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Is Matter Around Us Pure

In the previous chapter we had discussed matters. In this chapter we will explore more about pure substance and mixture. What are their properties, how different mixtures of substance can be separated what makes them together.

Download pdf of NCERT Solutions for Class science Chapter 2 Is Matter Around Us Pure

Download pdf of NCERT Examplar with Solutions for Class science Chapter 2 Is Matter Around Us Pure

Exercise 1

  • Q1

    What is meant by a pure substance?

    Ans:

    The substances which are formed by only one kind of particles and having a constant composition of chemicals and characteristic properties throughout the sample.


    Q2

    List the points of differences between homogeneous and heterogeneous mixtures.

    Ans:

    Mixtures are formed when two or more pure substances are mined together, for example : salt , solution ,air etc.

    Types of mixture :

    i). Homogenous mixture    ii). Heterogenous mixture
     

    i). Homogeneous mixture :

    1. A homogenous mixture has a uniform composition throughout its mass.

    2. The constituents of a homogeneous mixture cannot be seen easily.

    3. Homogeneous mixture has no visible boundaries of separation between its constituents. E.g : salt solution.

    ii). Heterogeneous mixture :

    1. A heterogeneous, minture does not have a uniform composition throughout its mass.

    2. The constituents of heterogeneous mixture can usually be seen easily.

    3. Heterogeneous mixture has visible boundaries of respiration between the various constituents. e.g.: oil water mixture.


Exercise 2

  • Q1

    Differentiate between homogeneous and heterogeneous mixtures with examples.

    Ans:
    Homogenous Mixture Heterogeneous Mixture

    1. It has uniform composition properties.

    2. The substances are completely mixed.

    3. There is no bible boundary of separation.

    4. All homogenous mixtures are called solution.

    5. Its particle can not be seen with naked eye.
    e.g. - Sea - water, alcohol, salt solution etc.

    1. It has non-uniform composition properties.

    2. The substances remain separate.

    3. There is a visible boundary of separation.

    4. All the suspensions are colloids are heterogeneous.

    5. Its particle can be seen with naked eye.
    e.g. - oil - water chalk water.

     


    Q2

    How are sol, solution and suspension different from each other?

    Ans:

    Sol :

    1. It is a heterogeneous mixture.

    2. Its particle is too small to be seen by naked eye.

    3. They scatter a beam of light.

    4. Particles cannot be separated by filtration to and sedimentation.

    Solution :    

    1. It is a homogeneous mixture. 

    2. Its particles are smaller than Inm, they are not visible to naked eye.

    3. They do not scatter a beam of light.

    4. Particles cannot be reported by filtration and sedimentation.

    Suspension :

    1. It is a heterogeneous mixture.

    2. Its particles are visible to a naked eye.

    3. They scatter a beam of light.

    4. Particles can be separated.


    Q3

    To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.

    Ans:

    Mass of solute ( NaCl ) = 36 gn

    Mass of solvent (water) = 100 gm 

    Total mass of solution = mass of solute + mass of solvent

    = 36 + 100
    = 136 gm


Exercise 3

Exercise 4

Exercise 5

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