NCERT Solutions For Class 9 Science Chapter 2 Is Matter Around Us Pure
| 1. Exercise Questions |
| 2. Intext Questions |
NCERT Solutions For Class 9 Science Chapter 2 Is Matter Around Us Pure on this step-by-step answer guide . In some of State Boards and CBSE schools, students are taught thru NCERT books. As the chapter comes to an end, students are requested few questions in an exercising to evaluate their knowledge of the chapter. Students regularly want guidance dealing with those NCERT Solutions. It’s most effective natural to get stuck withinside the exercises while solving them so that you could assist students rating better marks, we have provided grade by grade NCERT answers for all exercises of Class 9 Science Is Matter Around Us Pure so you can be searching for assist from them. Students have to solve those exercises carefully as questions withinside the very last exams are requested from those so these exercises at once have an impact on students’ final score. Find all NCERT Solutions for Class nine Science Is Matter Around Us Pure below and prepare for your tests easily.
NCERT Solution for Class 9 Science – Chapter 2
Is Matter Around Us Pure?
Exercise Questions
Q. 1. Which separation techniques will 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 .
Ans . ( a ) Crystallization or evaporation .
( b ) Sublimation .
( c ) Centrifugation or sedimentation .
( d ) Chromatography .
( e ) Centrifugation .
( f ) Separating funnel .
( g ) Hand – picking .
( h ) Magnetic separation .
( i ) Winnowing .
( j ) Centrifugation .
Q. 2. Write the steps you would use for making tea . Use the words – solution , solvent , solute , dissolve , soluble , insoluble , filtrate and residue .
Ans . ( i ) Take the solvent , water , in a kettle . Heat it . When the solvent boils , add the solute , milk . Milk and water forms a solution .
( ii ) Then pour some tea leaves over a sieve . Pour slowly hot solution of milk over tea leaves . Colour of tea leaves goes into solution as filtrate . The remaining tea leaves being insoluble remains as residue .
( iii )Add requisite sugar which dissolves and the tea is ready .
Q. 3 . 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 ) .
( a ) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K ?
( b ) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature . What would she observe as the solution cools ? Explain .
( c ) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature ?
( d ) What is the effect of change of temperature on the solubility of a salt ?
Ans . ( a ) At 313 K , Potassium nitrate for saturated solution of 100 grams of water = 62 g
Potassium nitrate for saturated solution of 50 grams of water = 31 g
( b ) Some amount of dissolved potassium chloride will reappear as undissolved solid ‘ ( crystallisation ) ‘ as solubility of solute decreases with the decrease in temperature .
( c ) Solubility of each salt at 393 K are as follows :
1. Potassium nitrate 32
2. Sodium chloride 36
3. Potassium chloride 35
4. Ammonium chloride 37
Ammonium chloride salt has the highest solubility at this temperature .
( d ) Solubility of salt increases with the increase in temperature .
Q. 4. Explain the following giving examples .
( a ) Saturated solution ,
( b ) Pure substance ,
( c ) Colloid ,
( d ) Suspension .
Ans . ( a ) Saturated solution : A solution in which no more of the solid ( solute ) can be dissolved at a given temperature is called a saturated solution . Suppose 50 g of a solute is the maximum amount that can be dissolved in 100 g water at 298 K. Then 150 g of solution so obtained is the saturated solution at 298 K.
( b ) Pure substance : A pure substance consists of a single type of matter or particles and cannot be separated into other kind of matter by any physical process . Pure substances always have the same colour , taste and texture at a given temperature and pressure . For example , pure water is always colourless , odourless and tasteless and boils at 373 K at normal atmospheric pressure .
( c ) Colloid : Colloids are heterogeneous mixtures , the particle size is too small to be seen with a naked eye , but it is big enough to scatter light . The particles are called the dispersed phase and the medium in which they are distributed is called the dispersion medium . Colloids are useful in industry and daily life . A colloid has the following characteristics :
- It is a heterogeneous mixture .
