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Filtration Fact Sheet (Continued)
How to Make a Stack of Bottle Filters (Teacher Preparation)
Illinois
July 2009

Materials

√ 5 empty plastic (16 – 20 oz) bottles
√ Cheesecloth
√ Rubber bands
√ 1+1/2 cup of a type of soil (sandy, clayey, or loamy)
√ permanent marker

 

STEP 1

Two bottles of water side by side with illustration showing where to cut the bottles.

  • Remove bottoms from 4 plastic bottles.

  • With 5th bottle, measure and mark where 1/4 to 1/2 cup of water reaches in the bottle. Cut off top of 5th bottle now.

 

STEP 2

Illustration of bottle top covered and bottom end cut.
  • Cover lid end of all bottles with cheesecloth and attach with a rubber band.

 

STEP 3

water bottle upside down filled soil with a half cup of soil.
  • Fill 3 of the 4 bottles without bottoms with 1/2 cup of sandy, clayey or loamy soil. Be sure to use only one type of soil in each stack of bottle filters.



STEP 4

* Small vertical slits may be cut into the bottom of the bottles to improve fit.

Illustration of where to cut slits into the bottome of the bottles

  • Mount bottles as follows (from top to bottom):

    • bottle with no bottom and no soil,

    • bottles with no bottom with soil (x3),

    • bottle with no top.

 

Answers to Student Handout

  1. If more filters are added to the stack, it will take longer for the water to filter to the bottom. There will be more soil to hold water against gravity as well as additional surface area to interact with the water. The soil will hold more coloring and clean the water better.

  2. If fewer filters are used, it will take less time for water to filter to the bottom. There will be less soil to hold water against gravity, as well as less surface area to interact with the water. The soil will hold less coloring and the water will not be cleaned well.

  3. If water is added more slowly, it will have more time to interact with the soil and will be cleaned better.

  4. If water is added more quickly, it will have less time to interact with the soil and will not be cleaned as well.

  5. If water going into the soil is green and water coming out is yellow, some of the coloring was extracted from the water, but not all of it. This is called preferential absorption.

  6. Answers will vary.

Further Investigations

Now that the experiment is finished, ask your students...
“What does this mean to me and why is this important?”

Answers can range from...
“I should be careful not to spill bad chemicals on the ground” to...
“If I use chemicals I should read and follow the directions on the label.”

Other topics related to soil filtration are:

  • Some chemicals must be applied well before a rain because they need to have contact with plants for a while to work.

  • Some chemicals must seep down into the soil to be effective, and rainfall or irrigation is required to incorporate those chemicals into the soil.

  • The addition of chemicals to soil can improve the overall health of soil, plants, and people.

  • Plants grow better if proper amounts of nutrients are added.

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Download Printable Filtration Packet

A Printed Version of this Filtration packet is available in Adobe Acrobat.

Filtration Fact Sheet with Teacher Prep Sheet and Student Exercise
FiltrationFS_0709.pdf (PDF, 276 kb)

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