# Matter in Our Surroundings Class 9 Science Exam Questions

Please refer to Matter In Our Surroundings Class 9 Science Exam Questions provided below. These questions and answers for Class 9 Science have been designed based on the past trend of questions and important topics in your class 9 Science books. You should go through all Class 9 Science Important Questions provided by our teachers which will help you to get more marks in upcoming exams.

## Class 9 Science Exam Questions Matter In Our Surroundings

Class 9 Science students should read and understand the important questions and answers provided below for Matter In Our Surroundings which will help them to understand all important and difficult topics.

#### 1 Mark Questions

Question. If the humidity in the air increase then the rate of evaporation:
(a) decrease
(b) increase
(c) remain same
(d) both (b) and (a) depending upon the temperature

A

Question. Which of the following statement is correct?
(a) boiling is a bulk phenomenon and evaporation is a surface phenomenon
(b) boiling is a surface phenomenon and evaporation is a bulk phenomenon
(c) boiling and evaporation both are surface phenomenon
(d) boiling and surface both are bulk phenomenon

A

Question. If the temperature of a place is increase then evaporation:
(a) decrease
(b) increase
(c) remain same
(d) none of the above

B

Question. Which of the following have least inter atomic spacing?
(a) solid
(b) liquid
(c) gases
(d) plasma

A

Question. If you decrease the surface area and increase the temperature, then the rate of evaporation
(a) increase
(b) decrease
(c) remain same
(d) may increase or decrease depending upon other factors

C

Question. 300k will have its corresponding temperature in degree centigrade as:
(a) 30°C
(b) 300°C
(c) 27°C
(d) 673°C

C

Question. Liquid to gas and gas to liquid changes are called:
(a) vaporization and condensation
(b) condensation and vaporization
(c) sublimation and condensation
(d) condensation and sublimation

A

Question. Physical state of water at 25°C 0° and 100°C is respectively
(a) liquid, solid and gas
(b) solid, liquid and gas
(c) solid, gas and liquid
(d) gas, solid and liquid

A

Question. State two factors on which change of state of matter depends ?
Answer. The change of state of matter mainly depends upon two factors.
(i) Temperature
(ii) Pressure

Question. Convert the following temperatures to the Kelvin scale.
(a) 25° C
(b) 373° C.
Answer. K = °C + 273 = 373 + 273 = 656 K

Question. Why do we say that evaporation is a surface phenomenon?
Answer. Evaporation is called a surface phenomenon because only particles of the surface of liquid gains energy and changes into vapours.

Question. Suggest a method to liquefy atmospheric gases.
Answer. If we decrease temperature and increasing pressure we can liquefy the atmospheric gases.

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

Question. What is the physical state of water at—
(a) 25oC (b) 0oC (c) 100oC ?
Answer. At 25°C water is liquid, at 0oC water is solid(ice), at 100oC water is gas(water vapour).

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

Question. What is the physical state of water at:
a. 250oC
b. 100oC
Answer. b. 100oC is the boiling point of water hence at both the temperatures water is in gaseous state i.e. water vapour.

Question. Can kelvin scale have negative temperatures ?
Answer. No. because on the kelvin scale the lowest theoretical temperature which can be obtained i.e (– 273 ° C) is taken as OK.

Question. Is dry ice the same thing as ordinary ice ?
Answer. No, dry ice is not same as ordinary ice. Dry ice is a solid Carbon dioxide, while ordinary ice is a freezed water.

Question. What is sublimation ?
Answer. Sublimation is a process in which a such substance, which go under sublimation are known as sublime for eg : Camphor, naphthalene balls,

Question. Camphor disappears with out leaving any residue. Explain ?
Answer. Camphor disappears without leaving any residue because of sublimation as it changes its state directly form solid to gas without changing to liquid.

Question. Why do we feel cool when we touch a piece of ice ?
Answer. We feel cool because the temperature of ice is 0°C and our body’s temperature is higher than 0°C.

