Which filter makes muddy water clearest?
- 👶 Small parts
- 🧼 Wash your hands after
- 💧 Water
- 🧽 A bit messy
My hypothesis
If I change what the filter is made of, then how many lines of print you can read through the filtered water will ______, because ______.
You fill in the blanks. Think about the gaps in each filter, and which gaps are small enough to catch tiny bits of soil. A guess is a good because: the test finds out.
Change, measure, keep the same
CHANGE
what the filter is made of: Sand, Gravel, Cotton balls
MEASURE
how many lines of print you can read through the filtered water, in lines read, of 10
KEEP THE SAME
- the same muddy water, stirred before every pour
- the same amount of filter, filling the cup halfway
- half a cup poured slowly each time
Scientists call the thing you change the independent variable and the thing you measure the dependent variable. The things you keep the same are the controls: if one of them changed too, you wouldn't know which change made the difference. Try each of the 3 levels 3 times.
What you need
- Soil dug from the garden or yard: 3 tablespoons
- Water from the tap: about 6 cups
- Sand (from a sandbox, or play sand): about 3 cups
- Small pebbles or gravel, rinsed: about 3 cups
- Cotton balls: about 12
- Paper cups with a hole poked in the bottom: 3
- Clear plastic cups, all the same size: 3
- A measuring cup
- Measuring spoons
- A spoon
- Paper
- Crayons or markers
Steps
- Print the word SEE on ten lines of a sheet of paper, making it a bit smaller on each line.
- Stir 3 tablespoons of garden soil into 4 cups of tap water to make muddy water.
- Never drink the muddy water, or any water that has been through a filter.
- Rest a paper cup with a hole in its bottom on top of a clear cup.
- Fill the paper cup halfway with sand, gravel or cotton balls: one kind for each filter.
- Stir the muddy water, then pour half a cup slowly through the filter.
- Wait until it stops dripping. That can take a few minutes.
- Stand the clear cup on your sheet and look straight down through the water.
- Count the lines of SEE you can still read, and write the number in your table.
- Rinse the sand and gravel, use new cotton balls, and test each filter two more times.
- Wash your hands after touching the soil.
- Find the mean for each filter, and draw a bar graph.
Every step is one you can do yourself, with a grown-up nearby. Write each number down straight away, in the table below, so nothing is lost.
Your results table
Name ______________________ Fair day ____________
Question: Which filter makes muddy water clearest?
I changed: Filter I measured: how many lines of print you can read through the filtered water (lines read, of 10)
| Filter | Try 1 (lines read, of 10) | Try 2 (lines read, of 10) | Try 3 (lines read, of 10) | Mean |
|---|---|---|---|---|
| Sand | ||||
| Gravel | ||||
| Cotton balls |
MY GRAPH (a bar graph: filter along the bottom, lines read, of 10 up the side)
What I noticed: ______________________________________________
From 4th grade, add the tries for each level and divide by how many there were: that's the mean, and it goes in the last column. Then draw a bar graph, one bar for each thing you tried.
Name ______________________ Fair day ____________
Question: Which filter makes muddy water clearest?
If I change what the filter is made of, then how many lines of print you can read through the filtered water will ________________, because _____________________________________________
| I CHANGE | I MEASURE | I KEEP THE SAME |
|---|---|---|
| Filter: Sand, Gravel, Cotton balls | how many lines of print you can read through the filtered water (lines read, of 10) |
|
What I think will happen, in my own words:
Name ______________________ Fair day ____________
Question: Which filter makes muddy water clearest?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Which filter makes muddy water clearest?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Which filter makes muddy water clearest?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Which filter makes muddy water clearest?
My hypothesis was ☐ right ☐ partly right ☐ not right.
I know because my numbers show:
What surprised me, or what might have gone wrong (7th and up):
Next time I would test:
Idea: Change a second thing: stack two layers, sand on top of gravel and then gravel on top of sand, and compare the lines read.
Why it works
Muddy water is full of tiny bits of soil, and a filter catches a bit when it is bigger than the gaps the water squeezes through. A filter with smaller gaps usually catches more, so its water looks clearer and you can read more lines through it. Even water that looks clear can hold things you cannot see, so filtered water is never for drinking.
Going further (7th and up): Change a second thing: stack two layers, sand on top of gravel and then gravel on top of sand, and compare the lines read.
Board layout
- ❓ Question (10 × 8 in): Which filter makes muddy water clearest?
- 💭 Hypothesis (10 × 9 in): If I change what the filter is made of, then how many lines of print you can read through the filtered water will ______, because ______.
- 🧺 Materials (10 × 12 in): 12 things: see your list.
- 🪜 Steps (22 × 9 in): 12 steps, three tries at each level.
- 📊 Results (22 × 16 in): Your table (Filter down the side, tries across) and your bar graph.
- ✅ Conclusion (10 × 14 in): My hypothesis was right / partly right / not right. I know because…
Materials to list: Soil dug from the garden or yard; Water from the tap; Sand (from a sandbox, or play sand); Small pebbles or gravel, rinsed; Cotton balls; Paper cups with a hole poked in the bottom; Clear plastic cups, all the same size; A measuring cup; Measuring spoons; A spoon; Paper; Crayons or markers.
Bring photos or drawings of your test. Nothing wet, hot, powered or alive on the table.
This project at your grade
| 4th–6th grade | Tries: three at each level. The table: units in the header and a mean column. The graph: a bar graph, or a line for a number that grows. The conclusion: right, partly or not, and the numbers that show it. |
|---|---|
| 7th grade and up | Tries: three or more at each level. The table: a mean for every level of both tests. The graph: a graph with two lines or two sets of bars. The conclusion: the numbers, what might have gone wrong, and a next question. Second variable: stack two layers, sand on top of gravel and then gravel on top of sand, and compare the lines read. |
Every grade this project fits works out a mean. See every project for 4th grade, or print a blank results table.
What a judge will ask
- What did you change, and what did you measure? I changed what the filter is made of and measured how many lines of print you can read through the filtered water, in lines read, of 10.
- What did you keep the same, and why does that matter? I kept the same muddy water, stirred before every pour and the same amount of filter, filling the cup halfway the same, so the only difference was what the filter is made of.
- How many times did you test it? 3 times at each of my 3 levels.
- If you did it again, what would you change or test next? I'd stack two layers, sand on top of gravel and then gravel on top of sand, and compare the lines read.
Make it yours
Keep this project on this device and Peabody counts down to your fair day, with a plan for each day. Nothing is sent anywhere.
Try next
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