FULL FORM WITH DETAILS: NCERT SOLUTION CLASS 9 SCIENCE

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Tuesday, 7 April 2020

NCERT SOLUTION

CLASS 9

CHAPTER 2 IS MATTER AROUND US PURE

PAGE NO. 28 ,29 and 30

EXERCISES

QUESTION NO. 1

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 tea.

(i) Wheat grains from sand.

(j) Fine mud particles suspended in water.

ANSWER NO. 1

(a) Evaporation.
(b) Sublimation.
(c) By using a suitable filter.
(d) Chromatography.
(e) By centrifugal machine or churning the curd by hand.
(f) Decantation.
(g) Filtration.
(h) By the process of magnetic separation.
(i) By winnowing.
(j) Coagulation and decantation.
Alum is added to muddy water which makes the soil particles heavier and settle down in bottom. The clean water is then separated by decantation.

QUESTION NO. 2

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

ANSWER NO. 2

For making tea following steps are to be taken -
(i) Take 100ml of water as a solvent and boil it for few minute.
(ii) Add one tea spoon sugar, one tea spoon tea leaves and 50ml of milk as a solute.
(iii) Boil it for few minutes so that sugar will dissolve in solution as sugar is soluble in water.
(iv) Filter the solution in a cup. The insoluble tea leaves will be left behind as residue.

QUESTION NO. 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).

Substance Temperature in K
Dissolved 283 293 313 333 353
Solubility
Potassium nitrate 21 32 62 106 167
Sodium chloride 36 36 36 37 37
Potassium chloride 35 35 40 46 54
Ammonium chloride 24 37 41 55 66

(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?

ANSWER NO. 3

(a) The solubility of potassium nitrate at 313 K is 62gm. Hence 62gm of potassium nitrate is required to make a saturated solution of potassium nitrate in 100gm of water at 313 K.
So to make a saturated solution in 50gms of water the required potassium nitrate will be 62/2 = 31gm.

(b) When a saturated solution of potassium chloride at 353 K is left to cool, then the solid potassium chloride will gradually separate from the solution ( because the solubility decrease on cooling.)

(c) The solubility of different salts at 293 K is potassium nitrate 32gm, Sodium chloride 36gm, Potassium chloride 35gm and Ammonium chloride 37gm.
Ammonium chloride has the highest solubility ( 37gm) at this temperature of 293 K.

(d) According to the given data solubility of a salt increases on increasing the temperature.

QUESTION NO. 4

4.Explain the following giving examples.
(a)saturated solution
(b)pure substance
(c)colloid
(d)suspension

ANSWER NO. 4

(a) Saturated Solution : At a particular temperature, a solution that has dissolved as much solute as it is capable of dissolving, is said to be saturated solution. It is also defined as if no more solute can be dissolved in a solution at a given temperature, it is called saturated solution.

(b) Pure Substance : A pure substance consist of a particles which have same chemical nature. A pure substance consist of a single type of particles.

(c) Colloid : In colloid particles are uniformly spread throughout the solution. Because of smaller size of particles, the appears to be homogeneous. But colloidal solution is a heterogeneous mixture. Example : milk, blood.

(d) Suspension : A suspension is a heterogeneous mixture in which the solute prticles do not dissolve but remained suspended throughout the bulk of the medium. The particles of suspension are visible to the naked eyes.

QUESTION NO. 5

Classify each of the following as a homogeneous or
heterogeneous mixture.
soda water, wood, air, soil, vinegar, filtered tea.

ANSWER NO. 5

HOMOGENEOUS HETEROGENEOUS
MIXTURE MIXTURE
1. Soda Water 1. Wood
2. Vinegar 2. Air
3. Filtered Tea 3. Soil

QUESTION NO. 6

How would you confirm that a colourless liquid given to you is pure water?

ANSWER NO. 6

By checking the boiling temperature of the liquid it can confirmed that given water is pure or not. If it boils at 100 C it is said be pure. But if there is a decrease or increase in the boiling point, it confirms that water has added impurities.

QUESTION NO. 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.

