Grade 5
Particles Too Small to See
Matter students cannot see, turned into a number they can plot.
Hold up a jar of algae. It looks like green water. It is not. It is millions of separate living cells, every one far too small to see on its own. You know they are there because of what they do together, and the deeper the green the more of them there are. Drop a Secchi Stick in, measure how far down you can still see it, and something invisible has become a measurement. That is the same reasoning scientists use for atoms.
How the lab meets it
What students do that satisfies the standard
NGSS 5-PS1-1
Standard: Develop a model to describe that matter is made of particles too small to be seen.
What the kit does: Algae is the vehicle. The green is obvious, the cells causing it are not, and a drop under a hand lens settles the argument by showing them discrete and countable. It scales as well: denser culture, deeper green, bigger effect. Brine shrimp sit in the same bag as the contrast case, big enough to see individually from Day 1.
The Secchi Stick
Standard: Turning an invisible cause into a measurement.
What the kit does: Light stops getting through because cells are in the way, and the stick measures exactly how much. Students never need the word attenuation. They infer the invisible from the optical, which is the whole move the standard is asking for, and they do it with the same method oceanographers use off the side of a boat rather than a toy version of one.
Where it goes next
Standard: Not a fifth grade standard, an honest look ahead.
What the kit does: The same reasoning scales straight into the middle school particle model, so a fifth grade class that has done this arrives already holding the idea. Worth knowing if you teach a combined grade or want somewhere to send the students who finish early.
Free downloads
Our Lesson Plans
Each lesson is one Word file. Teacher pages and answer keys first, then the student pages behind the orange PRINT FROM HERE divider.
Millions of Things Too Small to See. Grades 3 to 5
What it covers: Why green water is not green water, and how the Secchi Stick turns something nobody can see into a number on a graph.
How it is built: One Word file. Teacher notes and answer keys up front, then the student pages behind the orange PRINT FROM HERE divider.
Where Did the Salt Go? Grades K to 5
What it covers: Salt disappears into water and the water still tastes of it, so it went somewhere. The second half of the same argument, run on something that is not alive.
How it is built: One Word file. Teacher notes and answer keys up front, then the student pages behind the orange PRINT FROM HERE divider.
Administrator Guide
One guide for the whole elementary program rather than one per lesson. This is the copy to hand a principal or a curriculum director.