Question:
(a) When it is useful to apply sedimentation and decantation?
(b) Give an example where these methods are used?
(c) Explain the process.
Answer:
(a) Sedimentation and Decantation are used to separate coarse particles of a solid which is insoluble in the liquid. Sedimentation works on the property that heavy particles settle down due to gravity.
(b) e.g. sand in muddy water can be separated using sedimentation and decantation technique. Another example is to remove dust from rice. When water is added, rice grains being heavy settle down while the dust remains floating on the water.
(c) The particles of sand particles settle down to the bottom of the beaker. The settling down of heavier particles is called sedimentation. We can transfer the clear water in the upper layer (supernatent) carefully to another beaker without disturbing the solid partciles. This is called decantation.
Is Matter Around Us Pure?
Q 1.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 2.
What is a solution? What are the properties of a solution?
Q 3.
State the differences between compounds and mixtures.
Q 4.
What are the characteristics exhibited by a pure substance?
Q 5.
What are the properties of suspensions?
Q 6.
What are the differences and similarities between concentration and solubility?
Q 7.
Name two properties of a substance to check its purity?
Q 8.
What are the reasons for separating the constituents of a mixture?
Q 9.
What factors affect the solubility of solvent and solute?
Q 10.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 11.
What are suspensions? Explain with an example.
Q 12.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293K. Find its concentration at this temperature.
Q 13.
What is meant by a pure substance?
Q 14.
How crystallization is better than evaporation?
Q 15.
Why air is a mixture not a compound? Give reasons.
Q 16.
What are the advantages of preparing solutions?
Q 17.
Name the elements are in liquid state at room temperature.
Q 18.
Based on the type of solvent, how solutions are classified?
Q 20.
Based on the amount of solute in the given solution, how solutions are classified?
Q 21.
What are the properties of a colloid?
Q 22.
How many elements are there which are in gaseous state at room temperature?
Q 23.
List the points of differences between homogeneous and heterogeneous mixtures.
Q 24.
A good method to separate alum (phitkari) from impure samples is
(a) Filtration
(b) Sedimentaion
(c) Crystallization
(d) Sublimation
Q 25.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 26.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 27.
State three reasons why you think air is a mixture and water is a compound.
Q 28.
How will you separate iron pins from sand ?
Q 29.
What are the various methods to express concentration of a solution?
Q 30.
Name the technique to separate
(i) butter from curd
(ii) salt from sea-water
(iii) camphor from salt
Q 31.
Name the process you would use to separate a mixture of two miscible liquids (like acetone and water).
Q 32.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 33.
What is meant by Solubility?
Q 34.
What is Chromatography?
Q 35.
Fill in the following blanks with suitable words :
(a) An element is made up of only one kind of...........atoms
(b)Brine is a..........whereas alcohol is a.......
(c) Brass is an alloy which is considered a..........
(d) The three important metalloids are.............and...........
(e) The elements which are sonorous are called...............
Q 36.
What is difference between colloids and suspensions ?
Q 37.
21.5 g of sodium chloride dissolves in 60 g of water at 25°C. Calculate the solut water at that temperature.
Q 38.
(a) What is a physical change ? Give two examples of physical changes.
(b) What is a chemical change ? Give two examples of chemical changes.
Q 39.
What are non-aqueous solutions?
Q 40.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 41.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 42.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 43.
Is air a mixture or a compound ? Give three reasons for your answer.
Q 44.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 45.
Name the process you would use to separate a mixture of water and alcohol.
Q 46.
How would you separate a mixture of sugar and salt ?
Q 47.
What are different categories of pure substance?
Q 48.
What is a compound? Give an example.
Q 49.
Why do fish go in deep waters during day light?
Q 50.
How are sol, solution and suspension different from each other?
