The DAV Class 6 Science Solutions and DAV Class 6 Science Chapter 4 Question Answer – Separation of Substances are essential study tools for DAV public school students in Class 6.
DAV Class 6 Science Ch 4 Question Answer – Separation of Substances
DAV Class 6 Science Ch 4 Solutions – Separation of Substances
Something To Know
A. Fill in the blanks.
Question 1.
Housewives sometimes use the method of ______ to remove unwanted substances from eatables like rice and pulses.
Answer:
hand picking
Question 2.
Common salt is prepared on a large scale through the process of ______
Answer:
crystallization
Question 3.
Separation of tea leaves from tea is done by a process called ______
Answer:
filtration
4. The process of ______ can be used to increase the rate of sedimentation of the suspended particles in a solid-liquid mixture.
Answer:
loading
Question 5.
The method, used to separate the fine particles, suspended in a liquid, by rotating the mixture at high speed, is known as ______
Answer:
centrifugation
B. Match the following:
| 1. Wind | (a) hand picking |
| 2. Chalk powder and water | (b) winnowing |
| 3. Oil and water | (c) sedimentation |
| 4. Separating peas from cooked pulao | (d) filtration |
| 5. Muslin cloth | (e) separating funnel |
| 6. Camphor and salt | (f) sublimation |
Answer:
| 1. Wind | b | (a) hand picking |
| 2. Chalk powder and water | c | (b) winnowing |
| 3. Oil and water | e | (c) sedimentation |
| 4. Separating peas from cooked pulao | a | (d) filtration |
| 5. Muslin cloth | d | (e) separating funnel |
| 6. Camphor and salt | f | (f) sublimation |
C. Tick (✓) the correct option.
1. Which of the following is an example of a heterogeneous mixture?
(a) Sugar in water
(b) Pebbles in rice
(c) An aerated drink
(d) Salt in water
Answer:
(b) Pebbles in rice
2. Which one of the following is not an example of a pure substance?
(a) Oxygen
(b) Air
(c) Copper
(d) Carbon dioxide
Answer:
(b) Air
3. The process of loading helps to
(a) Slow down the rate of sedimentation
(b) Speed up the rate of sedimentation
(c) Speed up the rate of decantation
(d) Slow down the rate of decantation
Answer:
(b) Speed up the rate of sedimentation
4. Transferring the clear liquid, into another container, leaving behind the residue, is called
(a) Sedimentation
(b) Decantation
(c) Condensation
(d) Crsytallisation
Answer:
(b) Decantation
5. A substance, that sublimes easily, is
(a) Naphthalene
(b) Salt
(c) Sugar
(d) Chalk
Answer:
(a) Naphthalene
D. Answer the following questions in brief.
Question 1.
Name any three methods used for separating solid-solid mixture.
Answer:
Three methods of separating solid-solid mixture are as follows:
(a) Hand-picking
(b) Threshing
(c) Winnowing
Question 2.
What is winnowing? Give an example of a mixture whose components can be separated by this method.
Answer:
Winnowing is used for separating lighter objects from heavier objects with the help of wind. This is used by farmers to separate grains from chaff. For this, the mixture is allowed to be dropped from a height. Husk being lighter gets blown away, while the grains fall vertically down.
Question 3.
Some iron pins get scattered on the carpet when you are expecting guests. How can you collect all the pins in the shortest possible time?
Answer:
Magnetic separation is ideal in this condition. I shall hover a magnet over the carpet. This will allow the iron pins to stick to the magnet.
Question 4.
Name any three substances which sublime on heating.
Answer:
Examples of sublimates: Camphor, naphthalene and ammonium chloride.
Question 5.
What is crystallisation? Name any three substances which can be purified using this technique.
Answer:
Crystallisation is used for obtaining pure solid from a solution. During crystallisation, pure sohd is obtained from a concentrated solution of the given substance. Three substances which can be purified using this technique are: salt, copper sulphate and alum.
E. Answer the following questions.
Question 1.
Differentiate between a pure substance and a mixture. Give two examples of each.
Answer:
| Pure substance | Mixture |
| Composed of the same material. | Composed of different materials. |
| Physical and chemical properties of all the components are same. | Physical and chemical properties of different components are different. |
| Examples: Salt, sugar. | Examples: Sugar solution, wheat and husk. |
Question 2.
State the difference between heterogeneous and homogeneous mixtures. Give two examples of each type.
Answer:
| Heterogeneous Mixture | Heterogeneous Mixture |
| Components are not uniformly distributed. | Components are not uniformly distributed. |
| Particles can be seen with naked eyes. | Particles can be seen with naked eyes. |
| Examples: Salt & sand, iron nail and pebbles. | Examples: Salt & sand, iron nail and pebbles. |
Question 3.
