Filter fun

This month’s blog is brought to you by Clare Docking, one of our advisory teachers who works with industry and schools in the East of England.

Children love to play with mixtures combining solids and liquids to make something different.  In this activity we take this one step further and use filters to reverse this process and separate out the solid again. This investigation is easy to set up as it involves using everyday household materials for the filtering and uses a simple mixture of flour and water for the solution.  Children will enjoy predicting which filter they think will do the best job of separating out the solid from the liquid and then testing to see if they are right. This activity will prompt them to consider the properties of materials and why some make good filters, and some don’t.

Three, two, one – investigate!

• Children love a challenge, so start the investigation by telling the children that a local bio tech company needs their help to find out which material makes the best filter. You could explain that medicines are grown in solutions and then the ‘solids’ grown need to be separated again afterwards. Brainstorm ideas on everyday filters e.g. colanders, tea strainers,plug hole filters.
• Give the children a choice of filters e.g. kitchen roll, tissue, cotton fabric, J cloth, and a commercially produced filter paper such those for coffee machines. Ask them how they are going to ensure that they test all the different filters so that all conditions are kept the same except for changing the filter used?
• Encourage the children to draw on their own experiences when thinking about the task. Do they think any of the filters might go soggy? Are some of the materials more tightly woven and will this be good or bad for filtering? How much do they pour at once and how do they ensure no spillage? Does it matter if the solution is lumpy? This is a good opportunity to bring in previous learning about how liquids and solids behave and to examine the difference between a ‘solution’ and a ‘suspension’. 
• Once the children have decided on what they need to keep the same for a fair test, they need to consider how they can measure results. How will they measure the success of the filter?  This activity lends itself to a variety of measuring and recording methods.  They could, for example, measure the clarity of the liquid produced, or the amount of flour in the filter. Ask the children to time how long the filtering process takes with each material – how might the time taken by each filter be relevant to the bio-tech company when they decide which filter to use?
• The children will love to report back findings to the class and ultimately the bio-tech company in a variety of ways e.g. videos, reports, letters or photos with captions.

Full details of activity can be found in our free resource and incudes teachers’ notes,

children’s activity sheets and national curriculum links.

 

Top Tips

Here are some tips to make your investigation a success:  

• This activity is perfectly suited for COVID secure working as it can easily be carried individually, in pairs or small bubbles as equipment is inexpensive and easily available.
• Encourage the children to spot mistakes in their own processes and hold mini plenaries to discuss these. For example, is any liquid running down the side of the filter when they pour it?
• Allow plenty of time for the investigation as some of the filters work more slowly than others. While the children are watching and waiting for the filtering to take place, encourage them to record ideas about their testing process on post-its or devise a table to record results.
• If you don’t have any funnels or containers, simply cut the top off a plastic bottle (e.g. bottled water) and in an instant you have the container and funnel (NB. Be aware of sharp edges – cover with tape if necessary).

If you would like to share this activity with children's families, why don't you put a link to this related IndusTRY at home activity on your school website?