Cleaning of food and separation of substances - Class 6 Science - New St. Mery English School 

This lesson covers why food needs to be cleaned before cooking and the different methods used to remove impurities. Students will also understand various separation techniques such as handpicking, winnowing, sieving, sedimentation, decantation, filtration, evaporation, and distillation. Perfect for CBSE Class 6 students, teachers, and parents looking for clear notes with simple examples.

Cleaning of food and separation of substances - Class 6 Science - New St. Mery English School

 1:- What is substance?

Ans:-  substance is a matter which has specfic composition or properties.

Ex- sugar, salt etc.

Every pure element is a substance. Every pure compound is a substance.

2:- How many types of substance? Name them.

Ans:- There are three types of substance

1-Pure substance

2- Impure substance

3- Mixture

3:- What is pure substance?

Ans:-A substance that contaons only one element or compound is called pure substance.

For example:- iron, water, sugar, salt etc.

4:- What is impure substance?

Ans:-  Impure substance is made up of two or more than two elements or compounds that are not bounded together chemically.

For example:- sugar in water, sand in water, fruit juice, muddy water etc.

5:- What is mixture?

Ans:-A mixture is the physical combination of two or more substances in which all substances are retained their identities. The components of mixture can be separated by physical mean.

Ex- salt water, mixture of water and sugar

Write three features of mixture.

Ans:- The three features of mixture are

1- The constituents  of a mixture are not present in a fixed ratio.

2- No chemical reaction takes place among the constituents of a mixture.

3- The constituents of a mixture retain their original properties.

6:- How many types of mixture? Name them.

Ans:- There. are three types of mixture.

1-Solid mixture

2-liquid mixture

3-gaseous mixture

7:-Write two example of solid mixture.

Ans:-soil, food grains

8:- Write six example of liquid mixture.

Ans:- tap water, syrup, a cup of tea, sea water, petroleum

9:- write an example of gaseous mixture.

Ans:- air

Why do we need to separate the substances from a mixture?

Ans:- we need to separate the substances from a mixture for the following reason.

1- To remove undesirable and harmful substances.

2- To obtain pure substances

3- To obtain desirable substances

10:- How many types of practices that can be help us in separating solid from other solid?

Ans:- There are five practices that can be help us in separating solid from other solid.

1-harvesting

2-threshing

3-winnowing

4-Hand picking

5-sieving

11:- what is harvesting?

Ans:- Harvesting is the process of gathering ripe crops from the field.There are two methods to harvest crops.

1-By hand using sickle

2-By harvester

12:- Write short notes on hand harvesting using sickle.

Ans:- Hand harvesting is done by small farmers. In hand harvesting crops are cut by hand using sickle at the root level. The harvested crop plants are made into stacks and are dried in sun. The dried stacks are then thrashed to separate grains from the stalks and the husk.

13:- What is Threshing?

Ans:- Threshing is the process of loosening the edible part of grain from the chaff to whichit is attached. 

 

14:- Write short notes on threshing.

Ans:- Threshing is a process in which crops are thrashed to get fine grains. Threshing is done by three process.

   1- By beating on hard surface

   2- Trampling by the cattle

   3- By thresher

15:- Write short notes on the trampling by the cattle.

Ans:- In trampling by cattle harvested spikes are sprad on the ground in a circle and bullocks tied to a central axis are made to walk over them in rounds. Cattle's tread upon the spikes and their hoofs help separate the grains, leaving behind a mixture of broken straw, chaff and the grains.

16:- What is winnowing?

 Ans:- Winnowing is farming method   developed by ancient people for     seperating grain from chaff.

17:- Write short notes on winnowing.

  Ans:- Winnowing is used to separate fine grains from straw and chaff with help of blowing wind. In this method farmers stand on a high platform facing the direction of wind and releasing the mixture of straw, chaff and grains form a winnow. Grains beings heavier fall under the winnow. Straw and chaff are being lighter and belown a little away by wind.

18:- What is hand picking?

Ans:- Hand picking is used to remove undesirable components like small pieces, and many other impurities from the grains.

19:- Write two places where hand picking is used.

Ans:- The two places where hand picking is used are 

      1- In separating impurities from grains.        2- In separating unripe fruits from ripe fruits.

20:- What is sieving?

Ans:- Sieving is a process in which fine particles are separated from bigger particles by using sieve.

21:- Write six places where sieving process is used to separate fine particles from large particles.

