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.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 3.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 4.
Name one pair of liquids which can be separated by using a separating funnel.
Q 5.
What is meant by saying that metals are malleable and ductile ?
Q 6.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 7.
What is saturated solution? Explain with an example.
Q 8.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 9.
Define Brownian movement in colloids.
Q 10.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 11.
What is an emulsion? Give examples
Q 12.
Give two reasons for supposing that water is a compound and not a mixture.
Q 13.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 14.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 15.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 16.
What are non-aqueous solutions?
Q 17.
What is an unsaturated solution?
Q 18.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 19.
Name a non-metal which is a good conductor of electricity.
Q 20.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 21.
On the basis of composition, how matter is classified?
Q 22.
What are different categories of pure substance?
Q 23.
Explain with an example what is a colloid?
Q 24.
What are the reasons for separating the constituents of a mixture?
Q 25.
State whether the following statement is true or false : Milk is a pure substance.
Q 26.
What are pure substances ? Give two examples of pure substances.
Q 27.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 28.
What is meant by solute and solvent?
Q 29.
How are sol, solution and suspension different from each other?
Q 30.
What are different ways to separate solid mixtures?
Q 31.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 32.
Which of the following will show Tyndall effect ? Why ?
(a) Salt solution
(b) Starch solution
(c)Milk
Q 33.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 34.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 35.
What are the kinds of mixture?
Q 36.
What is a solution? What are the properties of a solution?
Q 37.
What are suspensions? Explain with an example.
Q 38.
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 39.
Name the technique to separate
(i) butter from curd
(ii) salt from sea-water
(iii) camphor from salt
Q 40.
Give examples of liquids that are
(i) completely miscible
(ii) partially miscible
(iii) practically immiscible
Q 41.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 42.
Name any two solid substances whose mixture can be separated by sublimation.
Q 43.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 44.
How will you separate a mixture of chalk powder and water ?
Q 45.
What are the constituents of brass?
Q 46.
State the differences between compounds and mixtures.
Q 47.
What do you mean by strength of the solution?
Q 48.
What are the various methods to express concentration of a solution?
Q 49.
How many elements are there which are in gaseous state at room temperature?
Q 50.
Who gave the first explanatory definition of 'element'?
