Selina ICSE Solutions for Class 9 Chemistry – Matter and its Composition

Selina ICSE Solutions for Class 9 Chemistry – Matter and its Composition

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Selina ICSE Solutions for Class 9 Chemistry Chapter 1 Matter and its Composition

Exercise 1

Solution 1.

(a) Melting point: The constant temperature at which a solid changes into liquid state by absorbing heat energy is called melting point.

(b) Boiling point: It is the temperature at which a liquid changes into vapour under atmospheric pressure.

(c) Evaporation: The slow passing of molecules of a liquid into gaseous state at a temperature below its boiling point.

(d) Freezing: It is a process in which a liquid changes into solid state by giving out heat energy.

Solution 2.

Boiling point of a liquid can be raised by increasing the atmospheric pressure.

Solution 3.

On heating, solid wax melts into liquid wax, which on further heating, is converted into wax vapours. These changes can be seen in a burning candle. The candle is made up of a solid wax. When we light a candle, the wax near its wick melts. The molten wax rises up the wick and is converted into wax vapour. The wax vapour mixes with oxygen in the air and burns. In a lighted candle, you can see the solid and the liquid states of wax. The vapour of wax can be seen rising from the wick for some time after the candle is put out.
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Solution 4.

(a) Sublimation: The process by which a solid directly change to its vapour state (or gaseous state) without passing through liquid state and vice versa is called sublimation.

(b) Liquefaction: It is a process of change of state of a substance from gaseous state to liquid state at a particular temperature. It is also known as condensation.

(c) Melting: It is process of changing from solid state to a liquid state at a particular temperature.

(d) Boiling: The process by which a liquid rapidly changes into a gaseous state, by absorbing the heat energy is called boiling.

Solution 5.

(a)

An atomA molecule
Atom is a smallest particle of an element.Molecule is a group of two or more atoms combined together so it is bigger.
Atom consists of nucleus (containing protons and neutrons) and electrons.Molecule consists of combination of two or more like or different atoms chemically bound together e.g. H2, HCl, NaCl etc.
Atom can neither be seen through naked eye nor through magnifying microscope.Molecule is not visible to naked eye, while can be seen through highly magnifying microscope.
Atom cannot be further divided.Molecule can further be divided to give individual atoms.
Atoms may or may not have independent existence.Molecules are capable of having independent existence. For example, atom of oxygen (O) has no independent existence while its molecule exists as O2in nature.

(b)

BoilingEvaporation
Boiling is the process in which liquid gets converted into gaseous state.Evaporation is a process in which the liquid gets converted into its gaseous form at any temperature below its boiling point.
Boiling occurs at the entire mass of the liquid. That is, it is a bulk phenomenon.Evaporation occurs on the surface of the liquid. That is, it is a surface phenomenon.
Boiling occurs rapidly.Evaporation is a slow process.
Boiling occurs at a specific temperature.Evaporation occurs at any temperature.

(c)

MeltingBoiling
The process of changing from solid state to a liquid state at a particulartemperature is called melting or fusion.The process of change of liquid to vapour form all parts of the liquid at a particular temperature is called boiling.
Melting refers to the phenomenon when a solid transforms into a liquid.Boiling refers to the phenomenon when liquid transform into a gas.
Example: Melting of iceExample: Boiling of water

(d)

GasVapour
A substance exists as a gas at the room temperature and atmospheric pressure.A substance is a solid or liquid under ordinary condition but it is gaseousunder specific conditions.
It is present at ordinary conditions of temperature.Its temperature is lower than the boiling point of its liquid state.
e.g. – Nitrogen, oxygen.e.g. – Iodine, Camphor

Solution 6.

(a) Water boils of 100oC under 1 atmosphere pressure.
(b) At high altitude water boils below 100oC.
(c) A liquid evaporates below its boiling point.
(d) When a substance is heated kinetic energy of the particles increases.
(e) Solids have the negligible inter-particle space.
(f) Gases have the negligible inter-particle forces.

Solution 7.

