Experiment & Learn (part 1)

30 Sep 2016

Experiment and Learn (part 1)

Abstract concepts can be challenging to explain to students. What better way to grasp these concepts than getting down to doing it? Have your students try out these hands-on activities and explore learning by doing. The fun experiments will not only engage your students but will also help them apply concepts to their daily life.

Water Purification: For Primary Levels


Water is one of the most important and precious resources on earth, central to our society’s survival and well-being. To meet the increasing demands of a growing population, the need for clean water is becoming ever more essential and different types of water purification systems are in place to ensure this. One example is water filtration – a system which can range from that in a home-based water dispenser, or that of an industrial treatment plant serving the needs of many.

Try this simple experiment with your pupils to understand how basic water purification works and discuss issues related to water and water sustainability with them.

photo credit: http://tryscience.org/nld/handson2.html
  • Half or one litre plastic bottle
  • Scissors or box cutter
  • Sand
  • Small rocks/gravel
  • Coffee filter
  • Activated carbon (from a pet store)
  • Plastic cups
  • Water
  • Food colouring


  1. Using a pair of scissors or a box cutter, cut the top off a half or one liter plastic soda bottle, about 3/4 the way up from the base of the bottle.
  2. Create a "materials" table with sand, rocks, activated carbon and coffee filters.
  3. Now, divide pupils into design teams, or if enough materials are available, have pupils gather one of each of the following materials: a cup of sand, a cup of activated carbon, 1/2 cup of rocks/gravel, coffee filter and plastic bottle pieces.
  4. Next, instruct pupils to create the main structure of their filter. Invert the top plastic bottle piece to form a funnel into the remaining bottle, which will now serve as a reservoir or basin for water to collect. The top portion will act as a funnel for filtering your sample wastewater.
  5. Using a coffee filter, instruct pupils to place this in their makeshift funnel’s top portion. Now have each team construct layers using the sand, rocks or gravel, and activated carbon that will make up their filter.
  6. Now that each group has their filters completed, experiment with how effective each group’s designs are.
  7. Add food colouring to the water to simulate wastewater.
  8. Now line up each group's water filter. Help pupils slowly trickle this mock wastewater through their filter to see how effective their designs turned out to be. Use a stopwatch to see how fast water trickles through and compare the reservoirs to see how effectively materials were filtered out.


Water purification is the removal of contaminants from raw water to produce drinking water that is pure enough for human consumption or industrial use.

For the purpose of this experiment, an optimal filter would comprise a ½ inch layer of activated carbon, then sand and finally some rock or gravel bits at the top of the filter.

This is a gravity-fed filtration system using percolation. In this kind of system, particle size is key. A well-functioning filter would have larger particles (gravel, rocks) on the top of the funnel filtration system with smaller particles (sand and activated carbon) towards the bottom.

This is so larger materials like dirt, leaves and other organic matter can be filtered out first, allowing water to pass through to the activated carbon layer where naturally charged ions are able to grab smaller particles one can only see with a microscope. The coffee filter serves as a final membrane to collect wastewater constituents that have been filtered. A good result would be a water filter that slowly lets water pass through, with larger particles gathered on top and smaller particles caught in the lower levels of the filter system.

Most of the food colouring should be filtered out and the water should look relatively clear. Most modern watewater treatment systems use similar methods comprising a large screen to filter large items, then brought down to holding tanks where solids and liquids are separated. Solids are dried and sent to a landfill, and the remaining liquids are pushed through membranes and other media to extract finer particles.




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