STD 6 Basic Science: Chapter 09 Mix and Separate - Questions and Answers | Teaching Manual


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Chapter 09: Mix and Separates - Questions and Answers 
1. You are all fond of sugar candies. Have you tasted sugar candies? What is its taste? What other specialities does the sugar candy possess?
Examine and write.
Answer:
• Colour - White
• Odour - No Odour
• State - Solid state

2. Break a small crystal of the sugar candy and observe it using a hand lens. Is it possible to break it further?
Answer: Yes

3. What is a Molecule?
Answer: The smallest particle of a substance retaining all the properties of that substance is known as its molecule. 
Substances that exist in the solid, liquid and gaseous states are made up of molecules.

Pure Substances
4. What is a pure substance? Give Examples.
Answer: If a substance contains only one type of molecule, it is known as a pure substance.
Examples: Water, Salt, Baking soda, Oxygen, Aluminium, Copper, Silver, Glycerine, Potassium permanganate, Copper sulphate (Blue vitriol)

5. What molecules will be present in a solution made by dissolving sugar candy in water?
Answer:
• Molecule of sugar candy
• Molecule of water

6. What is a pure Mixture? Give some examples.
Answer: If there is more than one type of molecule present in a substance, it is called a mixture.
Example: Sugar solution, Air etc.

7. Examine the table given below.
 Substance Molecules present
  Sugar solution Sugar, water
  Soda Water, Carbon dioxide
  Oxygen Oxygen
  Air Nitrogen, Oxygen, Water vapour, Carbon dioxide
  Mercury Mercury
  Iron Iron
  Copper sulphate (Blue vitriol)  Copper sulphate
Analyse the table and classify them into pure substances and mixtures.
Answer:
Pure Substance
• Oxygen
• Mercury
• Iron
• Copper sulphate
Mixture
• Sugar Solution
• Soda
• Air

Different types of mixtures
8. Fill two glass tumblers with water. Put some salt in one tumbler and chalk powder in the other and stir well. After some time, examine both these glasses with a lens. What differences do you observe?
Answer: In the solution of chalk powder with water chalk powder will settle down at the bottom of the glass tumbler but in the salt solution, salt will completely dissolve in the solution.

9. Do salt and chalk powder get distributed in water in the same way? 
Answer: No salt will be distributed in all parts of the water, but chalk powder will distribute only to the bottom of the water containing glass Tumblr.

10. Using a straw, taste the salt solution from different parts of the solution.
Answer: Yes

11. What are the different types of mixtures?
Answer: 
• Homogeneous Mixture
• Heterogeneous Mixture

12. What is a Homogeneous Mixture?
Answer: If a mixture exhibits the same property throughout, that mixture is called a homogeneous mixture.
Example: Saltwater

13. What is Heterogeneous Mixture?
Answer: If a mixture exhibits different properties in different parts, that mixture is called heterogeneous mixture.
Example: Chalk powder dissolved in water 

14. Haven't you observed the solution of chalk powder in water? Are the chalk particles distributed uniformly in the mixture?
Answer: No

15. Take some buttermilk in a glass tumbler and observe. What all particles do you see? Are they distributed uniformly?
Answer: Water, curd, curry leaf, ginger, and chilly are observed but these are not uniformly distributed in buttermilk.

16. Classify them into homogeneous and heterogeneous mixtures.
 homogeneous mixture heterogeneous mixture
  Dilute Acid Curry
  Alcohols Sand in water
  Tea, Coffe Soil
  Salt solution Rice soup
  Atmospheric Air Sand
  Metal alloys 

Different types of solutions
17. Examine the table
 Solution Constituent  particles
  Brass Zinc, Copper
  Soda Water, Carbon dioxide
  Glycerine dissolved in water Glycerine, water
  Air Nitrogen, Oxygen, Water vapour, Carbon dioxide
Based on the constituent particles, identify the characteristics of each solution.
Answer:
• Brass  - Solid dissolved in solid
• Soda - Gas dissolved in solid
• Glycerine dissolved in water - Liquid dissolved in liquid
• Air - Gas dissolved in Gas

Separation of mixtures
18. Add some sand in a glass of water and stir well. What will be the result?
Answer: Sand particles settle down at the bottom of the glass.

19. Add some salt to water taken in another glass. What happens to the salt?
Answer: Salt dissolves in water. 

20. What difference do you notice in the mixtures in the two glasses?
Answer: Mixture of sand and water does not show the same quality. Thus the mixture is heterogeneous. But salt dissolves completely in water and the properties are same in all parts. So salt solution is a homogeneous mixture

21. How can you separate sand from a mixture of sand and water?
Answer: Take the mixture of sand and water in a beaker and stir well, then keep it still for some time. After some time sand will settled down at the bottom of the beaker. The clear water on the top portion can be poured out. Thus we can separate sand and water from the mixture.

22. Which property of sand helped you in separating it in this method?
Answer: Sand is a high-density solid particle and it could not dissolve in water. This property of sand helped in this method.

23. Can you separate salt from salt water?
Answer: Yes. We can separate salt from water when. Salt solution is heated and evaporated, the water will get vaporized and salt will remain. This process is known as evaporation. Salt cannot be separated using sieve or filter paper.

24. What is Decantation?
Answer: Decantation is the process of separating the clear liquid above after sedimentation of the components of a mixture.

25. Is the water obtained after decantation clear?
Answer: No.

26. What property of the substance is made use of when the constituents of a mixture are separated using a sieve?
Answer:
• Difference in the size of the particles. 
• Components are immiscible.
• Difference in the density.
• One of the components must be insoluble.