ANSWER NO. 7

PURE SUBSTANCES

Iron
Ice
Mercury
Hydrochloric Acid
Calcium Oxide

QUESTION NO. 8

Identify the solutions among the following mixtures.
(a)Soil
(b)Sea water
(c)Air
(d)Coal
(e)Soda water.

ANSWER NO. 8

SOLUTIONS

Sea Water
Air
Soda Water

QUESTION NO. 9

Which of the following will show “Tyndall effect”?
(a)Salt solution
(b)Milk
(c)Copper sulphate solution
(d)Starch solution.

ANSWER NO. 9

Milk and starch solution from the above list of solution will show ˋˋ Tyndall effect ˋˋ .

QUESTION NO. 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

ANSWER NO. 10

COMPOUND MIXTURE
1. Calcium Carbonate 1. Soil
2. Carbon dioxide 2. Sugar Solution
3. Methane 3. Coal
4. Air
5. Blood
6. Soap

QUESTION NO. 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.

ANSWER NO. 11

CHEMICAL CHANGES

Growth of plants
Rusting of iron
Cooking of food
Digestion of food
Burning of a candle

Monday, 6 April 2020

NCERT SOLUTION

CLASS 9

CHAPTER 2 IS MATTER AROUND US PURE

PAGE NO. 24

QUESTION NO. 1

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.

ANSWER NO. 1

Cutting of trees is a physical change.
Melting of butter in a pan is a physical change.
Rusting of almirah is a chemical change.
Boiling of water to water to form a stream is a physical change.
Passing of electric current, through water and water breaking down into hydrogen and oxygen gases - chemical change.
Dissolving common salt in water - physical change.
Making fruit salad with raw fruits - physical.
Burning of paper and wood - chemical change.

QUESTION NO. 2

Try segregating the things around you as pure substances or mixtures.

ANSWER NO. 2

A pure substance is made up of only one type of atoms or molecules where as mixtures are made up of combination of different types of particles.

Some of the things around us are -

Wood, air, milk, tap water, sodium chloride, gold ornament, alcohol, vinegar, diamond, steel, ice cream, naphthalene balls, baking soda, graphite, salt solution, alum, kerosene oil, steam etc. out of these
Pure substances are -
Naphthalene balls, sodium chloride, distilled water, diamond, steam, alum, alcohol, graphite, baking soda.

MIXTURE

Tap water, milk, air, gold ornament, ice cream, steel, kerosene oil, salt solution, brass, vinegar, wood.
Km

NCERT SOLUTION CLASS 9 CHAPTER 2 (IS MATTER AROUND US PURE ) PAGE NO. 24

QUESTION NO. 1

How will you separate a mixture containing kerosene and petrol ( difference between their boiling points is more than 25 C ), which are miscible with each other ?

ANSWER NO. 1

Simple distillation can be done when the temperature difference between the boiling point of two miscible liquids is at least 25 C. The temperature difference between the boiling points of petrol and kerosene in 25 C. So, this mixture can be separated using simple distillation.

In this method, The mixture of kerosene and petrol is taken in a distillation flash with a thermometer fitted in it to monitor the temperature. Apart from this a beaker, a water condenser and a Bunsen burner is also required. The mixture is heated slowly. Temperature should be monitored constantly. Kerosene will vaporize and condense in the water condenser. The condensed kerosene is collected from the condenser outlet whereas petrol is remained in the distillation flask.

QUESTION NO. 2

Name the technique to separate

(i) butter from curd,

(ii) salt from sea water,

(iii) camphor from salt.

ANSWER NO. 2

(i) Butter is separated from the curd by using centrifugation method.

(ii) Salt is separated from sea water by the method of crystallization or by the evaporation.

(iii) Camphor is separated from salt by sublimation technique.

QUESTION NO. 3

What type of mixtures are separated by the technique of crystallization ?

ANSWER NO. 3

Crystallisation is a process that separates a pure solid in the form of its crystals from a solution so it is used to separate a solid - liquid mixture.

NCERT SOLUTION CLASS 9 CHAPTER 2 (IS MATTER AROUND US PURE ) PAGE NO. 18

QUESTION NO. 1

Differentiate between homogeneous and heterogeneous mixtures with examples.

ANSWER NO. 1

HOMOGENEOUS MIXTURE

Particles are uniformly distributed throughout the mixture.
It has a uniform composition.
Components cannot be separated easily.
Example - Solution of sugar and alloys.