Question. Which property is shown by ammonium chloride but not by sodium chloride ?
Answer. Sublimation is the property that is shown by ammonium chloride but not by sodium chloride.

Question. Which process causes dry ice to change into carbon dioxide ?
Answer. Sublimation causes dry ice to change into carbon dioxide.

Question. Explain the cooling effect of evaporation while sweating ?
Answer. When we sweat, water in it evaporates taking latent heat from our body. This cause cooling.

Question. In which unit pressure is measured ?

Question. Is it possible to store solid carbon dioxide at low pressure ?
Answer. No, its not possible to store solid carbon dioxide at low pressure because at low pressure it turns into vapour

Question. Why we should not wear warm clothes in summer?
Or
Why it is recommended to wear cotton clothes in summer ?
Answer. Cotton absorbs water and thus sweats very fast so sweat comes outside clothes in contact with atmosphere. Then it evaporates and gives cooling

Question. Define the process condensation and freezing ?
Answer. Condensation : It is a process in which a gas changes into a liquid on cooling Freezing : It is a process in which a liquid changes into a solid on cooling

Question. When, we use saucer to drink tea, its cools down faster as
compared to cup ? why ?
Answer. When teas is put in saucer evaporation is faster due to more surface area. This cools tea faster and makes it easier to drink.

#### 2 Mark Questions

Question. Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer. While melting ice absorbs latent heat of melting from the surroundings and gets changed into water that makes the cooling effect more intense as compared to water at same temperature.

Question. What produces more severe burns, boiling water or steam?
Answer. As compared to boiling water it is observed that steam produces more severe burns since as the steam changes into boiling water it releases heat of condensation which is equivalent to latent heat of water result is more severe burning.

Question. When heat is being supplied to a solid, then what does the heat energy do to the particles of solid?
Answer. The heat supplied to the solid, helps the particles to overcome the forces of attraction between them and increases their kinetic energy, as a result of which particle break free the forces of attraction and changes to liquid state.

Question. What happen when we apply pressure to the particles of matter?
Answer. When we apply pressure to the particles of the matter, then the particles come closer to each other because pressure is the force applied per cross-sectional area so the force applied brings the particle closer to each other.

Question. What happens when the temperature of the solids increase?
Answer. When temperature of the solid is increased, kinetic energy of the particles increases as results particles vibrates more freely with greater speed. They overcome the force of attraction between the particles and start moving more freely.

Question. Why is it that on increasing the wind speed the rate of evaporation increases?
Answer. When the speed of wind increases, then they blow away with them the water vapour in the air and as results evaporation will increase because the surrounding air will be able to receive more vapours and hence evaporation increases.

Question. How does evaporation cause cooling?
Answer. When a substance evaporates from a surface, it absorbs heat from the surface and change into vapour state. So, the particle of liquid absorbs energy from the surface and the absorption of heat from makes the surface cool.

Question. Why is it that a wooden chair should be called a solid and not a liquid?
Answer. A wooden chair should be called a solid not a liquid because the particles of wooden chair are very close to each other, it has negligible compressibility and it maintains its shape when subjective to outside force.

Question. Define melting point and Boiling point ?
Answer. Melting point : It is the temperature at which a solid changes to liquid. Different Higher melting point means large force of attraction between particles.
Boiling point : It is the temperature at which a liquid changes to gas.

Question. Why is oxygen called as gas ? Give two reasons ?
Answer. (i) Oxygen neither has a fixed shape nor a fixed volume.
(ii) Oxygen exerts pressure due to the collisions of the molecules on the walls of the containing vessel.

Question. Write down the factors affecting Evaporation ?
(i) Temperature
(ii) Surface area
(iii) Humidity
(iv) Wind

Question. Write down three application of compressed gas ?
Answer. (i) Compressed helium gas is filled in air balloons
(ii) Compressed natural gas (CNG) is filled in cylinders which are used in vehicles.
(iii) Liquefied petroleum gas (LPG) is filled in cylinders which are used for cooking.

