1
Engage

Filters Catch Things

Duration
30 minutes
Type
Engage
Standards
K-2-ETS1-1, K.CC.A

Learning Goals

Students will be able to:

Big Question

"How can we catch the tiny things in the air?"

Materials Needed

  • Coffee filters (several per group)
  • Clear cups or jars
  • Water with dirt or sand mixed in
  • Water with food coloring (for comparison)
  • Magnifying glasses
  • A real HVAC filter or air purifier filter (to show)

Circle Time: What is a Filter? (5 min)

Teacher Says:

"We learned that tiny things float in the air - dust, pollen, and even germs. How can we catch these things and keep them out of the air we breathe? One way is with a FILTER! A filter has tiny holes that let some things through but catch other things. Today we are going to see how filters work!"

Activity 1: Dirty Water Experiment (12 min)

Steps:

  1. Show students the dirty water (water with sand/dirt)
  2. Ask: "Would you want to drink this water?"
  3. Place a coffee filter over an empty cup
  4. Slowly pour the dirty water through the filter
  5. Look at the water that comes through - it is cleaner!
  6. Look at the filter - see what got caught!
Discovery: "The filter caught the dirt and sand! The water went through, but the big pieces got stuck in the filter. This is how filters clean things!"

Activity 2: Color Water Test (5 min)

Compare:

Now pour colored water (no dirt) through a filter.

  • The color goes right through!
  • The food coloring is too small to catch
Key Point: "Filters catch things bigger than their holes. Very tiny things can still get through. Air filters have very, very tiny holes to catch dust and other small particles!"

Activity 3: Meet an Air Filter (5 min)

Show and Tell:

Show students a real air filter (from a furnace or air purifier).

  • Let them touch it (if clean) - it feels like thick paper
  • Look closely - can you see the tiny holes?
  • Air goes through, but dust gets caught
  • If you have a dirty filter, show how much it caught!
Connection: "Air purifiers use filters like this to catch dust, pollen, and tiny particles from the air. The filter makes the air cleaner to breathe!"

Movement Break: Filter Game (3 min)

Play "Be the Filter":

Choose 2-3 students to be "the filter" - they stand with arms linked
Other students are "air" and "particles"
"Air" students walk through easily (filter lets air through)
"Particles" (carrying pompoms) get caught (filter catches them)

The filter catches the particles but lets the air go through!

Wrap-Up Circle (2 min)

Ask Students:

  • "What does a filter do?" (Catches things!)
  • "What goes through a filter?" (Air and water)
  • "What gets caught?" (Dust, dirt, particles)
  • "How does this help keep air clean?" (Catches dust so we breathe clean air)

Key Takeaway

Filters catch tiny things while letting air or water pass through. Air filters in our homes and schools catch dust and other particles to help keep the air clean for us to breathe!

Teacher Tips

Real Filters

If you can get a clean and a dirty HVAC filter to compare, students love seeing what the filter caught!

Extension

Compare different filter materials - coffee filter vs. paper towel vs. cloth. Which works best?

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