NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure

NCERT Solutions for Is Matter Around Us Pure Class 9 Science is provided here at SimplyAcad to help students gain in-depth knowledge of the different components present in the chapter. The study materials prove helpful for students willing to strengthen their basics and transform their grades into highest scores. Students can use the solutions as guides to make comprehensive notes on it and learn how to approach different questions asked in the paper. Scroll below to access the NCERT solutions of Is Matter Around Us Pure and remember to practise it daily to better results.

Access the NCERT Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure

Question 1. What is meant by a substance?

Solution : 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.

Question 2. List the points of differences between homogeneous and heterogeneous mixtures.
Solution :

Question 3. Differentiate between homogeneous and heterogeneous mixtures with examples.

Solution :

Question 4. How are sol, solution and suspension different from each other?
Solution :

Question 5. 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.
Solution :

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

= 26.47 %

Question 6. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than), which are miscible with each other?

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

Question 7. Name the technique to separate
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.

Solution :

(i) centrifugation method.

(ii) evaporation method.

(iii) sublimation method.

Question 8. What type of mixtures are separated by the technique of crystallisation?
Solution : 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.

Question 9. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

Solution : 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.

Question 10. Classify the following as chemical or physical changes :
• cutting of trees,
• melting of butter in a pan,
• rusting of almirah,
• boiling of water to form steam,
• passing of electric current, through water and the water breaking down into hydrogen and oxygen gases,
• dissolving common salt in water,
• making a fruit salad with raw fruits, and
• burning of paper and wood.

Solution :
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

Question 11. Try segregating the things around you as pure substances or mixtures.
Solution :
Pure substance: Water, salt, sugar

Mixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food

Question 12. Which separation techniques will you apply for the separation of the following?
(a) Sodium chloride from its solution in water.
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(c) Small pieces of metal in the engine oil of a car.
(d) Different pigments from an extract of flower petals.
(e) Butter from curd.
(f) Oil from water.
(g) Tea leaves from tea.
(h) Iron pins from sand.
(i) Wheat grains from husk.
(j) Fine mud particles suspended in water.

Solution :
(a) Evaporation

(b) Sublimation

(c) Filtration

(d) Chromatography

(e) Centrifugation

(f) Separating funnel

(g) Filtration

(h) Magnetic separation

(i) Winnowing/ sedimentation

(j) Decantation and filtration

Ques 13- How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25° C) which are miscible with each other? \textbf

{Solution:} The components of a mixture containing two miscible liquids, i.e., kerosene and petrol, can be separated by distillation, as it is given that the difference in their boiling points is significant. \textbf{Boiling point of kerosene:} approximately \ \textbf{Boiling point of petrol:} \textbf{Miscible liquids:} A mixture of two or more liquids that intermix with each other to form a homogeneous solution. Example: mixture of ethanol and water. \textbf{Distillation:} It is a technique for separating a mixture of two miscible liquids that boil without decomposing (as that would change the substance to be separated) and have a sufficient difference in boiling points (i.e., more than 25 K). \textbf{Principle involved in the separation of mixture:} The component with the lower boiling point evaporates first and leaves the mixture due to the sufficient difference in their boiling points. \textbf{Set-up for the distillation:} \begin{itemize} \item Mixture of kerosene and petrol is poured into a round-bottom flask held by a clamp and placed on the water bath on a burner. \item The mouth of the round-bottom flask is fitted with a thermometer and a water condenser called Liebig’s condenser. \item The inner tube of the condenser is connected to the flask for the liquid to pass through, and cool water is circulated through its outer tube to condense the vapors coming from the round-bottom flask. \item An empty measuring cylinder is placed at the other end of the condenser to collect the liquid. \end{itemize} \textbf{Process of distillation:} \begin{enumerate} \item The mixture is heated gradually. \item Petrol begins to form vapors as the

boiling point of petrol is attained first. \item The vapors of petrol condense when passed through the condenser and are collected in the measuring flask. \item Kerosene remains behind in the round-bottom flask as it has a higher boiling point.

Question 14. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below( results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).