Question. The kelvin scale temperature is 0K. What is the corresponding Celsius scale temperature ?
Answer. °C = K – 273 → Conversion formula
°C = O – 273
temperature in °C = – 273°C

Question. The latent heat of fusion of ice is 3.34 × 105 j / Kg, what does this means ?
Answer. The latent heat of fusion of ice is 3.34 × 105 j / kg means that 3.34 × 105 j /kg . Heat is required to change 1 kg of ice into water at its melting point at the same temperature

Question. Why solid carbon dioxide is known as dry ice ? What happen when we heat it ?
Answer. Solid carbon dioxide is known as dry ice because it looks like ice and does not met on heating. When we heat solid carbon dioxide, it directly gets converted to vapour without passing through the liquid state.

Question. What is matter ?
Answer. Anything which occupies space and has mass is called matter. In other words, anything which has mass and volume is called matter.
For example : chair, table, computer, mouse etc.

Question.  Identify the matter from the given terms :
Answer. Chair, Air, Love, Hate, Almonds, Thought, Cold, Cold drinks.
Chair, Air, Almonds, Cold drinks are different forms of matter

Question. Name the two gases which are supplied in compressed form ?
Answer. The two gases which are supplied in compressed form are.
(i) LPG (Liquefied petroleum gas ) in homes
(ii) Oxygen in hospitals

Question. Give reasons for the following observation:
The smell of hot sizzling food reaches you several meters way, but to get the smell from cold food you have to go close.
Since hot sizzling food has temperature higher than cold food and at higher temperature diffusion rate (movement) of particles is very fast due to this the smell of hot sizzling reaches us from several meters away.

Question. The mass per unit volume of 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.
Arranging substances in their increasing order of densities:
Air< exhaust from chimneys< cotton< water< honey< chalk< iron.

Question. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Ice represents solid state of water. If we observe its 3D structure, a large empty space is found inside ice as a result it becomes less in weight as compared to water. Due to its specific structure though solid, ice floats on water.

Question. Why does a desert cooler cool better on a hot dry day?
On a hot dry day rate of evaporation is faster. In a desert cooler when exhaust fan is on, hot air enters through the straw mates and at this site evaporation of water takes place and that also at faster rate. It takes away heat from air so the air becomes cool even cooler on a hot dry day.

Question. How does the water kept in an earthen pot (matka) become cool during summer?
During summers the water present on the surface of the earthen pot evaporates which causes the cooling effect. Besides earthen pot bears pores on it hence evaporation occurs continuously so is cooling.

Question. Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Some liquids get quickly vapourised and they are called volatile liquids. Acetone, petrol and perfume are also volatile liquids therefore they get heat from our palm and cause cooling.

Question. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Saucer has a bigger surface area as compared to cup. Since evaporation is a surface phenomenon, by using a saucer instead of cup we are increasing the surface are for evaporation to occur. Faster evaporation of particles of tea or milk allows cooling and taking a sip becomes easier.

Question. What type of clothes should we wear in summer?
Cotton is a good absorbant of water hence it absorbs sweat quite well and pores in the fabric expose that sweat to easy evaporation hence we should prefer wearing cotton clothes in summer.

Question. Convert the following temperatures to the celsius scale.
(a) 293 K (b) 470 K.
a) oC = K – 273 = 293 – 273 = 20oC
b) °C = K – 273 = 470 – 273 = 197°C

#### 3 Mark Questions

Question. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Answer. If diver has ability to cut through water in a swimming pool then it shows that the particles of matter have a kind of force working between them. Because of this force the particles of matter remain together till some external force is applied.

Question. What are the characteristics of the particles of matter?
Answer. The characteristics of particles of matter are as follows:
i) particles of matter have gap between them.
ii) particles of matter are in continuous motion
iii) particles of matter have an attraction force between them to keep them together.

Question. Are the three state of matter inter-convertible? How can they interconnect?

