The science of separation – 2

Avneesh Shukla

In the first part of this series (Separation Techniques – Part I – November 2016), we discussed some techniques that happen on a routine basis. In this article we will explore and learn about other techniques of separation of various substances by using easily available and local resources.

Can you think of an idea or method to separate water and oil?
alternate-apparatus Before going to the school, I worked on designing an alternate model/apparatus for separating water and oil. This reminded me of my college days where we separated two liquids using a separating funnel. After a discussion with colleagues, I finally designed a model using a water bottle, a straw, some clay (for sealing hole) and a needle as shown in the picture.

When I arrived at the school the next day, the school teacher said, “I was also thinking about the separation of oil and water but I didn’t get anything.” What the teacher said motivated me since I realized that she was also trying to find out the process or method of separation. This showed that she was eager and curious to learn. Without losing time I showed her my apparatus and then both of us entered the classroom. The students were then asked, “Can we separate oil and water?” They responded that it is impossible to separate the two. Then I asked them to list out other substances that cannot be separated. They responded, “Kerosene oil and water, mustard oil and water, refined oil and water, petrol and water, honey and water.”

In an earlier lesson on separation techniques, the students had reflected on how it was not possible to separate chalk powder and soil. Taking that further, I asked the students if they could separate
• Soil and salt
• Sand and salt
• Salt from salty water (mixture of salt in water)
• Sugar from sugar water (sugar solution in water)
• Salt and Naphthalene ball

Almost in unison they said, “We can’t separate them.” At this point, the class teacher referred to the process of salt formation from sea water by asking, “How is salt separated from salty water of sea?” When I did not receive any concrete answer, I concluded this discussion by giving a clue:
• If we continuously boil the salty water or sugar solution, what will happen?

The author is with the Azim Premji Foundation. He can be reached at

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