Question:
Describe sieving method.
Answer:
When the sizes of the components of a mixture are big enough, they can be separated with the help of sieve. A sieve is a simple mechanical device in which a mesh is attached to a frame. When the mixture is placed on the mesh and is stirred, particles of smaller size pass through the mesh while the bigger particles of the other component remain above the mesh. E.g. gram can be separated wheat, sieving of sand at construction site etc.
Is Matter Around Us Pure?
Q 1.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 2.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 3.
What are different ways to separate solid mixtures?
Q 4.
(a) What is meant by (i) elements (ii) compounds, and (iii) mixtures ? Write down the names of two elements,two compounds and two mixtures.
(b) Classify the following into elements,
compounds and mixtures :
Marble,
Air,
Gold,
Brass,
Sand,
Diamond,
Graphite,
Petroleum,
Common salt,
Sea-water,
Chalk
Q 5.
What is the general name of the process by which tea-leaves are separated from prepared tea ?
Q 6.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 7.
Define a compound. Give two points of evidence to show that sodium chloride is a compound.
Q 8.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 9.
What are the properties of a colloid?
Q 10.
Name any two solid substances whose mixture can be separated by sublimation.
Q 11.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 12.
Name the elements are in liquid state at room temperature.
Q 13.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 14.
Name the process by which the various gases of the air are separated.
Q 15.
What is meant by a pure substance?
Q 16.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 17.
What are the various methods to express concentration of a solution?
Q 18.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 19.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 20.
Name the process which is used in milk dairies to separate cream from milk.
Q 21.
What are the kinds of mixture?
Q 22.
Why do fish go in deep waters during day light?
Q 23.
What are the advantages of preparing solutions?
Q 24.
In beaker A, sugar cubes are dissolved into water while in beaker B, crushed cubes are taken. In which beaker the rate of dissolution is faster?
Q 25.
Name one pair of liquids which can be separated by using a separating funnel.
Q 26.
What are the properties of suspensions?
Q 27.
How crystallization is better than evaporation?
Q 28.
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 29.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 30.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 31.
Name a non-metal which is a good conductor of electricity.
Q 32.
What is the difference between solutions and colloids ?
Q 33.
On the basis of composition, how matter is classified?
Q 34.
What are different categories of pure substance?
Q 35.
Alloys cannot be separated by physical means, though it is considered mixture, Why?
Q 36.
Why air is a mixture not a compound? Give reasons.
Q 37.
Explain with an example what is a colloid?
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.
What principle is applied in centrifugation? Give examples where this method is applied to separate mixtures.
Q 40.
A good method to separate alum (phitkari) from impure samples is
(a) Filtration
(b) Sedimentaion
(c) Crystallization
(d) Sublimation
Q 41.
How many elements are there which are in gaseous state at room temperature?
Q 42.
Who used the term 'element' first time?
Q 43.
What are the differences and similarities between concentration and solubility?
Q 44.
Give examples of liquids that are
(i) completely miscible
(ii) partially miscible
(iii) practically immiscible
Q 45.
Is air a mixture or a compound ? Give three reasons for your answer.
Q 46.
Give two reasons for supposing that water is a compound and not a mixture.
Q 47.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 48.
A 5 per cent sugar solution means that:
(a)5 g of sugar is dissolved in 95 g of water.
(b)5 g of sugar is dissolved in 100 g of water.
Choose the correct answer.
Q 49.
What is difference between colloids and suspensions ?
Q 50.
Which of the following will show Tyndall effect ? Why ?
(a) Salt solution
(b) Starch solution
(c)Milk