(a) Increase in atmospheric pressure
(b) Sulphur
(c) Inter-conversion of state of matter

Solution 8.

(a) Sublimation
(b) Melting
(c) Evaporation
(d) Vaporisation

Solution 9.

(a) Increase in temperature favours Evaporation. When evaporation occurs, remaining liquid becomes cooler. The particles of the liquid absorb heat energy from surroundings to regain energy lost during evaporation which makes the surroundings cold.

(b) Earthen pot has pores which help in evaporation. Some of the water continuously seeps out from these pores. This water absorbs heat of vaporization from the remaining water and gets evaporate. Thus, the remaining water loses heat and gets cooled.

(c) This happens because, when the petrol changes from liquid state to the vapour state, is absorbs heat energy from the palm. The palm thus loses heat and gets cooled.

(d) In humid weather wet clothes take longer time to dry up due to the slow evaporation of water from their surface.

(e) Evaporation is a surface phenomenon. With increase in surface area, evaporation increases. Hot tea in Saucer cools faster than in a cup and hence we can sip faster.

Solution 10.

(a) Naphthalene balls become smaller day by day as they have very weak force of attraction operating between their particles, which break away from other particles from the surface of solid without heating.

(b) In gases the particles are far apart and there is enough space available for compression. Hence, gases can be compressed easily.

(c) Heat energy supplied increases the rate of vibration of the particles and decreases. The inter-particle attraction.

(d) Light has no mass and it does it occupy space. Thus, it is not considered as matter.

(e) According to ‘Law of Conservation of Mass’, “Mass can neither be created nor destroyed in a chemical reaction.” However, it may change from one form to other.

Solution 11.

In summers, we perspire more. Cotton being a good absorber of water helps in absorbing the sweat and exposes it to the atmosphere for evaporation. When sweat evaporates from our body, it takes heat from our body. The heat energy equal to the latent heat of vaporisation is absorbed from the body leaving the body cool.

Solution 12.

Balloon get heat from sun and on heating, the vibration of particles increases and the inter-particle force of attraction between them gets reduced, therefore, balloon bursts.

Solution 13.

Law of conservation of mass: It states that mass can neither be created nor destroyed in a chemical reaction. During any change, physical or chemical, matter is neither created nor destroyed. However it may change from one form to another.

Experimental Verification of Law of Conservation of Mass

Requirements: H-shaped tube called Landolt’s tube, Sodium chloride solution, silver nitrate solution, etc.

Procedure: A specially designed H-shaped tube is taken. Sodium chloride solution is taken in one limb ofthe tube and silver nitrate solution in the other limb as shown in figure. Both the limbs are now sealed and weighed. Now the tubes is averted so that the solutionscan mix up together and react chemically. The reaction takes place and a white precipitate of silver chloride is obtained.

Selina ICSE Solutions for Class 9 Chemistry - Matter and its Composition image - 2
The tube is weighed again. The mass of the tube is found to be exactly the same as the mass obtained before inverting the tube. Thus, this experiment clearly verifies the law of conservation of mass
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Solution 14.

Law of conservation of mass is applied to a burning candle. A candle is made of solid wax. When it is lighted, wax near its wick melts and changes into to liquid form. The molten wax rises up the wick and is converted into wax vapours. The wax vapours their mix with oxygen in the air.

Thus, in burning of candle the matter is neither created nor destroyed but one form is changed into the other form.

Solution 15.

The reaction is:
Selina ICSE Solutions for Class 9 Chemistry - Matter and its Composition image - 4
Total mass of reactants = (6 g + 5.3 g) = 11.3 g
Total mass of products = (8.2 + 2.2 + 0.9) g = 11.3 g
As the total mass of reactants is equal to the total mass of products. Hence, the reaction follows Law of conservation of mass.

Solution 16.

The reaction will be as follows:
Methane + Oxygen → Carbon dioxide + Water

According to law of conservation of mass,
Total mass of reactants = Total mass of products
Mass of methane + mass of oxygen = Mass of carbon dioxide + Mass of Water
Mass of methane  +  32 g  =  22  +  18 g
Mass of methane = (40 – 32) = 8 g
8g of methane is required.