HETEROGENEOUS MIXTURE

All the particles are completely mixed and can be distinguished with the eye or under a microscope.
It has a irregular composition.
Components can be separated easily.
Example - Mixture of sand and common salt, mixture of sand and water.

QUESTION NO. 2

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

ANSWER NO. 2

A sol is a heterogeneous mixture which contain physically distinct parts and have non - uniform composition.

A solution is a homogeneous mixture of two or more substances.

A suspension is a heterogenous mixture in which the solute particles do not dissolve but remain suspended throughout the bulb of the medium.

QUESTION NO. 3

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

ANSWER NO. 3

Mass of solute = 36g
Mass of solvent = 100g

Mass of solution = 100+36 = 136g
Concentration of solution = Mass of solute X 100
Mass of solution
= 36 X 100
136
= 26.47%

NCERT SOLUTION CLASS 9 CHAPTER 2 (IS MATTER AROUND US PURE ) PAGE NO. 15

QUESTION NO. 1

What is meant by substance ?

ANSWER NO. 1

A pure substance consist of single type of particle. It is a pure single form of matter. It has definite properties and composition. Example - Iron.

QUESTION NO. 2

List the points of differences between homogeneous and heterogeneous mixtures.

ANSWER NO. 2

HOMOGENEOUS MIXTURE

Particles are uniformly distributed throughout the mixture.
It has a uniform composition.
Components cannot be separated easily.
Example - Solution of sugar and alloys.

HETEROGENEOUS MIXTURE

All the particles are completely mixed and can be distinguished with the eye or under a microscope.
It has a irregular composition.
Components can be separated easily.
Example - Mixture of sand and common salt, mixture of sand and water.

Saturday, 4 April 2020

NCERT SOLUTION CLASS 9 SCIENCE PAGE-6

NCERT SOLUTION OF CHAPTER 1 OF CBSE BOARD CLASS 9 ( MATTER IN OUR SURROUNDINGS)

PAGE NO 6

QUESTION NO 1

The mass per unit volume of a substance is called density. (density= mass/volume). Arrange the following in order of increasing density- air,exhaust from chimneys,honey,water,chalk,cotton and iron.

ANSWER;

In the given substances,the increasing order of their density as follows
1. Air.
2. Exhaust from chimney.
3. Cotton
4. Water
5.Honey
6. Chalk
7. Iron

QUESTION NO 2 (a)

Tabulate the differences in the characteristics of states of matter.

(b) Comment upon the following: rigidity,compressibility,fluidity,shape,kinetic energy and density.

ANSWER;

The differences in the characteristics of the matter are given in the following table-

Solid State Liquid State Gaseous State

1. Solid has definite 1.No definite 1.Gases have neither

shape and volume shape a definite shape nor

a definite volume.

2. Incompressible 2.Compressible 2.Highly compressible
3.There is a little 3.Liquid particles 3.The space between

space between the have a greater gas particles is the

particles of solid space compare to greatest

solid

4.The force of 4.The force of 4.The force of

attraction among attraction among attraction is least

the solid particles liquid particles are between the gaseous
are higher less than solid particles
5.Particles of solid 5.Particles of liquid 5.Gaseous particles
cannot move move freely are in a continuous
freely random motion

Answer 2 (b)

Rigidity------- It can be expressed as the tendency of matter to resist a change in shape.

Compressibility------ It is the ability to reduce to a lower volume when force is applied.

Fluidity ------ It is the ability to flow.

By Filling a gas container---------

Shape------ It defines a definite boundary.

Kinetic Energy-------- It is the energy of a particle due to its motion.

Density---------- It is the mass per unit volume.

QUESTION NO 3. Give Reasons---

(a) A gas fills completely the vessel in which it is kept.
(b) A gas exerts pressure on the walls of the container.
(c) A wooden table should be called a solid.
(d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.

ANSWER:

(a) There is less attraction between particles of gas. Thus gas particles move freely in all directions. Hence gas completely fills the vessel in which it is kept.

(b) Particles of gas move randomly in all directions at high speed. As a result, the particles collide each other and also collide with the walls of container with a force. Hence gas exerts pressure on the walls of the container.

