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.
What is the general name of the process by which tea-leaves are separated from prepared tea ?
Q 2.
What are the properties of a colloid?
Q 3.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 4.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 5.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 6.
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 7.
Name one pair of liquids which can be separated by using a separating funnel.
Q 8.
What is saturated solution? Explain with an example.
Q 9.
What is a solution? What are the properties of a solution?
Q 10.
What is meant by solute and solvent?
Q 11.
What is an unsaturated solution?
Q 12.
(a) What is meant by a solution ? Give two examples of solutions.
(b)What is a suspension ? Give two examples of suspensions.
(c)
Q 13.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 14.
What are the reasons for separating the constituents of a mixture?
Q 15.
Who gave the first explanatory definition of 'element'?
Q 16.
Name a metal which is soft and a non-metal which is hard.
Q 17.
(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 18.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 19.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 20.
What are aqueous solutions?
Q 21.
What are non-aqueous solutions?
Q 22.
What is Chromatography?
Q 23.
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 24.
Name a non-metal which is a good conductor of electricity.
Q 25.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 26.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 27.
Which of the following will show Tyndall effect ? Why ?
(a) Salt solution
(b) Starch solution
(c)Milk
Q 28.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 29.
Name the apparatus you would use to separate oil from water.
Q 30.
What are the characteristics exhibited by a pure substance?
Q 31.
What is meant by a pure substance?
Q 32.
Based on the type of solvent, how solutions are classified?
Q 33.
Based on the amount of solute in the given solution, how solutions are classified?
Q 34.
When we open the cap of a cola drink (or any carbonated beverage), why does excess of bubbles come out?
Q 35.
Why air is a mixture not a compound? Give reasons.
Q 36.
What are suspensions? Explain with an example.
Q 37.
What are the physical states of dispersed phase and dispersion medium of a cloud?
Q 38.
What are the various methods to express concentration of a solution?
Q 39.
What are different ways to separate solid mixtures?
Q 40.
Who used the term 'element' first time?
Q 41.
What is an emulsion? Give examples
Q 42.
State whether the following statement is true or false : Milk is a pure substance.
Q 43.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 44.
What are pure substances ? Give two examples of pure substances.
Q 45.
Give two reasons for supposing that water is a compound and not a mixture.
Q 46.
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 47.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 48.
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 49.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 50.
Name the process which can be used to separate a mixture of salt solution and sand.
