Separation of Substances

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Questions and Answers

Why do we need to separate different components of a mixture?

To remove harmful or non-useful substances, and to use useful components separately.

What is winnowing?

Winnowing is a method used to separate heavier and lighter components of a mixture using wind.

How will you separate husk or dirt particles from a given sample of pulses before cooking?

By washing the pulses in water and allowing the impurities to settle or by handpicking.

What is sieving, and where is it used?

Sieving is the process used to separate finer particles from coarser ones using a sieve. Signup and view all the answers

How will you separate sand and water from their mixture?

By letting the sand settle at the bottom and then using decantation or filtration. Signup and view all the answers

Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?

Yes, by using a process that allows for sieving, as sugar is finer than flour. Signup and view all the answers

The method of separating seeds of paddy from its stalks is called __________.

threshing Signup and view all the answers

How would you obtain clear water from a sample of muddy water?

By using sedimentation and decantation, or filtration to remove impurities. Signup and view all the answers

When milk, cooled after boiling, is poured onto a piece of cloth, the cream (malai) is left behind on it. This process of separating cream from milk is an example of __________.

filtration Signup and view all the answers

Salt is obtained from seawater by the process of __________.

evaporation Signup and view all the answers

Impurities settled at the bottom when muddy water was kept overnight in a bucket. The clear water was then poured off from the top. The process of separation used in this example is called __________.

decantation Signup and view all the answers

A mixture of powdered salt and sugar can be separated by the process of winnowing.

False Signup and view all the answers

A mixture of milk and water can be separated by filtration.

True Signup and view all the answers

Separation of sugar from tea can be done with filtration.

False Signup and view all the answers

Grain and husk can be separated with the process of decantation.

False Signup and view all the answers

Should you add ice to the lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar?

You should add ice after dissolving sugar to allow more sugar to dissolve. Signup and view all the answers

Study Notes

Separation of Substances

In our daily life, we often need to separate substances from a mixture of materials.
- Examples: separating tea leaves from liquid, butter from milk or curd, grain from stalks, and salt from a mixture.

Handpicking

Handpicking is a convenient method of separating slightly larger impurities from a substance.
- Example: separating stones, husks, and broken grains from wheat, rice, or pulses.

Threshing

Threshing is a process used to separate grain seeds from stalks.
- Example: farmers use threshing to separate grain from stalks, and machines are also used to thresh large quantities of grain.

Winnowing

Winnowing is a method of separating heavier and lighter components of a mixture by wind or by blowing air.
- Example: farmers use winnowing to separate lighter husk particles from heavier seeds of grain.

Sieving

Sieving is used to separate components of a mixture based on their sizes.
- Examples: separating pebbles and stones from sand, and removing impurities from flour.
- Sieving is commonly used in flour mills to remove impurities like husk and stones from wheat.

Sedimentation, Decantation, and Filtration

Sedimentation is the process of separating heavier components from a mixture that settle at the bottom of a container.
Decantation is the process of pouring out the top layer of a mixture, leaving the heavier components behind.
Filtration is the process of separating components of a mixture based on their ability to pass through a filter.
- Examples: separating rice or pulses from impurities like dust or soil particles, and separating water from insoluble impurities like soil.

Evaporation

Evaporation is the process of converting water into its vapour.
Evaporation can be used to separate a mixture of water and salt.
- Example: sea water is evaporated to obtain salt, and common salt is then obtained from this mixture of salts by further purification.

Condensation

Condensation is the process of converting water vapour into its liquid form.
- Example: steam from a kettle condenses into liquid water when it comes into contact with a cooled surface.

Uses of More than One Method

Often, one method of separation is not sufficient to separate the different substances present in a mixture.
In such cases, more than one method is used to separate the substances.
- Example: separating salt, sand, and water using processes of decantation, filtration, evaporation, and condensation.### Separation of Substances
Substances can dissolve in water and form a solution, and many substances are soluble in water.
If we go on adding more and more of a substance to a fixed quantity of water, a point will be reached where the solution becomes saturated, meaning no more of that substance can be dissolved in the water.
Water cannot dissolve an unlimited amount of a substance, and the amount it can dissolve varies from substance to substance.

Dissolving Salt in Water

When dissolving salt in water, if we go on adding salt, one teaspoonful at a time, and stir, eventually the solution will become saturated, and no more salt can be dissolved in the water.
If we heat a saturated solution of salt in water, more salt can be dissolved in it.
Once the hot solution cools, the salt appears to settle at the bottom of the beaker again.

Solubility of Different Substances

Water dissolves different amounts of different soluble substances, as shown in Table 3.2.
For example, salt and sugar are both soluble in water, but they dissolve in different amounts.

Methods of Separating Substances

Handpicking: separating husk and stones from grains.
Winnowing: separating husk from heavier seeds of grain.
Sieving: separating particles of different sizes in a mixture.
Decantation: separating sand and water from their mixture.
Filtration: separating components of a mixture of an insoluble solid and a liquid.
Evaporation: separating a solid dissolved in a liquid.

Applications of Separation Methods

Sieving is used in separating components of a mixture of different sizes.
Filtration is used in separating components of a mixture of an insoluble solid and a liquid.
Evaporation is used in separating a solid dissolved in a liquid.

Separation of Substances from Mixtures

Husk and stones can be separated from grains by handpicking.
Husk is separated from heavier seeds of grain by winnowing.
Difference in the size of particles in a mixture is utilised to separate them by sieving and filtration.
In a mixture of sand and water, the heavier sand particles settle down at the bottom and the water can be separated by decantation.