Solution 17.

Word equation for the reaction is:
Sodium + Chlorine → Sodium Chloride

According to law of conservation of mass,
Total mass of reactants = Total mass of products
Mass of sodium + Mass of chlorine = Mass of sodium chloride
23 g+ Mass of chlorine = 58.5 g
Mass of chlorine = 58.5 – 23 = 35.5 g
35.5 g of chlorine is needed.

Solution 18.

Word equation for the reaction is:
Magnesium + Oxygen → Magnesium oxide

According to law of conservation of mass,
Total mass of reactants = Total mass of products
Mass of magnesium + Mass of oxide = Mass of magnesium oxide
4.8g           +          3.2g     = Mass of magnesium oxide
Mass of magnesium oxide = 8 g

Solution 19.

(a) (iv) No fixed shape and size highly compressible.
(b) (i) The solid starts melting.
(c) (i) evolved
(d) (iv) decreases with increasing pressure.
(e) (iii) Iodine

Solution 20.

(a) does not, melting, boiling
(b) liquid, solid
(c) temperature, temperature
(d) gaseous, sublimation
(e) high and negligible

Solution 21.

(a) freezing
(b) less
(c) sublimation
(d) remains constant

Solution 22.

Column AColumn B
(a) Constituent of matterMolecules
(b) No compressibilitySolid
(c) Maximum expansionGas
(d) Conversion of a gas into liquidCondensation

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New Simplified Chemistry Class 7 ICSE Solutions – Matter and Its Composition

New Simplified Chemistry Class 7 ICSE Solutions – Matter and Its Composition

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Points to Remember:

  1. Matter has mass and occupies space.
  2. Matter is made up of atoms and molecules.
  3. Atoms are the smallest particles of matter which may or may not have independent existence.
  4. 4. Molecules are capable of independent existence. They are
  5. made up of atoms of same kind or different kinds.
  6. The atoms and molecules are in random motion.
  7. There are gaps between the molecules of matter called as intermolecular space.
  8. There exists a force of attraction between the molecules
  9. known as intermolecular force of attraction.
  10. Matter exists in three states : solids, liquid and gas.
  11. Matter can change from one state to another on changing temperature and pressure.
  12. The change of state of a matter from one form into another I is called inter conversion of states of matter.

EXERCISE

Question 1.
Explain the meaning of the term matter with special reference to the term ‘substance’.
Answer:
Matter is the basic substance of which all materials, living or non-living are made of.

Question 2.
Name the three states of matter. On what basis are the three states classified.
Answer:
Three states of matter are:

  1. Solid
  2. Liquid
  3. Gases

Basis of the classification are:
Physical properties like:

  1. Mass
  2. Volume
  3. Shape
  4. Rigidity
  5. Density
  6. Arrangement of particles.

Question 3.
Each of the three states of matter has mass. Explain with the help simple experiments – that each state of matter has mass.
Answer:
Matter i.e. solids, liquids and Gases have mass explained by the following experiments.
(1) Solid
Experiment: A solid placed on one side of the scale, causes the scale to tilt towards one side.
Conclusion: The scale tilts due to the mass of the solid, hence all solids have mass.
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 1

(2) Liquid:         
Experiment: A liquid placed on one side of the scale, causes the scale to tilt towards one side.
Conclusion: The scale tilts due to the mass of the liquid, hence all liquids have mass.
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(3) Gas:
Experiment: An inflated balloon placed on one side of the scale causes it to tilt towards one side.
Conclusion: The scale tilts due to the mass of the gas, hence all gases have mass.
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 3

Question 4.
A measuring cylinder is filled with water to a particular mark. A piece of solid is immersed inside the measuring cylinder. State why the level of water in the measuring cylinder will rise up. If the solid is removed, what will be the new level of the water in the measuring cylinder. Give a reason for your answer.
Answer:
When a piece of solid stone is immersed inside the measuring cylinder. The water level rises up.
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 4
On removal of solid stone the water level in the measuring cylinder falls down back to the mark ‘A’.
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Hence, It show that the stone occupies the space of the water and thus pushes the water level up. This experiment or procedure also proves that all solids occupy space.

