Chemistry

Is Matter Around Us Pure?

Question:

What are the characteristics of mixture?

Answer:

1. Variable composition: The constituents of a mixture are present in any ratio. Example: A mixture of sand and salt can be in a ratio of 1:2 or 1:3 by weight.
2. Only Physical change: The mixture is a result of physical change. The constituents of a mixture do not bind each other by chemical bonds. Example: In air the main constituents, i.e., oxygen, nitrogen and carbon dioxide, do not bind each other with chemical bonds.
3. No specific properties: The properties of a mixture are the average of the properties of its constituents. Example: The properties of air are average common properties of nitrogen and oxygen.
4. Homogeneity: Most of the mixtures are heterogeneous, i.e., their constituents are not spread evenly throughout. However, some mixtures are homogeneous i.e. constituents are uniformly spread out. Example: In the mixture of iron and sulphur, at some places iron is more and at some places sulphur is more.
5. Separation Methods: In general, the constituents of mixture can be separated by applying suitable physical methods. E.g. Iron can be separated from the mixture of iron and sulphur with the help of a magnet.
6. Energy changes: In general, no energy is released or absorbed during the formation of a mixture. Example: On mixing iron and sulphur, heat energy is neither absorbed nor evolved.
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Is Matter Around Us Pure?

Q 1.

State the differences between compounds and mixtures.

Q 2.

What are the differences and similarities between concentration and solubility?

Q 3.

Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass

Q 4.

What is a solution? What are the properties of a solution?

Q 5.

What are the characteristics exhibited by a pure substance?

Q 6.

What are the properties of suspensions?

Q 7.

Name two properties of a substance to check its purity?

Q 8.

What factors affect the solubility of solvent and solute?

Q 9.

What is meant by a pure substance?

Q 10.

What are the reasons for separating the constituents of a mixture?

Q 11.

What are suspensions? Explain with an example.

Q 12.

What are the physical states of dispersed phase and dispersion medium of a fog?

Q 13.

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 14.

How crystallization is better than evaporation?

Q 15.

Define mixture.

Q 16.

Why air is a mixture not a compound? Give reasons.

Q 17.

What are the advantages of preparing solutions?

Q 18.

Name the elements are in liquid state at room temperature.

Q 19.

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.

What are the characteristics of mixture?

Q 27.

What is meant by Solubility?

Q 28.

Is air a mixture or a compound ? Give three reasons for your answer.

Q 29.

(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 30.

How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?

Q 31.

Name the process you would use to separate a mixture of two miscible liquids (like acetone and water).

Q 32.

Name one pair of substances whose mixture can be separated completely by distillation.

Q 33.

How will you separate iron pins from sand ?

Q 34.

What are the various methods to express concentration of a solution?

Q 35.

Name the technique to separate
(i) butter from curd
(ii) salt from sea-water
(iii) camphor from salt

Q 36.

Give examples of liquids that are
(i) completely miscible
(ii) partially miscible
(iii) practically immiscible

Q 37.

Name a non-metal which is a good conductor of electricity.

Q 38.

State three reasons why you think air is a mixture and water is a compound.

Q 39.

Winnowing works on what property?

Q 40.

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 41.

Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar

Q 42.

Name a metal which is soft and a non-metal which is hard.

Q 43.

Which of the following will show Tyndall effect ? Why ?
(a) Salt solution
(b) Starch solution
(c)Milk

Q 44.

21.5 g of sodium chloride dissolves in 60 g of water at 25°C. Calculate the solut water at that temperature.

Q 45.

State whether the following statements are true or false :
(a) Alcohol can be separated from a mixture of alcohol and water by a separating funnel.
(b) Salt and water can be recovered from an aqueous salt solution by the process of evaporation.

Q 46.

Name the process by which the various gases of the air are separated.

Q 47.

(a) Name the process by which all the dye can be recovered from black ink.
(b) Name the process by which the various dyes' (coloured materials) present in black ink can be separated.

Q 48.

Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?

Q 49.

What difference in the properties of common salt and sand would enable you to separate a mixture of these two substances ?

Q 50.

How would you separate a mixture of sugar and salt ?