- The size of particles of a colloid lies between 1 nm -100 nm and cannot be seen by naked eyes .
- The particles of colloid can scatter a beam of light passing through it and make the path visible .
- The particles of colloid cannot be separated from the mixture by filtration . The process of separation of colloidal particles is known as ‘ centrifugation ‘ .
- They do not settle down when left undisturbed . In other words , colloids are quite stable , e.g. smoke , milk , fog , cloud etc.
( 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 . A suspension has the following characteristics :
- It is a heterogeneous mixture .
- The size of particles of a suspension is greater than 100 nm and is visible to naked eyes .
- The particles of suspension can scatter a beam of light passing through it .
- The particles of a suspension settle down when left undisturbed .
- The particles of a suspension can be separated from its mixture by filtration . Eg . sand water .
Q. 5. Classify each of the following as a homogeneous or heterogeneous mixtures :
Soda water , wood , air , soil , vinegar and filtrated tea .
Ans . Homogeneous mixture : Soda water , air , vinegar , a filtrated tea .
Heterogeneous mixture : Wood , soil .
Q. 6. How would you confirm that a colourless liquid given to you is pure water ?
Ans . As we know every liquid has a specific boiling point at 1 atm ( atmospheric pressure ) . If the given colourless liquid boils exactly at 373 K at 1 atm , then it is pure water . If the boiling point is different , then the water is contaminated .
Q. 7. Which of the following materials fall in the category of a ‘ pure substance ‘ ?
( a ) Ice ( b ) Milk
( c ) Iron ( d ) Hydrochloric acid
( e ) Calcium oxide ( f ) Mercury
( g ) Brick ( h ) Wood
( i ) Air
Ans . Ice , Iron , Hydrochloric acid , Calcium oxide and Mercury are pure substances .
Q. 8. Identify the solutions among the following mixtures .
( a ) Soil ( b ) Sea water
( c ) Air ( d ) Coal
( e ) Soda water
Ans . Among the given mixtures following are the solutions :
( b ) Sea water , ( c ) Air and ( e ) Soda water .
Q.9 . Which of the following will show ” Tyndall effect ” ?
( a ) Salt solution
( b ) Milk
( c ) Copper sulphate solution
( d ) Starch solution .
Ans . Milk and starch solution show Tyndall effect because they are colloidal solution . Salt solution and copper sulphate solution are true solution . Their particle size is too small to scatter light . So they do not show Tyndall effect .
Q. 10. Classify the following into elements , compounds and mixtures :
( a ) Sodium ( b ) Soil
( c ) Sugar solution ( d ) Silver
( e ) Calcium carbonate ( f ) Tin
( g ) Silicon ( h ) Coal
( i ) Air ( j ) Soap
( k ) Methane ( l ) Carbon dioxide
( m ) Blood
Ans . Elements : Sodium , silver , tin , silicon .
Compounds : Calcium carbonate , methane , carbon dioxide .
Mixtures : Soil , sugar solution , coal , air , soap , blood .
Q. 11. Which of the following are chemical changes ?
( a ) Growth of a plant
( b ) Rusting of iron
( c ) Mixing of iron filings and sand
( d ) Cooking of food
( e ) Digestion of food
( f ) Freezing of water
( g ) Burning of a candle .
Ans . ( a ) Growth of a plant , ( b ) rusting of iron , ( d ) cooking of food , ( e ) digestion of food and ( g ) burning of a candle , show chemical changes .
Intext Questions
Page 15
Q. 1. What is meant by a substance ? [ NCERT Q. 1 , Page 15 ]
Ans . A material that consists of a single type of particles is known as pure substance . All constituent particles of pure substance have the same chemical nature .
Q. 2. List the points of differences between homogeneous and heterogeneous mixtures . [ NCERT Q. 2. Page 15 ]
Ans . A homogeneous mixture is a mixture having a uniform composition throughout the mixture . For example : Salt in water , sugar in water , copper sulphate in water .