Answer. Yes, three states of matter are inter-convertible.
(a) Solid can be changed into liquid by boiling and liquid can be changed to solid by cooling it i.e. by solidification.
(b) Liquid can be changed to gas by vaporization by heating it and gas can be changed to liquid by condensation i.e. subjecting it to low temperature.
(c) Solid can be changed to gaseous form/state by sublimation and liquid can be changed to solid by condensation.

Question. Why should we wear cotton clothes in summer?
Answer. During summer, we perspire more and the particles at the surface of the liquid gain energy from the surrounding or body surface and change into vapour. Now, cotton being an absorber of water helps in absorbing the sweat and exposed it to atmosphere for easy evaporation and we feel cool.

Question. Differentiate between physical and chemical change?

Question. What is the state of inter particle distance inside a solid, liquid and gas?
Answer. In solids, the particles are very close to each other and are bonded by strong forces of attraction so inter particle distance is least. In liquid, the particles are far away from each other and are bonded by weak forces of attraction, so inter particle distance is large. In gases, particles are very far apart from each other and are bonded by very weak forces of attraction so, inter particle distance is a largest.

Question. Why it is that to smell cold food, we have to go close but smell of hot food reaches us several meters away?
Answer. In hot food, the particles are at high temperature so quickly changes to vapour and hence the vapours have greater kinetic energy so travel faster and travel to far off distances. Whereas in cold food, because of temperature being low, particles do not change to vapour state and hence cannot travel faster so the smell does not reaches to a person sitting far away.

Question. What is distillation and fractional distillation? What is the basic property that separates the two methods?
Answer. Distillation is used for the separation of components of a mixture containing two miscible liquid that boil without decomposition and have sufficient difference in their boiling points. Fractional distillation is used for the separation of components of a mixture containing more than two miscible liquids for which the difference in their boiling points is less than 25k. The property that separates the two processes is difference in the boiling points of the components of the mixture i.e. if difference in boiling points is large then we use distillation but if difference in boiling points is less, we use fractional distillation.

Question. Define solid, liquid and gas with example ?
Answer. Solid : Solids have fireed volume and shape in solids. In solids, particles are closely packed and they have very less spacing between them
Examples : stone, wood, brick etc .
Liquid : Liquids have fixed volume but indefinite shape. In liquids there is a weaker force of attraction and more spacing between the particles
Examples : milk, water, petrol etc.
Gas : Gases have indefinite shape and volume particles of gases have very large spacing and very weak attraction between them
Examples : air, oxygen, hydrogen etc

Question. Out of solids, liquids and gases, which one has .
Answer. (a) Maximum movement of particles
(b) Maximum inter particle forces of attraction .
(c) Minimum spaces in between constituent particles.
(a) Because of large spaces between the particles of a gas, gases have maximum movement of particles.
(b) and (c) In Solids, the spaces between the constituent particles are the minimum and hence the forces of attraction are the strongest.

Question. How will you justify that ice, water and steam are the three states of a substance and not different substances ?
When ice is melted, water is produced and when water is heated steam
is produced on the other hand, when water is cooled further, ice is produced.
Therefore ice, water and steam are the three states of a substance.

Question. What are the properties of gases ?
Answer. (i) Gases can be compressed easily
(ii) Gases neither have fixed shape nor fixed volume
(iii) Gases have very low densities
(iv) Gases have fluidity
(v) Particles of gases have very large spacing and very weak attraction between them.