Question 5.
A glass beaker is half filled with water and an empty glass tumbler is inverted & lowered inside the glass beaker. State your observations on tilting the tumbler below the level of the water in the glass beaker. Give a reason for your answer.
Answer:
(1) Take a glass beaker half-filled with water as shown in diagram.
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 6
(2) Take an empty glass tumbler which contains air is inverted and lowered inside the glass beaker.
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 7
(3) On tilting the tumbler the air inside the tumbler is displaced and bubbles of air are seen coming out. The air is pushed out by the water on tilting the tumbler inside the beaker of water.This experiment or procedure also proves that air or gases occupy space
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Question 6.
Differentiate the general properties of solids, liquids and gases in the form of a table — with reference to
(a) mass (b) space  (c) volume (d) shape  (e) compressibility (f) density (g) free surfaces (h) diffusion.
Answer:
(a)
Solids— They have mass
Liquid — They have mass
Gases— They have mass

(b)
Solids— They Occupies space
Liquid— They Occupies space
Gases— They Occupies space

(c)
Solids-They have a definite volume
Liquid-They have a definite volume
Gases-They have no definite volume

(d)
Solids-They have a definite shape
Liquid-They have no shape
Gases-They have no shape

(e)
Solids-They have a no compressibility
Liquid-They have  slight compressibility
Gases-They have high compressibility

(f)
Solids-They have high density
Liquid-They have less density
Gases-They have least density

(g)
Solids-They have any number(of free surfaces)
Liquid-They have one free surfaces
Gases-They have no free surfaces

(f)
Solids-They have no diffusibility
Liquid-They have slight diffusibility
Gases-They have high proper diffusibility

Question 7.
State in which of the three states of matter- 
(a) Are the atoms or particles far apart
(b) The space between the particles is minimum.
(c) The force of attraction between the particles is very weak.
(d) The movement of the particles are neither about their own positions nor in any random direction.
Answer:
(a)
Gas  (b)  Solid  (c)  Gas  (d)  Gas

Question 8.
Give a reason why –
(a) Solids have a definite volume & a definite shape.
(b) Liquids have a definite volume but no definite shape.
(c) Gases have no definite volume and no definite shape.
Answer:
(a)
Any matter that is a solid has a definite shape and a definite volume. The molecules in a solid are in fixed positions and are dose together. Although the molecules can still vibrate, they cannot move from one part of the solid to another part. As a result, a solid does not easily change its shape or its volume.
(b)
Any matter that is a liquid has a definite volume but no definite shape. The molecules in a liquid are less closely packed and they have space between them as compared to solids. Although the molecules can easily move. The inter molecular forces of attraction between the particles are less strong as compared to solids. Hence liquid does have fixed shape and takes the shape of the container in which it is placed e. It has definite volume.
(c)
Any matter that is a gas has no definite volume and no definite shape. The molecules in a gas are least closely packed and inter molecular space between them is very large when compared to solids & liquids. The inter molecular force of attraction between the particles are negligible. As a result a liquid does not easily change its shape nor they have fixed volume.

Question 9.
Particles of matter possess energy due to their random motion. Compare the particles in a solid, -liquid & in a gas with reference to the amount of kinetic energy possessed by each.
Answer:
Particles of matter possess energy due to random motion is called kinetic energy.
Comparison of particles in a solid, liquid and gas with reference to kinetic energy are given in the following:
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 9

Question 10.
Describe simple experiments to show that –
(a) particles of matter have inter molecular attraction
(b) particles of matter are closely packed in solids and less in liquids.
Answer:
(a) Experiment – To show that particles off matter have inter molecular attraction
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Procedure:

  1. Globules of mercury are placed in a petri dish and kept at – a distance.
  2. The petri dish is shaken slowly and the mercury globules come together forming a big globule.
    Conclusion — The above experiment concludes that a force of attraction exist between particles of matter.

