Separation of Insoluble Solids from Water

Lesson Plan of Separation of Insoluble Solids from Water

General Science Grade IV

Students’ Learning Outcomes

·         Predict and demonstrate how various materials mix with water.
·         Demonstrate separation of insoluble solids from water by decantation and filtration.

Information for Teachers

·         The substances which dissolve in water are known as soluble substances and the resulting mixture is known as an aqueous solution.
·         The substances which don’t dissolve in water are termed as insoluble.
·         Insoluble solids can be separated from the mixture by the following two method:
v  Decantation is process in which upper liquid is poured off from the settled solid.
v  Filtration is a process in which insoluble substance is separated from the mixture with the help of a filter paper.

                                      Material / Resources

Water, sugar, glass, spoon, common salt, chalk powder, soil, glucose, lemon juice and vinegar, textbook




·         Ask the students: Tell anything that is soluble in water. Get the students response and do the following.
·         Take water in a glass. Add a spoon full of common sugar in it and stir.
·         Ask a student to bring some lemons then add lemon juice in a glass.
·         Inform students that this is how we make lemon squash.
·         Inform them this is how various materials mix with water.
·         Now mix some sand in water and stir it. Ask students to observe. Did the sand dissolve? (No) why not? ( because sand is insoluble)
·         Can we separate the sand from the water?  (multiple responses)
·         Ask them about sieving the tea leaves from the tea? Why do we do so? Do you know what this process is called? Tell them that this process is called filtration.
·         Explain how filtration helps us in daily life.




Activity 1

·         Take the following three solids. (Common salt, Sugar and Sand)
·         Ask three students to come forward. Give each of them a glass and ask them to half fill it with water.
·         Give one of the above solids to each student and ask them to add one spoonful of solid in water and stir it.
·         Show all the three glasses to the whole class and ask the following questions.
v  Which solid has disappeared in water?
(Students’ response: Common salt and sugar disappear in water or they are soluble in water)
v  Which solids didn’t disappear in water?
(Students’ response: Sand doesn’t disappear in water or it is insoluble in water)

Activity 2

·         Give a student mixture of water and sand.
·         Allow the sand to settle down.
·         Ask a student to carefully decant all the water into another glass.
·         Ask the students to name the process involved in this activity. (Decantation)
·         Inform them that decantation can be used to separate water from an insoluble substance with settles down.
·         Ask the students to give other examples of decantation (Multiple responses)

Activity 3

·         Take a glass and add water then ask student to add a spoonful of soil in the glass and stir it.
·         Let the above mixture stand for a few minutes.
·         Ask the students:
v  Have all the particles of soil settled down in water just like the particles of sand?
(No some are still suspended)
v  How can suspended particles of sand be separated?
(Students’ response: Multiple responses) Tell them that to separate the particles suspended in water we will use another method called filtration.

Demonstration for filtration

·         Take a filter paper. Fold it twice to have four folds.
·         Keep three folds on one side and one fold on the other side so that it gets the shape of a cone as shown in the figure.
·         Moisten the filter paper with a drop of water and fix it in the glass funnel as shown in the figure. (Size of the filter paper should be smaller than the size of the funnel)
·         Ask a student to drop the mixture of soil and water on the three fold side of the filter paper with the help of a glass rod.


·         Ask students to observe and report what happens.  


·         Inform the students that clean water will trickle down drop wise through the filter paper in the beaker lying underneath the funnel. It is called filtrate. The soil will remain on the filter paper. It is called the residue.


Sum up / Conclusion

·         Solids which dissolve in water are called soluble solids.
·         Solids which don’t dissolve in water are called insoluble solids.
·         If the particles of insoluble solids settle down in water, they can be separated by decantation.
·         The mixture in which the solid particles remain suspended can be separated by filtration.


·         Write the following list of substances on the board and ask the students to separate them as soluble or insoluble. Sand, washing soda, ultramarine, marble pieces and glucose. Suggest a material other than filter paper which may be used for filtration.
Washing soda (Na2 Co3)
Ultramarine (Neel)
Marble pieces

Follow up

·         Ask the students that how do you make the water obtained from a canal free from impurities?
(Students’ response: It is either filtered through a filter bed or through a cotton cloth).
·         Can the mixture of common salt and water be separated by the process of decantation or filtration?

·         Give examples of filtration from everyday life,

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