Chapter 5 Separation of Substances

When two or more components mixes with each other, then it is known as mixture. When two or more components are there and we need one component from the mixture then we need to separate them. There are different techniques for separation like handpicking, winnowing, sieving and many more are there. For example:

1. If we want to separate grains or pulses from the stones, then handpicking method will be used.
2. If we want to separate husk or dust from the grains, then by winnowing method it is easy to separate.

Winnowing is a separation technique which is used to separate the lighter components from the heavier components. This method is generally used to separate grains from the husk or dust. By this method, lighter particles like dust are just blew out with air.

Here we use handpicking method to separate husk or dust particles from the given sample of pulses before cooking. Generally hand picking method is used to separate the large particles from the smaller ones. This method is used at home usually.

Sieving is a separation method or technique which is used to separate different size of particles. By sieving, fine particles are separated from the larger one. This method is generally used to separate fine particles of flour from the impurities and the larger particles. In this method, sieve has small holes through which fine particles of flour pass easily.

Sand and water from their mixture can be separated by filtration, decantation or by sedimentation method.

• By using filtration method, the large particles of sand can be separated from mixture but this method is not so useful.
• By using decantation method, we separate out the pure layer of water from the insoluble sand which settle down at the bottom.

By using the sedimentation method, the sand particles settle down at the bottom when the solution left undisturbed. Then we can separate the sand from the water easily.

Yes, it is possible to separate sugar mixed with flour of wheat. As we know sugar particles are larger in size as compared to wheat flour. Wheat flour have fine particles. So by using sieving method, we can do separation of sugar from the wheat flour. From the sieve the larger particles of sugar are separated while the fine particles of wheat flour pass through it easily.  

By using decantation or sedimentation method. We can separate clear water from a sample of muddy water. By decantation method, upper fine layer of pure water can be removed. By using sedimentation method, when we left the muddy water undisturbed for sometimes. Then the larger particles of mud settle down in the bottom and fine layer of pure water is obtained at the top of muddy water.

(a) Threshing

Threshing is the method of separation which is used to separate the grains from the stalk of the plant. In this method, stalks are beaten on the hard surface like drum or it can also be done by machines.

(b) Filtration

Filtration is the method of separation which is used to separate pure solution from the impure ones or from the larger particles.

(c) Evaporation

It is the process in which water evaporates from the sea water or we can say water converts into vapours.

(d) Decantation

Decantation is the method of separating two immiscible components from each other.

(a) False

No, both are miscible components and make a homogeneous mixture. So we cannot separate them by filtration.

(b) False

We cannot separate them by winnowing method because in powdered form they both will make a homogenous mixture.

(c) True

Yes, it is so because by filtration the larger particles of sugar can be separated whereas the solution of tea can pass through it easily.

(d) False

No, because decantation method is used for two immiscible components. This can be done by winnowing.

We should add ice to the lemonade after dissolving sugar because when we add ice before the sugar dissolution; the sugar will take time to dissolve in that cool solution. At the lower temperature, sugar dissolving capacity becomes weaker or lower.