Question:
What principle is applied in centrifugation? Give examples where this method is applied to separate mixtures.
Answer:
Centrifugation works on the principle that that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly. Examples are:
- Separating cream from milk (cream comes as top layer)
- Used in diagnostic laboratories for blood and urine tests.
- Used in washing machines to squeeze out water from wet clothes.
- Used in preparing lactic cultures to prepare cheese (paneer) from milk in dairies.
Is Matter Around Us Pure?
Q 1.
What is the general name of the process by which tea-leaves are separated from prepared tea ?
Q 2.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 3.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 4.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 5.
Name any two solid substances whose mixture can be separated by sublimation.
Q 6.
What are the properties of a colloid?
Q 7.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 8.
What is meant by solute and solvent?
Q 9.
What are aqueous solutions?
Q 10.
What is saturated solution? Explain with an example.
Q 11.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 12.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 13.
What is a solution? What are the properties of a solution?
Q 14.
What are pure substances ? Give two examples of pure substances.
Q 15.
On the basis of composition, how matter is classified?
Q 16.
What are suspensions? Explain with an example.
Q 17.
A solution contains 40 mL of ethyl alcohol mixed with 100mL of water. What is the concentration of the solution in terms of volume by volume percentage?
Q 18.
How crystallization is better than evaporation?
Q 19.
Name one pair of liquids which can be separated by using a separating funnel.
Q 20.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 22.
When we open the cap of a cola drink (or any carbonated beverage), why does excess of bubbles come out?
Q 23.
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 24.
What are the reasons for separating the constituents of a mixture?
Q 25.
Define Brownian movement in colloids.
Q 26.
Name the following :
(a) a lustrous liquid metal.
(b) a liquid non-metal
(c) a metal which can be cut with a knife
(d) a non-metal which is good conductor of electricity.
(e) an element which melts when kept on the palm.
(f) the best conductor of heat.
Q 27.
What is an emulsion? Give examples
Q 28.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 29.
Fill in the following blanks :
(a)Milk is a.........solution but vinegar is a.......solution.
(b)A colloid is a........mixture and its components can be separated by the technique known as........
Q 30.
Name two properties of a substance to check its purity?
Q 31.
What are the constituents of brass?
Q 32.
State the differences between compounds and mixtures.
Q 33.
Why air is a mixture not a compound? Give reasons.
Q 34.
What is an unsaturated solution?
Q 35.
Explain with an example what is a colloid?
Q 36.
What principle is applied in centrifugation? Give examples where this method is applied to separate mixtures.
Q 37.
What is Chromatography?
Q 38.
Give two reasons for supposing that water is a compound and not a mixture.
Q 39.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 40.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 41.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 42.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 43.
(a) Name the process by which common salt is obtained from sea-water.
(b) Name the process by which common salt is purified.
Q 44.
How will you separate iron pins from sand ?
Q 45.
What are the characteristics exhibited by a pure substance?
Q 46.
What are the kinds of mixture?
Q 47.
What are non-aqueous solutions?
Q 48.
How are sol, solution and suspension different from each other?
Q 49.
What do you mean by strength of the solution?
Q 50.
What are the various methods to express concentration of a solution?