(c) A wooden table has a definite shape and volume. It is rigid and cannot be compressed so it has the characteristics of a solid. So it is called solid.

(d) Particles of air have large spaces between them. That's why we can easily move our hand in air. while wood has little space between the particles. It is rigid also. Because of this reason we need a karate expert to move our hand,because more force is required.

QUESTION NO 4

Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.

ANSWER :

In the solid state, when water molecules come close to each other, the molecules are forced to align in a very particular structure a hexagonal lattice. It is tiny pores in which air is present. Due to increased bond angles and expanded molecular structure this implies greater volume and hence it has lower density.

Density = Mass/Volume

This is the reason why ice floats on water.

Thursday, 2 April 2020

NCERT SOLUTION CLASS 9 SCIENCE PAGE-10

NCERT SOLUTION OF CHAPTER 1 OF CBSE BOARD CLASS 9 ( MATTER IN OUR SURROUNDINGS)

PAGE NO 10

QUESTION NO 1

Why does a desert cooler cool better on a hot dry day?

ANSWER NO 1

PRINCIPLE:

When a liquid evaporates, the particle of the liquid absorb energy from the surroundings to compensate the loss of energy during evaporation. This makes the surroundings cool.

In desert cooler, the water from inside the cooler evaporate. This lead to absorption of energy from the surroundings, hence it cools the surroundings. In hot dry day the amount of water vapour present in air less, thus water present inside the cooler evaporates more, hence cools the surroundings.

QUESTION NO 2

How does the water kept in an earthen pot (matka) become cool during summer?

ANSWER NO 2

There are some pores in an earthen pot through which the liquid inside the pot evaporates, hence the evaporated particle of the liquid absorb energy from the pot to compensate the loss of energy during evaporation. This evaporation makes the water inside the pot cool.

QUESTION NO 3

Why does our palm feel cold when we put some acetone or petrol or perfume on it?

ANSWER NO 3

When we put some acetone or perfume or petrol on our palm, it evaporates. During evaporation, particles of liquid absorb energy from the surrounding and the surface of the palm to compensate the loss of energy, making the palm cool.

QUESTION NO4

Why are we able to sip hot tea or milk faster from a saucer rather than a cup?

ANSWER NO 4

In a saucer the surface area of tea is greater than the cup.

Hence it evaporates faster in a saucer and cools the hot tea faster in compare to cup. Because of this reason we are able to sip hot tea or milk faster from a saucer than a cup.

QUESTION NO 5

What type of clothes should we wear in summer?

ANSWER NO 5

We should wear cotton clothes in summer. We sweat more in summer and cotton clothes are good absorber of water. It absorb sweat from the body and expose the liquid to the atmosphere and evaporation takes place. During evaporation, particles on the surface of the liquid gain energy from our body surface, making the body cool.

NCERT SOLUTION CLASS 9 SCIENCE EXERCISE

NCERT SOLUTION OF CHAPTER 1 OF CBSE BOARD CLASS 9 ( MATTER IN OUR SURROUNDINGS)

EXERCISE PAGE NO 12

QUESTION NO 1

Convert the following temperatures to the celsius scale.

(a) 293 K (b) 470 K

ANSWER

(a) 293 K = 293-273 = 20 degree centigrade

(b) 470 K = 470-273 = 197 degree centigrade

QUESTION NO 2

Convert the following temperatures to the kelvin scale.

(a) 25 degree centigrade

(b) 373 degree centigrade

ANSWER

(a) 25 degree centigrade = 25 + 273= 298 K

(b) 373 degree centigrade = 373+273 = 646 K

QUESTION NO 3

Give reason for following observation observations.

(a) Naphthalene balls disappear with time without leaving any solid.

(b) We can get the smell of perfume sitting several metres away.

ANSWER

(a) Naphthalene balls has the property of sublimation. Evaporation of naphthalene balls takes place easily and it disappear with time without leaving any solid.

(b) Gaseous particle have less intermolecular force hence they move rapidly. So perfume diffuse in air easily. That's why we can smell perfume sitting several meters away.

