details of the activity can be found in the CIEC publication 'Cough Syrup'
which can be downloaded from http://www.ciec.org.uk/pdfs/resources/cough-syrup.pdf|
The Activity: Filtration
- In the lesson prior to this, children investigate the most effective method of producing the active ingredient for a new cough syrup. They test different conditions for growing yeast.
- In this activity, children are reminded that the active ingredient is a micro-organism which is living in a liquid (growth solution) and they are challenged to suggest ways of getting the active ingredient out of the liquid.
- After a class discussion about different methods, children think about how to test different materials as filters. They use a mixture of flour and water to represent the micro-organism and growth solution.
- Groups might work together to devise a fair test. If using this approach they may find the interactive planning tool a useful resource. Alternatively, each group could be asked to test four different materials to find the most effective filter. In this case, they should place their first chosen material in a funnel or upturned bottle and hold it over a beaker to collect the water. They should stir and then pour 100ml of their flour and water suspension through the filter and time how long it takes to collect 50ml of the liquid that comes through.
- If following instructions, children should repeat this for each of the filters, mixing a new suspension each time.
- Throughout the investigation, children would then compare the times taken as well as the clarity of the filtrate. This may be done by straightforward observation or by placing the filtrate in front of a dark background, shining torch light through the liquid and placing them in order of clarity. Light sensors may also be used for increased accuracy and to produce quantifiable results that can be presented in a bar chart or, if comparing time and clarity, a scatter graph.
- If children have devised their own test, do not be afraid to let them spend time on activities that you know will not work. Also, allow plenty of time at the end of the lesson to discuss and evaluate the methods that they chose. This allows for much deeper learning than if they are guided towards a more ‘successful’ test in the first instance.
- The results of the filtration tests should be reported back to a real or fictitious medicine company and suggestions made about how the active ingredient can be extracted from the filtrate.
Links to the National Curriculum
Y5 Properties and changes of materials:
- use knowledge of solids, liquids and gases to decide how mixtures might be separated, including through filtering and sieving
- demonstrate that dissolving, mixing and changes of state are reversible
- planning different kinds of scientific enquiries to answer questions, including recognising and controlling variable where necessary.
- taking measurements, using a range of scientific equipment, with increasing accuracy and precision
- recording data and results of increasing complexity using scientific diagrams and tables
- reporting and presenting findings from enquiries, including conclusions, in oral and written forms