sample, students should conclude that the samples were somehow contaminated during storage or transport and that they should not base any conclusions on the true sample (invalidate the sample).

8. After validating all of the true samples with their corresponding trip blanks, have the students rank all valid samples from cleanest to dirtiest. This does not apply to the field blanks, which only serve to validate the true samples.

9. (Option for older grades, see Preparation) If the optional grid was added to the samplers, have students select one to three squares in each sample.Have students count the number of particles in each square (area of each square is 1/4 cm2).

10. (Option for older grades, see Preparation) For each grid that the students counted the number of particles, have students determine the number of particles per square centimeter as follows (# = number):

Particles per square centimeter (#/cm2) =
(Number of particles / 0.25 cm2) * 4

11. (Option for older grades, see Preparation) If the students counted particles in more than one grid squares per sample, have them determine the average number of particles per square centimeter for each sample as follows (# = number):

(# Particles in first square) + (# Particles in second square) + (# Particles in third square)
(Number of squares counted)

Data Interpretation

12. Have the students compare the samples and identify possible trends or inconsistencies. For instance, sample collected outdoors may be dirtier/cleaner on average than those collected indoors, or samples collected near a dirt lot (baseball diamond) may be dirtier than samples collected near a grass playground.

13. Have students draw conclusions based on their observations of the samples. If the students had attempted to address a question(s), does that data support their initial hypothesis. For example, are the samples collected indoors cleaner than those collected outdoors, or are the samples collected near the baseball diamond dirtier than those collected near the black top or grass play area.

14. (Option for older grades) Have the students prepare a presentation of their project including the following:

  • State their question (if any)
  • State their hypothesis (if any)
  • Simple write-up of their method, procedures and materials.
  • Describe any problems encountered
  • Describe sample locations
  • Prepare a bar chart or similar graphic presenting the number of particles per square centimeter (#/cm2) observed at each sample location.
  • Conclusions (if any)

Science Content Standards for California Public Schools (Adopted 1998)

Grade Three
5. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Student will:

D) Predict the outcome of a simple investigation and compare the result with the prediction.
 
E) Collect data in an investigation and analyze those data to develop logical conclusions.

Grade Four
6. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:

A) Differentiate observation from inference and know scientists' explanations come partly from what they observe and partly from how they interpret their observations.
 
B) Measure and estimate the weight, length, or volume of objects (particle count in this case).
 
C) Formulate and justify predictions based on cause-and-effect relationships.
 
F) Construct and interpret graphs from measurements.

Grade Five
6. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:

B) Develop a testable question.
 
C) Plan and conduct a simple investigation based on a student-developed question and write instructions other can follow to carry out the procedure.
 
D) Identify the dependent and controlled variables in an investigation (in this case, number of particles as a function of sample location).
 
F) Select appropriate tools (e.g., thermometers, meter sticks, balances, and graduated cylinders and make quantitative observations (in this case, particle samplers and slide projector).
 
G) Record data by using appropriate graphic representations (including charts, graphs, and labeled diagrams) and make inferences based on those data.
 
H) Draw conclusions from scientific evidence and indicate whether further information is needed to support a specific conclusion.
 
I) Write a report of an investigation that includes conducting tests, collecting data or examining evidence, and drawing conclusions.

Grade Six
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:

A) Develop a hypothesis.
 
B) Select and use appropriate tools and technology to perform tests, collect data, and display data.
 
C) Construct appropriate graphs from data and develop qualitative statements about the relationships between variables (in this case, particle count vs sample location).
 
D) Communicate the steps and results from an investigation in written reports and oral presentations.
 
E) Recognize whether evidence is consistent with a proposed explanation.