27. How can you separate the constituents of a mixture of chalk powder and water? What all materials are required? Do the experiment and record it in your science diary.
Experiment
Required materials: Filter paper, funnel, beaker, glass rod, conical flask. Method of experiment
A folded filter paper kept in a funnel, and this funnel placed in a conical flask as shown in the picture. Then take the mixture of chalk powder and water in a beaker and pour it into the funnel using a glass rod.
Observation
The chalk powder in it gets collected in the filter paper and clear water gets collected in the conical flask.
Reason
Filter paper is a special type of paper used for separating particles which are not dissolved in a solution. Filter paper is thicker and has very minute pores. So water can pass through the tiny holes of a filter paper but chalk particles, being large, cannot pass through the tiny holes of the filter paper, which remains on the filter paper. This process is known as filtration.

28. Can you separate salt from salt solution using a sieve? Try to separate it using filter paper.
Answer: We cannot separate salt from salt solution using save or filter paper. Because salt will dissolve in water.

29. Heat salt water in a steel spoon using a spirit lamp. What is left behind in the spoon when the water gets evaporated? Taste it. 
Answer: When we heat salt water in a steel spoon using spirit lamp, we can obtain salt from salt water by evaporation. But water cannot be collected during evaporation, it is lost into the air.

30. What is Filtration?
Answer: Filtration is the process of separating the constituent particles of a mixture using a sieve.

31. What is Evaporation?
Answer: Evaporation is the process by which a liquid absorbs heat and gets converted to vapour.

32. Which other mixtures can be separated into constituents through evaporation?
Answer:
• For the separation of sodium chloride (common salt) from seawater.
• For the separation of sugar from its solution
• For the separation of sand from muddy water

33. Which is the source of heat required to evaporate water in salt pans?
Answer: Sun is the source of heat required to evaporate water in salt pans.

Separating Iron powder
34. Remains of iron powder and aluminium powder while cutting iron and
aluminium pipes stay mixed in a workshop that fabricates metal doors and
gates. How can you separate iron powder from aluminium powder in this
mixture? Are any of the methods we have come across suitable for this? Select the suitable material from those given below and try to separate.
Spoon, Filter paper, Funnel, Tea strainer, Magnet, Test tube
Answer: Magnet

35. What property of iron powder did you make use of in this case?
Answer: Magnetic property of Iron.

36. What other instances do you know where the constituents of a mixture need to be separated? Observe the pictures. (TextBook Page: 121)
Answer:
• Removing the sediment from the juice of sugar cane.
• Removing the sediment from tea.
• Removing stones and paddy from rice.
• Removing chaff from paddy.
• Removing remains of lemon from its juice. 
• Separation of impurities from jaggery. 
• Separation of water from Curd.
• Separation of sand from gravel. 
• Removing impurities from mustard. 
• Removing mud from water.
• Separation of salt from seawater.

37. Are you familiar with the extraction of coconut oil from copra? What method is used in our homes to separate copra cake from coconut oil? Find out.
Answer: We can separate coconut oil from copra cake using clean cotton cloth peace.

Sand as a good sieve
38. Observe the picture (Textbook Page: 121). Does the water from the septic tank get mixed with sand? Why is the water in wells clear?
Answer:  Water flows through the soil. Soil will contain large number of small pores. This water will penetrate through these pores, then it will filtrate well.

39. Is there any chance for the water in the well to get contaminated if the septic tank is close to the well?
Answer: Yes, well is near the septic tank, water from the septic tank will easily penetrate through the pores of the soil and it will arrive at the well. Here complete filtration by the soil is not possible.

40. Record in your science diary the precautions to be taken while constructing septic tanks.
Answer: 
• Septic tank must be 15 metres away from the water source.
• Septic tank will contain minimum 4 compartments. Construction of tanks in hard soil is necessary.
• Top of the tank will concrete well, and make sure it does not any leakage.
• Make sure the quality of pipes are good.

41. We are now familiar with different methods that are employed to separate the constituents of a mixture.
Complete the concept map by writing the methods employed and cite
examples.
Let us Assess
1. Observe the materials given below.
(i) How can you separate the components if A and B get mixed?
Answer: By using a magnet

(ii) How can you separate the components if A and C get mixed?
Answer: Mix water, then filter and remove the wax powder. To get salt to evaporate.

(iii) How can you separate the components if A and D get mixed?
Answer: Mix with water. Wax flotes and sand settle down. To separate wax filter it.

2. Using which equipment will you get water with maximum purity while
filtering muddy water? Why?
a. Cloth    b. Filter paper     c. Tea strainer
Answer: Filter paper
In filter paper, the pores are very small. So even tiny particles can be filtered. 

3. How does pure water differ from sugar solution based on the constituents present in them?
Answer:
• Pure water is a pure substance. It contains only molecules of water.
• Sugar solution is a mixture which contains molecules of water and sugar.

Extended Activities
1. Find out what all mixtures are prepared in the kitchen daily. Also
examine whether constituents are being separated from mixtures. Which
equipment are used for this purpose?
 Mixture   The component,
which is separated 		 Subject 
  Curd Butter Chum
  Tea Sediment of tea Sieve
  Lemon Juice  Remains of lemon juice Sieve 
  Rice chaff, stone Muram
(A Sieve to winnow grain)
  Sedimented water  dust Clean cloth
  Rice powder has large particles large size particles Sieve













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