Question. What is meant by physical property of substance ? Name the important physical property ?
Answer. Physical properties : Those properties of a substance which we can observed without altering the identity of the state.
Colour
Smell
Density
Solubicity
Melting point and boiling point
Conductivity

Question. Write down different units used to measure temperature ? Write down the relation between them ?
Answer. Different units can be used to measure the temperature in different scales. Most known units of measurement are kelvin and Degree Celsius.
(i) Kelvin is the SI unit of temperature . The symbol of kelvin is K
(ii) Degree Celsius is written as °’C’ and it is a common unit of temperature. Relation between temperature in °K & Temperature in Celsius.
Temperature in K = Temperature in ° C + 273

Question. Define latent heat of Fusion, is it same as latent heat of vaporization ? Comment ?
Answer. Latent heat of fusion is the amount of heat required to convert 1 kg of solid at its melting point to liquid at same temperature.
Latent heat of vaporization It is the amount of heat required to convert 1 kg of liquid at its boiling point to gas at same temperature. Different liquid has different latent heat of vaporization.
No, Latent heat of fusion is not same as latent heat of vaporization.

Question. Convert the following
(a) 573 K
(b) 36°C
(c) 373°C

Answer. (a) 573 – 273 = 300°C
(b) 36 + 273 = 309°K
(c) 373 + 273 = 646 K

Question. List the important properties of matter ?
Matter is made up of small particles
These particles are very small in size
These particles are moving constantly
These particles have spaces between them
Particles of matter attract each other because of force of attraction.

Question. Define latent heat of vaporization and latent heat of fusion.
Answer. Latent heat of vaporization is the heat energy required to change 1 kg of a liquid to gas at atmospheric pressure without changing its state. Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid without changing its state.

Question. If the melting point of an object A is high then what state you expect it to be at room temperature?
Answer. Melting point is the temperature at which a solid melts/change into a liquid state. So, if the melting point of an object A is higher means that it requires greater temperature to change into liquid the object will remain the same at room temperature because room temperature is less and the object cannot change its state.

Question. Convert the following temperature to Celsius scale:
i) 300 K
ii) 573 K
ii) K = 273 + oC
oC = K – 273 = 300 – 273 = 27oC
iii) oC = 573 – 273 = 300oC

Question. Give reason for the following observations.
(a) Naphthalene balls disappear with time without leaving anysolid.
(b) We can get the smell of perfume sitting several metres away.
Answer. a) Some substances possess the property of sublimation like camphor and naphthalene balls. Such substances directly change from solid to gaseous state without changing into liquid like ice→water→water vapour does. Therefore, naphthalene balls disappear with time without leaving any solid.
b) Being a volatile substance (gets evaporated easily) perfumes change from liquid to gaseous state very fast. Those particles mix up with air particles and diffuse to reach our nostrils such that we get the smell of perfume sitting several metres away.

Question. Give two reasons to justify—
(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.
Answer. a) The room temperature is generally always more than 0°C and less than and 100°C within this range water is a) liquid so water at room temperature is a liquid.
b) The melting point of iron is much higher than the room temperature therefore an iron almirah is a solid at room temperature.

Question. What is evaporation? What are the factors affecting it?
Answer. Evaporation is the process by which water (liquid) changes to vapours at any temperature below its boiling point.
Factor on which evaporation depends:
(a) Surface area
(b) Humidity
(c) Wind speed
(d) Temperature

#### 5 Mark Questions

Question. (a) Tabulate the differences in the characteristics of states of matter.
(b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

(b) Rigidity→ It is the property of matter to maintain its shape even if external forces work and the solids show this property.
Compressibility → It is the property of matter to allow compression under high pressure and the gases show this property.
Fluidity → It is the property of a substance to easily flow and allow change in its shape under external forces and this property is exhibited by both liquids and gases.
Filling a gas container → Gases can be compressed easily hence they can be filled within a vessel at high pressure. This property of gases allows their convenient filling into a small container or cylinder and that also in a large volume. It also allows their easy transport from one place to the other eg CNG.
Shape→ According to the type of matter shape differs depending upon location of particles like Solids have definite shape while Liquids acquire the shape of their container and gases as such don’t have any shape.
Kinetic energy → It is the kind of energy present in an object when it is under motion as the particles of that object/matter are continuously moving therefore matter has kinetic energy. However greater is the movement more will be the kinetic energy and vice a versa i.e. solid < liquid < gas Density → Mass per unit volume of a substance/matter is known as its density i.e.
density = mass/volume.

