CLASS IX REVISION
 1.Why water is a compound not a mixture?

Q 2 Which of the following will show properties of its constituents? Methane or soil

Q 3 Name solute in brass

Q 4 Particle size of a substance was 50 nm. Is it solution or colloid or suspension

Q 5 A solution is prepared by dissolving 12g of sodium chloride in 150 g of solution. Calculate the mass percentage of solution.

Q66(i)Name a soft metal.

   (ii)Name the element present in diamond.

  (iv) Name a non-metal having shining surface.

 (v)Name an element used as semi conductor  Between sulphur and copper which one you will use for making wire

(vi) Non-metals are bad conductors of electricity. Name a non metal which is conductor of electricity and is used in making electrodes.

6 A gas jar containing air is inverted over another containing NO2 gas which is brown in colour and heavier than air. After some time brown colour is seen in the inverted gas jar too. Identify the phenomenon associated with this observation. 

Ans. Diffusion

7 List four reasons to support that water is a compound and not a mixture.

Ans. (i) The composition of water is fixed. (H : O = 1 : 8, by mass)

        (ii) Melting point and boiling point of water is fixed.

        (iii) Water cannot be separated into its constituent elements by physical methods.

        (iv) Water has entirely different properties from those of its constituent elements hydrogen and oxygen

         

8 What is meant by (i) a solute and (ii) a solvent in a solution? Identify the solute and the solvent in a homogenous mixture of iodine and alcohol. 

9. A housewife churned full cream milk with a milk churner.

     (i) What did she observe after churning milk?

     (ii) What could be the possible reason for this observation? 

9.How can you distinguish between a salt solution and a pure liquid without tasting it?

Ans. On evaporation, a salt solution will leave a residue of salt, when all the liquid evaporates. A pure liquid leaves no residue on evaporation.What is a colloidal solution? How is it different from a true solution? Identify the colloidal solutions from the following : Copper sulphate solution, vinegar, blue ink, milk of magnesia.

Ans. A heterogeneous solution in which particle size is between 1nm to 100nm, such that the solute particles neither dissolve nor settle down in a solvent, is called a colloidal solution. But true  solution is a homogeneous solution in which particles cannot be seen under a microscope. Milk of magnesia is a colloidal solution

10.Classify the following into elements, compounds and mixtures: 

     i) Sodium ii) Soil

     iii) Tin iv) Calcium carbonate

11. Why naphthalene balls disappear with time without leaving any solid?