Perform this activity and answer the questions. Add salt half a teaspoon at a time to a clear glass of water, stirring well each time.
If more salt does not dissolve in the water, where does it go? Does it sink to the bottom of the glass or rise to the top? Why?
Important Questions on Separation of Substances
Perform this activity and answer the questions. Add salt half a teaspoon at a time to a clear glass of water, stirring well each time.
If you now heat the glass of salt water, can you dissolve more salt in it? What does this tell you?
Mention if the following separations are possible or not. Give reasons for your answers.
A mixture of salt and chalk powder can be separated by sieving.
Mention if the following separations are possible or not. Give reasons for your answers.
A mixture of oil and water can be separated by evaporating the water.
Mention if the following separations are possible or not. Give reasons for your answers.
Air that is dissolved in water can be removed by boiling the water.
You are given some mixtures of substances to separate. They fall under four categories: solid and solid (A), solid and liquid (B), liquid and liquid (C) and liquid and gas (D). Complete the table by filling in the details.
| Mixture | Category | Method of separation |
| (i) Rice and stones | ||
| (ii) Oil and water | ||
| (iii) Sand and water | ||
| (iv) Salt and sand | ||
| (v) Water and salt | ||
| (vi) Water and air | ||
| (vii) Vinegar and water |
Fill in the missing words and give the following verse a tune!
I've been churning and churning
My poor hands are _____ (rhymes with churning)
And now I am in doubt
I am tired and sore
I can't churn any _____ (rhymes with sore)
Why doesn't the butter come _____ ? (rhymes with doubt)
Churning by hand is a tiring job. How else can you make butter at home? Ask an adult and write the answer.
I've been churning and churning
My poor hands are burning
And now I am in doubt
I am tired and sore
I can't churn any more
Why doesn't the butter come out?
How is butter made in factories?
A saturated solution of salt in water can be made less saturated by
