Learn methods to separate substances that are uniformly mixed or dissolved, specifically evaporation for solutions and churning for liquid emulsions.
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Hook connecting history to the evaporation of salt.
"How do we get the common salt (namak) we eat every day? Filtration won't work because salt is fully dissolved in seawater—it passes right through the filter paper! To extract it, we must use the process of Evaporation."
— A lesson inspired by the historic Dandi March at Sabarmati Ashram
Explain the process of evaporation to retrieve dissolved solids.
Evaporation is the process in which a liquid gets converted into its vapour. When used as a separation method, it is highly effective for separating a solid component that is completely dissolved in a liquid.
Visual showing large scale evaporation of seawater.
By keeping seawater in shallow pits, sunlight evaporates the liquid water over a few days, leaving the dissolved solid salts behind.
MCQ applying evaporation to a real-world scenario.
Why do white patches sometimes form on dark-coloured clothes worn during hot summer days?
Explain how churning separates lighter butter from curd.
Drinking cold chhach (buttermilk) on a hot day is extremely refreshing. But how is it separated from the original curd? This is done through a process called churning, which involves vigorously agitating or spinning a liquid mixture.
Fill in the blanks about the churning process.
In many homes, a traditional method is used to prepare refreshing dairy drinks during the summer. A common kitchen practice involves the process of curd using a tool like a mathni. This vigorous spinning helps to agitate and separate the mixture into two distinct components. In this process, the butter being separates and floats at the top. Meanwhile, the remaining liquid known as is left behind at the bottom. This mechanical separation method is an excellent example of obtaining two useful substances from a single mixture.