Can a mixture of iodine and camphor be separated by the sublimation method? Give reason for your answer.
Answer:
Both iodine and camphor are substances which undergo sublimation. Hence, a mixture of iodine and camphor cannot be separated by sublimation method.
Question 4.
Why does the size of naphthalene balls, put in open, keep on reducing with time?
Answer:
Naphthalene is a material which undergoes sublimation at room temperature. When naphthalene balls are kept in open, sublimation keeps going on in them. Due to this, the size of naphthalene balls reduces if they are kept in open.
Question 5.
After a dust storm, how does rain help in making the air clear?
Answer:
After a dust storm, rain water mixes dust particles and other substances in it as it comes down to the earth. Thus, rainwater helps in making the sky clear.
Question 6.
Sawdust, mixed in water, cannot be separated by the sedimentation method. Why?
Answer:
Sedimentation is a process during which heavier impurities settle down at the bottom. Sawdust is lighter than water and hence it cannot settle down at the bottom. Due to this, sawdust mixed in water cannot be separated by sedimentation method.
Question 7.
The filtration method cannot be used to separate sugar and salt mixed in water. Why?
Answer:
Filtration method is useful only in case of insoluble substance in water. Both salt and sugar are soluble in water. Hence, filtration method cannot be used to separate them from water.
Question 8.
Describe the method of centrifugation using an appropriate example.
Answer:
When insoluble particles are suspended in a liquid, they can be separated by this method. For this, the mixture is churned. The lighter particles separate because of centrifugal force. Cream is separated from milk by using this method.
Value Based Questions
The students, of Class VI, participated actively in the ‘Sivachata Abhiyan’ for their school and its neighbourhood. They separated out the biodegradable and non-biodegradable wastes and put them in separate bins. Their science teacher appreciated their work. She compared their work with the methods of ‘Sieving’ and ‘Winnowing’ about which she had taught them last week.
Question 1.
State the values displayed by the students of Class-VI.
Answer:
Care for environment, sincerity
Question 2.
Give one example each of a situation in which ‘sieving’ and ‘winnowing’ can be used for bringing about the required separation.
Answer:
Sieving can be used for separating bran from flour, while winnowing can be used for separating chaff from grains.
Question 3.
Have a discussion in the class, in which each group of students gives one example of ‘separation’ that can be compared with ‘some method of separation’, studied by them.
Answer:
Do it yourself.
Something To Do
Question 1.
Draw a neat and well-labelled diagram of filtration method. Also name the different varieties of filters available.
Answer:
Different varieties of filters:
- Filter paper,
- Muslin cloth.
- Charcoal.
- Fine sand,
- Cotton wool.
Question 2.
Fill a glass with impure water. Using your knowledge of methods of separation, suggest a method to purify it. Justify your suggestions.
Answer:
Impure water can be purified by using a combination of sedimentation, decantation and filtration, if it is assumed that the water does not contain soluble impurities. First of all, the container is left undisturbed for some time so that some solid particles would settle down at the bottom. Then the liquid is poured in another container by the method of decantation. The liquid thus obtained is poured in a funnel which is lined with a filter paper. The filtrate thus obtained would be pure water.
Question 3.
Suggest ways to separate the components of the following mixtures:
(a) Camphor, sand and salt
Answer:
First of all, camphor should be separated from this mixture by using sublimation method. Then, the remaining mixture of sand and salt should be mixed with water. Salt shall dissolve in water and then sand can be separated by using filtration. Finally, salt can be separated from water by using evaporation method.
(b) Sawdust, common salt and iron nails
Answer:
First of all. iron nails should be separated by magnetic separation. After that, sawdust can be separated by using a sieve which is made of a very fine mesh.
(c) Ammonium chloride, common salt and chalk powder
Answer:
First of all, ammonium chloride should be separated from the mixture by using sublimation. Then, the remaining mixture of the chalk powder and salt should be mixed with water. Salt shall dissolve in water and then chalk powder can be separated by using filtration. Finally, salt can be separated from water by using evaporation method.
Question 4.
Visit the kitchen in your house and also your surroundings. Observe the different methods of separation that are being used by different people. Make a list of your observations and name the different methods used in different cases.
Answer:
| Substances | Method of separation |
| Pebbles from rice | Hand picking |
| Bran from flour | Sieving |
| Tea leaves from tea | Filtration |
| Cream from milk | Centrifugation |
DAV Class 6 Science Chapter 4 Solutions – Separation of Substances
I. Fill in the blanks.
Question 1.
A ______ is composed of more than one materials.
Answer:
Mixture
Question 2.
A ______ is composed of only one material.
Answer:
Pure substance
Question 3.
Pebbles can be separated from rice by using ______ method.
