Particle Investigation Lab
Learning Objectives
Students will be able to:
- Collect and compare particle samples from different locations
- Analyze collected particles using observation techniques
- Draw evidence-based conclusions about particle sources
- Present findings with supporting data
Lab Overview
In this lab, you'll become a particle detective! You'll collect samples from different locations, observe what you find, and draw conclusions about where particles come from and how they vary by location.
Materials (Per Group)
For Collection
- 4-6 glass microscope slides (or clear tape on index cards)
- Petroleum jelly (thin coating for particle capture)
- Cotton swabs for applying petroleum jelly
- Labels/markers
- Data recording sheet
For Analysis
- Hand lenses or magnifying glasses
- Microscope (if available)
- Flashlight (for side-lighting)
- Comparison chart (provided below)
Procedure
Part 1: Preparation (5 min)
- Apply a thin, even layer of petroleum jelly to each slide
- Label each slide with location name and group name
- Handle slides by edges only!
Part 2: Collection (20 min)
- Place slides at different locations around the school:
- Classroom (on a desk or shelf)
- Hallway (high traffic area)
- Near a window (outdoor influence)
- Near the cafeteria/kitchen
- Gym or outdoor area
- Any other interesting location
- Leave slides for 15-20 minutes (longer = more particles)
- Record exact location and time for each slide
Part 3: Collection (5 min)
- Carefully collect each slide
- Keep slides flat and protected
- Return to lab area for analysis
Part 4: Analysis (15 min)
- Observe each slide under magnification
- Count particles in a standard area (e.g., 1 cm × 1 cm square)
- Describe particle characteristics (size, shape, color)
- Compare slides from different locations
Data Recording Sheet
| Location | Time Exposed | Particle Count | Description | Likely Sources |
|---|---|---|---|---|
| Sample 1: | ||||
| Sample 2: | ||||
| Sample 3: | ||||
| Sample 4: |
Particle Identification Guide
| What You See | Likely Source |
|---|---|
| Fine gray/black particles | Combustion, exhaust, soot |
| Fibers (various colors) | Clothing, paper, carpet |
| Round yellow/orange particles | Pollen |
| Irregular tan/brown particles | Soil, dust |
| Clear/white crystalline | Salt, mineral dust |
| Flat, irregular flakes | Skin cells, paper fragments |
| Fuzzy clumps | Mold, dust bunnies, pet dander |
Analysis Questions
- Comparison: Which location had the most particles? The least? Why do you think this is?
- Types: Did different locations have different types of particles? What does this tell you about sources?
- Limitations: What can't you see with this method? (Hint: Think about particle size!)
- Predictions: Based on your results, which location would likely have the highest PM2.5? Why?
- Recommendations: If you wanted to improve air quality in the location with the most particles, what would you suggest?
Alternative: The Tape Test
No microscope slides? Try this:
- Use clear packing tape pressed onto different surfaces
- Press tape firmly onto surfaces for 5 seconds
- Place tape sticky-side-down on white paper
- Compare what was collected from different surfaces
Surfaces to try: Desk top, windowsill, floor, vent cover, bookshelf top, computer keyboard
Unit 2 Summary: What We Learned
Aerosol Basics
Aerosols are tiny solid or liquid particles suspended in air. Most are invisible.
Size Categories
PM10 (≤10 μm), PM2.5 (≤2.5 μm), and ultrafine (<0.1 μm). Smaller is more dangerous.
Settling vs. Suspension
Large particles fall quickly; PM2.5 stays airborne for hours; ultrafine floats indefinitely.
Indoor Sources
Cooking, combustion, cleaning, human activity, and outdoor air entering.
Key Takeaway
Particles are everywhere, but they vary by location and source. By collecting and analyzing samples, we can understand what's in our air and where it comes from. This investigation method only captures the LARGE particles—remember that the most health-relevant particles (PM2.5) are too small to see even with magnification. That's why we need air quality sensors!