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?

Cough Syrup: Thinking like a scientist

Full 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

This publication contains lots of opportunities for children to think and work like a scientist and learn about the different stages in the production of a new medicine. It would be a wonderful way to teach the ‘Properties and changes of materials’ strand of the science curriculum for Year 5, and then extend the topic as well as the full range of enquiry skills with Year 6.  Teachers may choose to approach this lesson in two different ways.  Children can follow fairly prescriptive instructions which give teachers the opportunity to teach and assess skills such as measuring and graphing and the importance of repeat measurements.  Alternatively, teachers can teach and assess children’s skills to plan, carry out and evaluate a fair test by offering children the opportunity to devise and carry out their own investigation.

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. 

Year 5 children carrying out the filtration activity.

Year 5 children carrying out the filtration activity.

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

Working scientifically:

• 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

Cough Syrup: Investigating viscosity

Full details of the activity can be found in the free CIEC resource Cough Syrup which can be down loaded from  http://www.ciec.org.uk/resources/cough-syrup.html

The activities in this resource look at the way a new cough syrup can be developed. Children work to identify the best conditions for growing micro-organisms to produce the active ingredient in the medicine, the best way to collect it, and the ideal consistency for the syrup. Economic and commercial factors are also considered. The activity described here invites children to investigate the effect of altering the ratios of specific ingredients on the viscosity of the resulting syrups. The aim is to find the best consistency for a cough medicine.

The Activity: Viscosity Testing

Resources

• Activity sheet 5 (1 per child, optional)
• 50 ml liquid glucose (available from most supermarkets or pharmacists)
• 50 ml glycerine
• 50 ml water
• 20 ml measuring cylinder                                                                  
• Small containers                                                                                           
• Plastic spoons or stirrers
• Measuring spoons
• Pipettes
• Blank sticky labels

  For the viscosity testing (depending on the test chosen)

• 3-4 marbles
• 1 plastic funnel
• 1 stop clock
• 1 30 cm length of dowel marked in centimetres
• 1 30 x 20 cm board (or other smooth surface)

Instructions

• Begin the lesson by discussing the meaning of ‘viscosity’ with the children and explain that it is the scientific term used to describe the ‘runniness’ of a liquid. Encourage discussion about how runny a medicine would need to be, based on the children’s own experience. 
• Show children the three ingredients that could be used to produce a syrup to carry the active ingredient in the medicine they are producing: liquid glucose, glycerine and water.
• Next, ask the children to explain why, in a commercial environment, it is vital that a recipe is systematically recorded and reproduced so that it is identical each time? Is it important to accurately measure and record the amounts of the liquids used?  How can we ensure that the runniness is the same.
• Ask the children how they are going to measure the viscosity of the cough syrup samples they make. Show the children the equipment listed above and get them to work in groups to think which items could be used to test viscosity (e.g. timing a marble sinking through liquid).
• Once they have decided on a way to test viscosity the children can now begin their investigation. Encourage them to use different proportions, combinations and ratios of liquids (a total of 50 ml of any of the liquids combined is enough to obtain results).  Once a sample has been tested and recorded it can be changed to dilute or thicken and then retested provided the changes are recorded.
• Ask the children to explain results, which combination do you think would make the best cough mixture?   Explain your conclusion. 
• Ask the children to think about whether their tests were fair, their results reliable and whether there are any improvements that they could make to their tests.

Tip

• Link this activity to the subject of ratio in maths.
• Discuss the use of glucose in the recipe and the fact that sugar in medicines and food stuffs is bad for our health.

Health and Safety

• Remind the children not to drink their samples.

Links tothe National Curriculum for Science:

Working Scientifically

Learning Objectives

• planning different types of scientific enquiries to answer questions, including recognising and controlling variables where necessary
• Making measurements, using a range of scientific equipment, with increasing accuracy and precision, taking repeat readings when appropriate
• Use observations, measurements or other data to draw conclusions

Subject Knowledge

Learning Objectives

• Know that changes occur when materials are mixed