Answer:
hand-picking
Question 4.
Magnetic separation is used for separating ______ articles from garbage heap.
Answer:
Iron
Question 5.
______ hastens the process of sedimentation.
Answer:
Loading
Question 6.
______ is often used as a loading agent during purification of water.
Answer:
Alum
Question 7.
Camphor can ______ at room temperature.
Answer:
Sublimate
Question 8.
Water can ______ at room temperature.
Answer:
Evaporate
Question 9.
A filter paper is normally used in ______
Answer:
Laboratory
Question 10.
Separation of tea leaves from liquor is an example of ______ method.
Answer:
Filtration
II. Tick (✓) the correct option.
1. Which of the following is a pure substance?
(a) Milk
(b) Salt
(c) Normal water
(d) Butter
Answer:
(b) Salt
2. Which of the following can undergo sublimation?
(a) Salt
(b) Sugar
(c) Petrol
(d) Camphor
Answer:
(d) Camphor
3. Which of the following is obtained after evaporation and crystallisation?
(a) Salt
(b) Copper sulphate
(c) Alum
(d) All of these
Answer:
(d) All of these
4. Components of which of these mixtures can be separated by using sublimation?
(a) Camphor and salt
(b) Camphor and iodine
(c) Camphor and naphthalene
(d) Camphor and ammonium chloride
Answer:
(a) Camphor and salt
5. Components of which of these mixtures can be separated by using hand-picking?
(a) Flour and salt
(b) Sand and salt
(c) Rice and pebbles
(d) Sugar and salt
Answer:
(c) Rice and pebbles
6. Components of which of these can be separated by using sieving?
(a) Cheese from whey
(b) Bran from flour
(c) Salt from water
(d) Sugar from water
Answer:
(b) Bran from flour
7. Petroleum products are obtained by using which of these methods of separation?
(a) Separating funnel
(b) Filtration
(c) Distillation
(d) Fractional distillation
Answer:
(d) Fractional distillation
8. Which method is suitable for separating mud from water?
(a) Sedimentation
(b) Decantation
(c) Filtration
(d) A combination of all the three
Answer:
(d) A combination of all the three
III. Answer these questions.
Question 1.
What do you understand by a pure substance?
Answer:
A substance which is composed of only one type of material is called a pure substance. All the components of a pure substance have similar chemical and physical properties.
Question 2.
What is a mixture?
Answer:
A substance which is composed of more than one type of substance is called a mixture. Different components of a mixture have different chemical and physical properties.
Question 3.
What is a homogeneous mixture?
Answer:
When the mixture has same composition throughout, it is called homogeneous mixture. The components of a homogeneous mixture cannot be distinguished. Examples: solution of salt and sugar in water, alloys, etc.
Question 4.
What is a heterogeneous mixture?
Answer:
When the mixture does not have same composition throughout, it is called heterogeneous mixture. The components of a heterogeneous mixture can be distinguished from one another. Examples: mixture of sand in water, iron nails in sulphur powder, pebbles in rice, etc.
Question 5.
What is sieving? Explain with suitable examples.
Answer:
Sieving is used to separate components of different sizes. A sieve is made up of a wire mesh which is tightly fixed in a frame. The mixture is put in the sieve and the sieve is shaken. The smaller particles pass through the mesh and larger particles remain in the sieve. This method is often used in households to separate impurities from flour. Sieving is also used at construction sites to separate pebbles from sand.
Question 6.
What is sublimation?
Answer:
A solid usually changes into liquid before changing into gas. But some solids directly change into gas and its vice-versa is also true. This phenomenon is called sublimation.
Question 7.
What is evaporation? How is it used as a method of separation of substances?
Answer:
The process by which a liquid changes into gas is called evaporation. By using this method, the liquid component is allowed to evaporate, which leaves the solid component. For example, from a solution of salt in water, salt can be obtained by using this method. In fact, salt is obtained from sea water by using this method.
Question 8.
What do you understand by sedimentation and decantation?
Answer:
The process by which heavy solid particles settle down on their own in a solution is called sedimentation. After sedimentation, the liquid component is carefully poured out without disturbing the sediment. This process is called decantation. Example: sand can be separated from water by using this method.
IV. Projects
Question 1.
Make a water filter by using some common materials available in your house. Make a note of the separation methods being used in this filter.
Answer:
A discarded plastic bottle can be used for this purpose. Some charcoal, pebbles, sand and muslin cloth can also be used. You can take help from an adult in this task.
Question 2.
Make a list of various methods of separation being used by your mother in the kitchen. Make a list of items which are being separated by these methods.
Answer:
Do it yourself.
Question 3.
Imagine that you are making paneer from milk. How many methods of separation are being used during this?
Answer:
Do it yourself.