The NCERT questions given at the end of each chapter are not only important for examinations but also helpful to clearly understand all the concepts. That is why students are strongly recommended to read NCERT books thoroughly, make appropriate notes on each chapter and solve the exercise questions. Solving the NCERT exercise questions gives you enough practice to solve any other problem asked in the exams. This will help you assure positive results.
Here we are providing NCERT solutions for CBSE Class 9 Science Chapter 2 - Is Matter Around Us Pure. All these solutions have been prepared by the subject experts and are a hundred percent accurate. Therefore, all those students who are having trouble finding the right and simple answers for questions given in Class 9 Science NCERT Chapter 2, can use the answers given here as referral answers.
Some of the questions and their solutions from NCERT Solutions for Class 9 Science Chapter - Is Matter Around Us Pure, are as follows:
Q. Name the technique to separate:
(i) Butter from curd
(ii) Salt from sea water
(iii) Camphor from salt
Sol. (i) By using centrifugation method, butter can be separated from curd.
(ii) By using evaporation method, salt from sea water can be separated. Water vaporizes on evaporation leaving behind the salt.
(iii) Camphor from salt can be separated by sublimation method. On subliming camphor.
Q. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Method of preparation of tea:
(i) Take some water (solvent) in a pan and heat it.
(ii) Add some sugar (solute) and boil to dissolve the sugar completely the obtained homogeneous mixture is called solution.
(iii) Add tea leaves (or tea) in the solution and boil the mixture.
(iv) Now add milk and boil again.
(v) Filter the mixture through the tea strainer and collect the filtrate or soluble substances, i.e. tea in a cup. The insoluble tea leaves left behind as residue in the strainer.
Q. Explain the following giving examples:
(a) Saturated solution
(b) Pure substance
(a) Saturated solution: A solution in which no more amount of solute can be dissolved at a particular temperature is called saturated solution, Example: when sugar is dissolved repeatedly in a given amount of water, a condition is reached at which further dissolution of sugar is not possible in that amount of water at room temperature.
(b) Pure substance: A substance made up of single type of particles (atoms and/or molecules) is called pure substance. All elements and compounds are said to be pure, Example: water, sugar etc.
(c) Colloid: A heterogeneous mixture in which the solute particle size is too small to be seen with the naked eye, but is big enough to scatter light is known as Colloid. There are two phases in colloidal solution:
Dispersed phase: Solute particles are said to be dispersed phase.
Dispersion medium: The medium in which solute particles are spread is called the dispersion medium. Example: Milk, clouds etc., are the example of colloid.
(d) Suspension A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye. Example: Mixture of sand, Water and Muddy water etc.
Q. Classify each of the following as a homogeneous or heterogeneous mixture. Soda water, wood, air, soil, vinegar, filtered tea
Sol. Homogeneous mixtures: Air, soda water, vinegar, filtered tea.
Heterogeneous mixtures: Wood, soil.
Q. How would you confirm that a colorless liquid given to you is pure water?
Sol. If the given colorless liquid boils at 100°C sharp, it is pure water, otherwise not.
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