Water Filter (one volunteer)
Supplies needed:
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Clear plastic 2-liter bottle(s) – depending on how many filters you want to have
Playground or paver sand
Gravel
Any other materials you want to add to your filter – some examples:
o Cotton balls or batting
o Sponges
o Cloth
o Charcoal / carbon
Coffee filters
Rubber bands
Pitcher of water
Clear plastic cups (8-12oz)
Plastic spoons
Materials to make water dirty – some examples:
o Potting soil
o Vegetable oil
o Food coloring or tempera paint
o Dry oatmeal
o Leaves or pine straw
Sink access to rinse filter between uses
Procedure:
1. Before competition day, build your filter(s):
a. Cut the top off the 2-liter bottle, an inch or so below where the sides of the
bottle start to curve toward the opening.
b. Put a piece of coffee filter over the bottle opening and use a rubber band to
secure it tightly in place. Trim excess paper if necessary so the paper is not
covering too much of the bottle.
c. Turn the top piece of the bottle upside down and place it in the bottom part of
the bottle (like a funnel).
d. Add different materials to your filter one layer at a time until the funnel part is
about ¾ full. Store and transport the filters carefully so the filtration media don’t
spill out.
**Having more than one filter will allow more students to do this activity at once
2. On competition day, set the filters up on a table with the various contaminants (soil,
food coloring, etc). Prime the filters by pouring clean water through them to rinse dust
from the sand and gravel. Empty the bottom part of the filter and rinse. Repeat if
necessary til the water runs clear.
3. Give the students a cup of water and a plastic spoon and allow them to add
“contaminants” to their water – they do not have to add all of them. Remind them not
to go overboard (a little food coloring goes a long way).
4. Once their water is dirty, let the students pour their water through the filter and
observe the results. Ask them what other materials they might use if they were building
a filter.
5. Empty out the filtered water and rinse the bottom section of the bottle before the next
students use it.