A heterogeneous mixture is a mixture having a non – uniform composition throughout the mixture . For example : Sodium chloride and iron fillings , salt and sulphur , oil and water .
Page 18
Q. 3. Differentiate between homogeneous and heterogeneous mixtures with examples . [ NCERT Q. 1 , Page 18 ]
Ans .
Q. 4. How are sol, solution and suspension different from each other? [ NCERT Q. 2 , Page 18 ]
Ans.
Q. 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 . [ NCERT Q. 3 , Page 18 ]
Ans . Mass of solute ( sodium chloride ) = 36 g ( Given )
Mass of solvent ( water ) = 100 g ( Given )
Then , mass of solution = Mass of solute + Mass of solvent
Concentration of solution =
Page 24
Q. 6. 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 ? [ NCERT Q. 1 , Page 24 – I ]
Ans . A mixture of two miscible liquids kerosene and petrol having a difference in their boiling points more than 25 ° C can be separated by the method of distillation .
In this method , the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it . We also need a beaker , a water condenser and a bunsen burner . The apparatus is arranged as shown in the above figure . Then , the mixture is heated slowly . The thermometer should be watched simultaneously . Kerosene will vaporise and condense in the water condenser . The condensed kerosene is collected from the condenser outlet , whereas petrol is left behind in the distillation flask .
Q. 7 . Name the technique to separate :
( i ) Butter from curd
( ii ) Salt from sea – water
( iii ) Camphor from salt [ NCERT Q. 2 , Page 24 – I ]
Ans . ( i ) Butter can be separated from curd by centrifugation in which denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly .
( ii ) Salt can be separated from sea – water by evaporation in which as the water evaporates less and less water molecules are present to keep the salt particles apart . The salt therefore recrystallizes and can be collected .
( iii ) Camphor from salt can be separated by sublimation in which camphor sublimes directly converts to gas on heating leaving behind salt . Vapours of camphor solidifies and can be collected .
Q.8 . What type of mixtures is separated by the technique of crystallization ? [ NCERT Q. 3 , Page 24 – I ]
Ans . Crystallisation is a process that separates a pure solid in the form of its crystals from a solution , for example , salt obtained from sea is separated from impurities ; crystals of alum ( Phitkari ) are separated from impure samples .
Q. 9. Classify the following as chemical or physical changes :
( i ) cutting of trees ,
( ii ) melting of butter in a pan ,
( iii ) rusting of almirah ,
( iv ) boiling of water to form steam ,
( v ) passing of electric current , through water and the water breaking down into hydrogen and oxygen gases ,
( vi ) dissolving common salt in water ,
( vii ) making a fruit salad with raw fruits , and
( viii ) burning of paper and wood . [ NCERT Q. 1 , Page 24 – II ]
Ans . The physical change is the inter conversion of states because these changes occurs without a change in composition and no change in the chemical nature of the substance . Chemical change brings change in the chemical properties of matter and new substances are formed . A chemical change is also called a chemical reaction .
( i ) Cutting of trees → Physical change
( ii ) Melting of butter in a pan → Physical change
( iii ) Rusting of almirah → Chemical change
( iv ) Boiling of water to form steam → Physical change
( v ) Passing of electric current through water , and water breaking down into hydrogen and oxygen gas → Chemical change
( vi ) Dissolving common salt in water → Physical change
( vii ) Making a fruit salad with raw fruits → Physical change
( viii ) Burning of paper and wood → Chemical change
Q. 10. Try segregating the things around you as pure substances or mixtures . [ NCERT Q. 2 , Page 24 – II ]
Ans . Pure substance : Water , salt and sugar , etc. :
Mixture : Salt water , soil , wood , air , cold drink , rubber , sponge , fog , milk , butter , clothes and food .
Benefits of NCERT Solutions For Class 9 Science Chapter 2 Is Matter Around Us Pure
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