QUESTION NO 4

Arrange the following substances in increasing order of forces of attraction between the particles ----- water,sugar,oxygen

ANSWER

Oxygen,water,sugar

QUESTION NO 5

What is physical state of water at---

(a) 25 degree centigrade (b) 0 degree centigrade (c) 100 degree centigrade

ANSWER

(a) Liquid

(b) Solid and Liquid

(c) Liquid and Vapour

QUESTION NO 6

Give two reason to justify--------

(a) Water at room temperature is a liquid.
(b) An iron almirah is a solid at room temperature.

ANSWER --

(a) Water at room temperature is a liquid because it has fluidity and
(i) has definite volume
(ii) but no definite shape

(b) An iron almirah is a solid at room temperature because
(i) it is rigid
(ii) and has a definite shape

QUESTION NO 7

Why is ice at 273 K more effective in cooling than water at the same temperature?

ANSWER---

Ice at 273 K is less energetic than water at same temperature. Because at this temperature water contains latent heat of fusion. So it has less cooling effect.

QUESTION NO 8

What produces more severe burns,boiling water or steam?

ANSWER----

Steam produces more severe burns than boiling water. This is because of steam has more energy in he form of latent heat of vaporization.

QUESTION NO 9

Name A,B,C,D,E and F in the following diagram showing change in its state.

ANSWER----

A------- Melting

B------- Boiling

C------- Condensation

D------- Solidification

E------ Sublimation

F------- Sublimation

Tuesday, 31 March 2020

NCERT SOLUTION CLASS 9 SCIENCE PAGE-9

NCERT SOLUTION OF CHAPTER 1 OF CBSE BOARD CLASS 9 ( MATTER IN OUR SURROUNDINGS)

PAGE 9

QUESTION NO 1

Convert the following temperature to celsius scale ;

(a) 300 K (b) 573 K

ANSWER:

(A) 300K = (300-273) = 27 Degree centigrade.

(B) 573 K = (573-273) = 300 Degree centigrade.

QUESTION NO 2

What is the physical state of water at ;

(A) 250 Degree centigrade (B) 100 Degree Centigrade

ANSWER NO 2

(A) Water at 250 degree centigrade exists in gaseous state.

(B) At 100 degree centigrade water can exists in both liquid and gaseous form. At this temperature,after getting the heat equal to the latent heat of vaporization,water starts changing from liquid state to gaseous state.

QUESTION NO 3

For any substance,why does the temperature remain constant during the change of state?

ANSWER NO 3

During the change of state,the temperature remains constant. This is due to all the heat supplied to increase the to increase the temperature is utilised (as latent heat) in changing the state by overcoming the force of attraction between the particles. Therefore, this heat does not contribute in increasing the temperature of the substance.

QUESTION NO 4

Suggest a method to liquefy atmospheric gases.

ANSWER

Atmospheric gases can be liquefied by applying pressure and reducing temperature.

Saturday, 21 March 2020

NCERT SOLUTION CLASS 9 SCIENCE CHAPTER

NCERT SOLUTION SCIENCE CLASS 9 CHAPTER 1 ( MATTER IN OUR SURROUNDINGS)

PAGE -3

QUESTION No 1

Which of the following are matter?
Chair,air,love,smell,hate,almonds,thought,cold,cold drink,smell of perfume.

ANSWER

SOLID STATE: Chair and almond.
LIQUID STATE: Cold drink
GASEOUS STATE : Air and smell of perfume

QUESTION NO 2:

Give reason for the following observation:
The smell of hot sizzling food reaches you several meters away,but to get the smell from cold food you have to go close.

ANSWER:

Solids diffuses at a very slow rate. But if the temperature of a solid is increased then the particle of solids moves faster due to increased kinetic energy and thus diffusion of the solid particle increased in air. Hence .the smell of hot sizzling food reaches us even at a distance,but to get the smell from cold food you have to go close.

QUESTION NO 3

A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

ANSWER:

The ability of a diver to cut through water in a swimming pool show that matters is made up of particles.

QUESTION NO 4:

What are the characteristics of the particles of matter?

ANSWER:

The characteristics of particles of matter are -
1. Matter is made up of small particles.
2. Particles of matter have space between them.
3. Particles of matter are continuously moving.
4. Particles of matter attract each other.