Ans:- The six places where sieving process is used are.

  1- Separate large sized grains from finer impurities.

  2- Separate bran from flour.

  3- Grade nuts of different sizes.

  4- Separate fine sand from coarse sand or pebbles.

  5- Large pearls from small pearls.

  6- Precious stones of different sizes.

22:- What is floating and sinking method?

Ans:- Floating and sinking method is used to separate the two components from a mixture in which both are solids but one floats and other sinks in water. 

         For example - To remove the dust and straw from the grains.

How many types of practices that can be help us in separating solid from liquid?

Ans:- There are two practices that can be help us in separating solid from liquid.

1-Sedimentation and decantation

2-Filtration

23:- What is Sediment?

Ans:- Insoluble solid particles which settle down in water is called sediment.

For example:- soil, chalk, sand etc.

24:- What is sedimentation?

Ans:- The process in which insoluble solid settling down in water is called sedimentation.

25:- What is decantation?

Ans:- pouring out liquid without disturbing the sediments is called decantation.

26:- What is solute?

Ans:- The substance that is soluble in any medium is called solute.

For example- sugar, salt, wax etc.

27:- What is solvent?

Ans:- The liquid in which a solute gets dissolved is called a solvent.

For example:- water, milk, kerosene etc.

28:- What is solution?

Ans:- The transparant mixture that is formed when solute dissolve in solvent is called solution

For example:- mixture of water and salt, mixture of water and sugar

29:- What are miscible liquids?

Ans:- Liquids which mix together in all proportions and form a single layer are called miscible liquids.

For example- milk and water , glycerine and water etc.

30:- What are immiscible liquids?

Ans:-  Liquids which do not mix with each other and form separate layers are called immiscible liquids.

For example- solution of oil and water

31:- What is loading?

Ans:- Loading is a process in which the rate of sedimentation is increased by adding chemical substances like alum.

32:- How does alum work as a loading in muddy water? Explain.

Ana:-  Alum is highly soluble in water. Particles of alum get attached to the clay of muddy water. This increases the weight of mud particles. These heavy particles of alum and dust together settle down fast. And make the water clean fastly.

33:- What is filtration?

Ans:- Filtration is a process that is used to separate an insoluble impurities from a liquid. Strainer, filter paper, wire-mesh and clothes are used as filter equipment for filtration.

34:- Write the name of some solid liquid mixture that is filtered by filtration process.

Ans:-Milk from milkman which include some straw

water from river or pond that have have solid impurities

Tea is filtered for separate tea leaves

35:- What is evaporation?

 Ans:- The process by which a liquid changes into gas is called evaporation.

36:- How can be increase the rate of evaporation?

 Ans:- We can increase the rate of evaporation by.

     1- Increase the temperature

     2- Increase the surface area of liquid

     3- By fast blowing air

37:- What is crystallization?

 Ans:- Formation of crystals of salt on evaporation of water from a solution of salt is called crystallization.

38:- What is condensation?

 Ans:- The process by which a gas or water vapour changes into liquid is called condensation.

39:- Write three magnetic metal names.

 Ans:- 1- Iron 

           2- Cobalt 

           3- Nickel

40:- What is magnetic separation?

 Ans:- Magnetic separation is the process of separating magnetic materials from magnetic and non magnetic mixture with the help of magnet.

   For example - we can separate mixture                of iron filings and sand by the.                       process of magnetic separation.

41:- What is churing?

  Ans:- Churning is the process that is used to separate cream from milk or curd.

42:- How many types of machines are used in churning?

 Ans:- 1- Wooden ladle

           2- Electrically operated blender 

           3- Churner

43:- How churning helps us in getting butter from curd?

Ans:- Firstly curd is churned with the help of churning machine. Churning machine separates the butter from curd. Butter is lighter than the milky water therefor it start to float above the milky water. By this process we can separate butter from curd.

What is Centrifugation?

Ans:- Centrifugation is a process of separating components of a mixture by spinning it rapidly, so that heavier particles settle down and lighter particles remain on top.

 

Centrifugation is a method used to separate a mixture of solid and liquid or two liquids that have different densities.

It is done using a machine called a centrifuge, which spins very fast.

Ex:- Separating cream from milk

        Separating mud particles from water in a lab

        Separating blood components (in hospitals)

How does a centrifuge work?

Ans:- When the mixture is spun very fast in a centrifuge , heavier particles move to the bottom and Lighter particles stay at the top.