Question. 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) Since the attraction force between particles of a gas is negligible i.e. extremely less hence particles freely move/flow in all possible directions as a result gas fills completely the vessel in which it is kept.
(b) Freely moving particles of gas hit the walls of its container continuously and randomly therefore such random and erratic motion of gas particles exerts pressure on the walls of the container.
(c) A wooden table particles are quite rigid, have a fixed location and also possess a definite shape and volume. Due to all these properties we should call a wooden table a solid substance.
(d) Air is a mixture of gases and since particles of gas are far apart so same is true for air therefore we can easily move our hand in air. But a solid block of wood is hard and rigid that resists any change in location of its particles hence we need a karate expert in case of a solid block of wood.

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

Answer. A – Fusion (Heating – Melting)
B – Vapourisation
C – Cooling – Condensation (Liquefaction)
D – Cooling – Freezing (Solidification)
E – Sublimation
F – Solidification

Question. A solution of H2 SO4 is labeled 40%. The density of the solution is 1.3gm/l. what is the concentration of the solution in % (m/v)?
Answer. Concentration of the solution is 40%
This means that
100 gm of the solution contains 40g of H2 So4

Question. Give an experiment to show that ammonium chloride undergoes sublimation.
Answer. Experiment to show that ammonium chloride (NH4CI) undergoes sublimation:
(a) Take an inverted funnel and inside it china dish with crystal of ammonium chloride. (NH4CI)
(b) Heat the crystals with the help of a burner.
(c) As soon as the crystal is heated, we observe the vapours of and the solidified Ammonium chloride (NH4CI) along the walls at the upper end of the beaker.
(d) This shows that solid ammonium chloride does not undergo liquid state but directly changes to vapour state which them solidifies i.e. it undergoes sublimation (solid changes directly to gases without undergoing liquid state).

Question. Compare the properties of solids, liquids and gases ?

Question. Comment upon the following : Rigidity, Compressibility, fluidity, Density, shape and volume
Answer. Compressibility : It means tendency to decrease volume when some outside force is applied. Spacing between particles of gases can be decreased so gases have high compressibility. But spacing between particles of solid or liquid can not be decreased, so they cannot be compressed.
Applications of compressed Gas –
– Compressed helium gas is filled in air balloons.
– Compressed natural gas (CNG) is filled in cylinders which are used for cooking.
Rigidity – It is the property of a substance to resist any deformation like change in shape, being compressed etc. Solids have high rigidity, liquids have less rigidity and gases have no rigidity.
Fluidity
– Fluids are substances which can flow
– Liquids and gases have fluidity
– But solids do not have fluidity
Density : It means mass per unit volume
Density = Mass / Volume
Particles in solids are very closely packed So they have high density. In gases, there is plaenty of space between particles due to which density is low.
Shape and volume
Shape – Due to less attraction force between particles, particles of liquid and gas can easily move around. This they can take any shape as per the container.
Volume –
– gases have so little attraction among particles that they can easily change spacing between them selves, So they can easily change their volume.
– In liquids, attraction force is large enough So that spacing between particles does not change easily, So liquid has fireed volume and same with solids.
– Solids can change shape on applying force Liquids and gases do not need force to be applied for changing shape.
– Some solids have gas inside them, So they can be easily squeezed to change shope.

Question. Give two reasons to justify –
Answer. (a) Water at room temperature is a liquid
(b) An Iron almirah is a solid at room temperature.
(a) Water is a liquid because of the following two reasons :
(i) liquids do not have a fixed shape : They take the shape of the container in which they are kept
(ii) Liquids have a fixed volume : Take 100 ml of water in a beaker. Transfer it to a glass, It still remains same, therefore, water is a liquid.
(b) An Iron almirah is a solid at room temperature due to following reasons :
(i) Iron almirah has a fixed shape and a fixed volume
(ii) If we apply force in limits, the volume of iron almirah cannot changed, hence it is incompressible, So it is a solid.

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