NCERT Grade 9-Is Matter Around Us Pure-Answers – MySchoolPage

NCERT Grade 9-Is Matter Around Us Pure-Answers

NCERT Solutions for Class 9 Science

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1.     (a) Evaporation method

(b) Sublimation method

(c) by heating and then after filtration

(d) by Chromatography

(e) by method of centrifugation

(f) by using separating funnel

(g) by filtration method using strainer

(h) with the help of a magnet

(i) by winnowing

(j) by centrifugation

2.    Take more amount of solvent (water) in a pan and after heating it add little amount of solute (sugar) to the solvent. Solute will dissolve completely in the solvent forming true solution, then add tea leaves that are insoluble along with another soluble liquid milk. After boiling allow filtration with a sieve so the filtrate you obtain is tea while the residue has tea leaves that are thrown away.

3.    (a) At 313 K temperature the amount of potassium nitrate required was 62g in 100ml of water so in 50g water we will need to dissolve = 62 X 50/100= 31g potassium nitrate.

(b) At 373K saturated solution preparation needs 54g potassium nitrate and at room temperature (293 K) saturation solution formation occurs with 35g potassium nitrate hence = 54 – 35 = 19g potassium nitrate will precipitate out as undissolved salt.

(c) Solubilities are (in 100mg of water) 32,36,35,37 respectively for the
mentioned salts and the highest solubility is of ammonium chloride at this temperature.

(d) Solubility of salts is directly proportional to the temperature i.e. if temperature increases then solubility will increase and if the temperature decreases solubility will also decrease.

4.    (a) Saturated solution: It is a solution in which no more solute particles can be dissolved at a particular temperature.

(b) Pure substance: Such substance that has a uniform composition i.e. has particles with identical properties is called pure substance eg sugar, salt, water, nitrogen etc.

(c) Colloid: It is a kind of heterogeneous mixture/solution in which particle size is between 1nm and 1000nm. Colloids have dispersion medium and dispersed phase.eg smoke, milk, shaving cream, jelly, cheese etc.

(d) Suspension: It is a kind of heterogeneous mixture in which insoluble solid particles remain suspended in the medium and dispersion particles are visible to the unaided eyes. eg muddy river water, chalk powder in water, dust storm, sand in water etc.

5.    Homogeneous mixture                                 Heterogeneous mixture

Soda water, air, vinegar, filtered tea.                           Wood, soil.

6.    If we allow the given liquid to evaporate by heating it as in a clean china dish so:

(a) any residue remaining in the china dish will indicate that water is not pure
but contains impurities.

(b) no residue in china dish will indicate that water is pure.

7.    Pure substances are: ice, iron, hydrochloric acid, calcium oxide, mercury.

8.    Sea water, air and soda water are solutions.

9.    Milk and starch solution have larger particles since they are not true solutions so
they will show tyndall effect.

10.  Elements                          Compounds                            Mixture

Sodium                             Calcium carbonate                Soil

Silver                                 Soap                                         Sugar solution

Silicon                               Methane                                  Air

Tin                                     Carbon dioxide                      Blood

Coal

11.  Rusting of iron, cooking of food, digestion of food, burning of a candle are chemical changes.

12.  Substance can be defined as that kind of matter where constituent particles cannot be separated from each other by any physical process since they are all similar in chemical properties.

13.  Homogeneous mixture

(i) They have uniform composition throughout the mixture.

(ii) Their components cannot be separated by filtration but separation takes place be distillation method only.

(iii) examples are salt & water mixture, sugar & water mixture.

Heterogeneous mixture

(i) They do not have a uniform composition throughout the mixture.

(ii) Their components can be separated by filtration method.

(iii) examples are a mixture of sulphur powder and iron fillings, kerosene oil and water.

14.  Homogeneous mixture

(i) They have uniform composition throughout the mixture.

(ii) Their components cannot be separated by filtration but separation takes place be distillation method only.

(iii) examples are salt & water mixture, sugar & water mixture.

Heterogeneous mixture

(i) They do not have a uniform composition throughout the mixture.

(ii) Their components can be separated by filtration method.

(iii) examples are a mixture of sulphur powder and iron fillings, kerosene oil and water.

15.  Sol=kind of colloidal solution

(i) It has dispersed phase and dispersion phase.

(ii) It appears homogeneous but is heterogeneous.

(iii) Particles are visible with the help of electron microscope.

(iv) Particle size is 10-7 to 10-5 cm .

Eg. gold sol, milk of magnesia etc

Solution = True Solution

(i) It has soluble solute and solvent phase.

(ii) It is homogeneous.

(iii) Particles are not visible by all means.

(iv) Particle size is less than 10-7cm.

Eg sugar solution, salt solution

Suspension

(i) It has insoluble solute suspended in the solvent medium.

(ii) It is heterogeneous.

(iii) Particles are visible by naked eyes.

(iv) Particles size is more than 10-5 cm.

Eg muddy river water, dust storm.

16.  Mass of sodium chloride (solute) = 36 g

Mass of water (solvent) = 100 g

Mass of solution = 36 + 100 = 136 g

Therefore, concentration percentage = mass of solute/mass of solution × 100

= 36/136 × 100

= 26.47 %.

17.  We can separate a mixture containing kerosene and petrol by distillation technique since difference in their boiling points is more than 25°C. So through distillation we can get them separated.

18.  (i) centrifugation method.

(ii) evaporation method.

(iii) sublimation method.

19.  From impure samples of solids, pure solid crystals can be obtained by the method of crystallization for eg to obtain pure sugar from impure sample of the same.

20.  cutting of trees = chemical change

melting of butter in a pan = physical change

rusting of almirah = chemical change

boiling of water to form steam = physical change

passing of electric current, through water and the water breaking down into

hydrogen and oxygen gases = chemical change

dissolving common salt in water = physical change

making a fruit salad with raw fruits = physical change

burning of paper and wood = chemical change

21.  You can do it by yourself like try mixing chalk powder and water then separate them.

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