Tiny Particles
Learning Objectives
Students will be able to:
- Explain that tiny particles called "particulate matter" float in the air
- Compare sizes of PM10 and PM2.5 particles to familiar objects
- Describe where particles in air come from
- Explain why smaller particles can be more harmful
The Big Question
"What else is floating in the air besides gases?"
Opening: Dust in the Light (5 minutes)
Have you ever seen this? When sunlight comes through a window, you can see tiny specks floating in the air. Those specks are always there - you just can't see them without the light!
Those floating specks are called particles or particulate matter. Scientists call them "PM" for short. Some particles are big enough to see, but many are way too small!
What is Particulate Matter (PM)?
Particulate Matter (PM) = tiny bits of solid stuff or liquid droplets floating in the air
These particles come from many sources:
- Dust from roads, construction, and soil
- Smoke from fires, cooking, and candles
- Pollen from plants
- Car and truck exhaust
- Factories and power plants
Two Important Sizes: PM10 and PM2.5
Scientists measure particles in micrometers (also called microns). A micrometer is SUPER tiny - 1,000 micrometers fit in just 1 millimeter!
| Type | Size | What's It Like? |
|---|---|---|
| PM10 | 10 micrometers or smaller | Like dust you can sometimes see. Can get into your nose and throat. |
| PM2.5 | 2.5 micrometers or smaller | WAY smaller than PM10! Too small to see. Can get deep into your lungs. |
How Small is That? Size Comparisons!
Let's compare sizes:
| Object | Size | Comparison |
|---|---|---|
| Human hair | 70 micrometers wide | You can easily see this! |
| Grain of sand | 90 micrometers | Bigger than a hair |
| PM10 | 10 micrometers | 7 PM10 particles lined up = 1 hair width |
| PM2.5 | 2.5 micrometers | 28 PM2.5 particles lined up = 1 hair width |
Activity: Human Hair Comparison (15 minutes)
Materials:
- Piece of paper
- Pencil and ruler
- Colored pencils
Steps:
- Draw a line 7 centimeters long - this represents a human hair (scaled up)
- Divide the line into 7 equal parts (each 1 cm) - each part represents 10 micrometers
- Color ONE part yellow and label it "PM10" - this is how big a PM10 particle is compared to a hair
- Now divide that one part into 4 smaller pieces - each piece is 2.5 micrometers
- Color ONE of those tiny pieces red and label it "PM2.5" - this shows how tiny PM2.5 really is!
Why Do Smaller Particles Matter More?
Bigger Particles (PM10)
- Can get into your nose and throat
- Your body can often catch them
- You might sneeze or cough them out
- Nose hairs help trap them!
Smaller Particles (PM2.5)
- So tiny they slip past your nose
- Can travel deep into your lungs
- Can even get into your blood!
- Harder for your body to get rid of
Think About It Like a Net
Imagine your nose and throat are like a net trying to catch particles. Big particles get caught in the net. But tiny PM2.5 particles are so small they slip right through the holes!
Where Do Particles Come From?
Outdoors
- Cars and trucks
- Wildfires
- Dust from roads
- Factories
- Pollen from plants
Indoors
- Cooking (especially frying!)
- Candles and incense
- Fireplaces
- Dust from cleaning
- Pets
Science Notebook (10 minutes)
Draw and answer:
- Draw a picture comparing the size of a human hair, PM10, and PM2.5
- Answer: Why are PM2.5 particles more dangerous than PM10 particles?
- List 3 sources of particles that might be in your home
Key Takeaways
- Air contains tiny floating bits called particulate matter (PM)
- PM10 particles are 10 micrometers - like fine dust
- PM2.5 particles are 2.5 micrometers - too tiny to see!
- Smaller particles can get deeper into our lungs
- Particles come from cooking, cars, fires, dust, and more
Vocabulary Words
Particulate Matter (PM)
Tiny solid pieces or liquid droplets floating in the air.
Micrometer (micron)
A tiny unit of measurement. 1,000 micrometers = 1 millimeter.
PM10
Particles 10 micrometers or smaller. Can enter nose and throat.
PM2.5
Particles 2.5 micrometers or smaller. Can enter deep into lungs.