(b) Experiment – To show that particles are closely packed in solids and less in liquids

New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 11

Procedure:

  1. Take a measuring cylinder and add 100 ml. of water to it.
  2. Add crystals of sugar [solid] to the water and stir carefully to obtain a sugar solution.
  3. The volume of water after addition of sugar remains the
    same i.e. at the 100 ml. mark.

Conclusion

  1. Particles of a liquid [e.g. water] are less closely packed.
  2. Particles of a solid [e.g. sugar] are closely packed.
  3. The sugar particles fill the inter molecular spaces, which must be existing between the water molecules and hence the level of water in the measuring cylinder does not rise.

Question 11.
A crystal of iodine is placed in a closed flat bottom flask and heated. State how you would conclude from the observations seen, that inter particle space is minimum in solids and maximum in gases.
Answer:
Procedure:

  1. 40 A crystal of iodine is heated in a closed flask. The crystal containing ‘X’ no. of particles turns into vapours, which also contain ‘X’ no. of particles and fills the complete flask.

Conclusion

  1. Particles of a solid [e.g. crystal of iodine] are more closely packed.
  2. Particles of a gas [e.g. vapours of iodine] are least closely packed and fill the flask completely.

New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 12

Question 12.
Explain the term ‘inter conversion of matter’ – with ice as a starting material. State the term which refers to the conversion of a substance on heating from.
(a) solid state to liquid state
(b) liquid state to vapour state
(c) vapour state to liquid state
(d) liquid state to solid state.
Answer:
The phenomenon of change from one state to the other and then back to the original state without any change in its chemical composition is called ‘inter conversion of matter.’
The terms which refers to the conversion of a substance are:
(a) Melting
(b) Vaporisation
(c) Liquefaction
(d) Solidification

Question 13.
Give a reason why solids and liquids co-exist at their melting points.
Answer:
A substance exists in the solid state below its melting point and in the liquid state above its melting point. Hence, solids and liquids co-exist at their melting point.

Objective Type Questions
Matter and its composition

Question 1.
Match the characteristics of the three states of matter in List I with their correct answer from List II.
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 13

Answer:
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 14

Question 2.
Select the correct answer from the choice in bracket to complete each sentence:

  1. Matter is defined as anything that occupies space and has mass
  2. The three states of matter are classified on the basis of differences of certain physical.   
  3. Matter made up of one kind of particles is said to be homogeneous.
  4. Particles in a gas possess very large kinetic energy.
  5. The inter molecular force of attraction is maximum in solids.

Question 3.
Give reasons for the following.

  1. Gases have no definite shape or volume.
  2. Liquids have one free upper surface only.
  3. Globules of mercury kept in a petri dish, which is shaken slowly, come together forming a big globule.
  4. A crystal of iodine on slow heating in a closed flask, turns into vapours and fills the complete flask.
  5. An empty tumbler lowered into a glass beaker containing water, on tilting shows bubbles of air coming out, but when not tilted, no bubbles are seen.

Answer:

  1. Any matter that is a gas has no definite volume and no definite shape. The molecules in a gas are least closely packed and inter molecular space between them is very large when compared to solids & liquids. The inter molecular force of attraction between the particles are negligible. As a result a liquid does not easily change its shape nor they have fixed volume.
  2. Liquids have one free upper surface only because as liquids have a definite volume but no shape and while liquids are bounded by the container, they are placed in and have only one free surface, the upper surface.
  3. This is because the air is being pushed out by the water on tilting the tumbler inside the beaker of water. Air or gases occupy space.

Question 4.
State the correct term from A, B, C, D, E or F in List II which represents the – change of state of matter or its relevant property from List I
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Answer:
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 16

Question 5.
Match the arrangement of atoms in the three states of matter in List I with the correct state in List II.
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Answer:
New Simplified Chemistry Class 7 ICSE Solutions - Matter and Its Composition 18