Question:
What are the characteristics exhibited by a pure substance?
Answer:
- A pure substance contains only one kind of atoms or molecules.
- It is perfectly homogenous
- It has definite composition which does not vary with time.
- It has definite melting point, boiling point, density 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.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 3.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 4.
What are the physical states of dispersed phase and dispersion medium of a fog?
Q 5.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 6.
Name the apparatus you would use to separate oil from water.
Q 7.
What is meant by solute and solvent?
Q 8.
What is saturated solution? Explain with an example.
Q 9.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 10.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 11.
Name one pair of liquids which can be separated by using a separating funnel.
Q 12.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 13.
Name the technique to separate
(i) butter from curd
(ii) salt from sea-water
(iii) camphor from salt
Q 14.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 15.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 16.
What is a solution? What are the properties of a solution?
Q 17.
What are non-aqueous solutions?
Q 18.
What is an unsaturated solution?
Q 19.
What are the various methods to express concentration of a solution?
Q 20.
Define Brownian movement in colloids.
Q 21.
What are the differences and similarities between concentration and solubility?
Q 22.
What is meant by saying that metals are malleable and ductile ?
Q 23.
What are pure substances ? Give two examples of pure substances.
Q 24.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 25.
Name one pair of substances whose mixture can be separated completely by distillation.
Q 26.
Name the elements are in liquid state at room temperature.
Q 27.
Name a metal which is soft and a non-metal which is hard.
Q 28.
Give two reasons for supposing that water is a compound and not a mixture.
Q 29.
Choose one term from the following which includes the other three :
aerosol,
emulsion,
colloid,
sol
Q 30.
What are different categories of pure substance?
Q 31.
What are the kinds of mixture?
Q 32.
Why do fish go in deep waters during day light?
Q 33.
What is Chromatography?
Q 34.
Name a non-metal which is a good conductor of electricity.
Q 35.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 36.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 37.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 38.
Name two properties of a substance to check its purity?
Q 39.
List the points of differences between homogeneous and heterogeneous mixtures.
Q 40.
What are suspensions? Explain with an example.
Q 41.
How crystallization is better than evaporation?
Q 42.
What is an emulsion? Give examples
Q 43.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 44.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 45.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 46.
State the differences between compounds and mixtures.
Q 47.
What are the properties of suspensions?
Q 48.
How many elements are there which are in gaseous state at room temperature?
Q 49.
Who used the term 'element' first time?
Q 50.
(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
