NCERT Solutions For Class 9 Science Chapter 1 Matter In Our Surroundings
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NCERT Solutions For Class 9 Science Chapter 1 Matter In Our Surroundings 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 Matter in our Surroundings 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 Matter in Our Surroundings below and prepare for your tests easily.
NCERT Solution for Class 9
Science – Chapter 1 Matter In Our Surroundings
Q. 1. Convert the following temperatures to the celsius scale .
( a ) 293 K
( b ) 470 K.
Ans . ( a ) 293 K = ( 293-273 ) ° C = 20 ° C
( b ) 470 K = ( 470-273 ) ° C = 197 ° C
Q. 2. Convert the following temperatures into the Kelvin scale .
( a ) 25 ° C
( b ) 373 ° C
Ans . ( a ) 25 ° C = 25 + 273 = 298 K
( b ) 373 ° C = 373 + 273 = 646 K
Q. 3. Give reasons for the following observations :
( a ) Naphthalene balls disappear with time without leaving any solid .
( b ) We can get the smell of perfume sitting several meters away .
Ans . ( a ) Naphthalene shows the property of sublimation . In sublimation , solid evaporates into gas directly without changing into liquid . Evaporation of naphthalene takes place easily and thus it disappears with time without leaving a solid .
( b ) Gaseous particles are free to move in any direction and diffuse very fast in air . Perfumes are in liquid form but it vaporises very fast and its vapours diffuse into air easily . That is why we can smell perfume sitting several meters away .
Q. 4. Arrange the following in increasing order of forces of attraction between the particles : water , sugar , oxygen .
Ans . The particles of matter have forces of attraction in between which keeps them together with different strength . More is the space between the particles of matter , less is the force of attraction . Thus , the increasing order will be :
Oxygen < Water < Sugar .
Q. 5 . Give two reasons to justify :
( a ) Water at room temperature is a liquid .
( b ) An iron almirah is a solid at room temperature .
Ans . ( a ) Water at room temperature is a liquid because :
1. Normally , room temperature is between 20-25 ° C , and at this temperature water has fluidity .
2. At room temperature when water has fluidity , it has definite volume but no definite shape .
( b ) An iron almirah is a solid at room temperature because it is rigid and has a definite shape .
Q. 6. Why is ice at 273 K more effective in cooling than water at the same temperature ?
Ans . Hence lesser energy will be taken from the surroundings . So , at same temperature of 273K , large amount of heat will be removed by ice from the surroundings than in case of water . Hence , ice at 273 K is more effective in cooling than water at the same temperature .
Q. 7. What produces more severe burns , boiling water or steam ?
Ans . Steam produces more severe burns than boiling water because steam has more energy than boiling water , due to its latent heat of vaporization .
Q. 8. Name A , B , C , D , E and F in the following diagram showing change in its state :
Ans . A → Melting : Solid is changing into liquid as heat is increasing and pressure is decreasing , for example , ice melts into water .
B → Boiling : Liquid is changing into gas as temperature is increasing and pressure is decreasing , for example , water changes into vapours .
C → Condensation : When water is collected as droplets on a cold surface when humid air is in contact with it or the conversion of a vapour or gas to a liquid . In this state , temperature is decreasing and pressure is increasing , which results in condensation .
D → Solidification : When liquid changes into solid , for example , water changes into ice .
E → Sublimation : The change from solid to gas without passing through the liquid phase ; In this state with the increase in heat and decrease in pressure results in change of solid to gas without changing into liquid , for example , camphor .
F → De – sublimation : The reverse process of sublimation is deposition or de – sublimation ; in this state , a substance passes directly from a gas to a solid phase .
Q. 9. What produces more severe burns , boiling water or steam ? [ KVS , Patna Region , SA – I , 2015-16 ]
Ans . Steam produces more severe burns than boiling water because steam has more energy than boiling water , due to its latent heat of vaporization .
Q. 1. Which of the following are matter
Chair , air , love , smell , hate , almonds , thought , cold , cold drink , smell of perfume . [ NCERT Q. 1 , Page 3 ]
Ans . ( i ) Matter is anything that occupies space and has mass . It can be present in three physical states – ( a ) solid , ( b ) liquid and ( c ) gaseous .
In the given list , the following are matters :
( ii ) Chair and almond are the solid states of matter .
( iii ) Cold drink is liquid state of matter .
( iv ) Air and smell of perfume are gaseous states of matter .
The smell of any substance ( say , perfume ) is the gaseous form of that substance which our olfactory system can detect ( even at very low concentrations ) . Hence , smell of perfume is matter . But love , hate , smell , thought and cold are senses and emotions which are not the matter .
Q. 2. Give reason : The smell of hot sizzling food reaches you several metres away , but to get the smell from cold food you have to go close . [ NCERT Q. 2 , Page 3 ]
Ans . The kinetic energy of solid particles is very low . But , as the temperature of the solid increases , the kinetic energy also increases and they start moving freely . Thus , the rate of diffusion of the solid particles into air increases . Therefore , the smell of hot sizzling food reaches us even at a distance , but to get the smell from cold food we have to go close .
Q. 3. A diver is able to cut through water in a swimming pool . Which property of matter does this observation show ? [ NCERT Q. 3 , Page 3 ]
Ans . The ability of a diver to cut through water in a swimming pool shows that liquid state of matter is made up of particles . [ 2 ]
Q. 4. What are the characteristics of particles of matter ? [ NCERT Q. 4 , Page 3 ]
Ans . The characteristics of particles of matter are as following :
( i ) Particles of matter have spaces in between them .
( ii ) They are continuously moving .
( iii ) They attract each other .
Q. 5 . 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 chimney , honey , water , chalk , cotton and iron . [ NCERT Q. 1 , Page 6 ]
Ans . The given substances in the increasing order of their densities can be represented as follows :
Air < Exhaust from chimney < Cotton < Water < Honey < Chalk < Iron
Q. 6. ( 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 . [ NCERT Q. 2 , Page 6 ]
Ans . ( a ) The differences in the characteristics of states of matter are as below :
( b ) Comment :
1. Rigidity is the property of matter to resist the change of its shape .
2. Compressibility is the capability of a substance to be reduced to a lower volume when force is applied .
3. Fluidity is the ability to flow .
4. Filling a gas container means gas attains the shape of the container .
5. Shape describes a fixed boundary .
6. Kinetic energy is the energy influenced by a particle due to its motion .
7. Density is mass per unit volume .
Q. 7. 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 . [ NCERT Q. 3 , Page 6 ]
Ans . ( a ) There is very less attraction between particles of gas . Thus , gas particles move freely in all directions . So , 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 hit each other and also hit the walls of the container with a force . Thus , gas exerts pressure on the walls of the container .
( c ) A wooden table has a definite shape and volume . It is very stiff and cannot be compressed , that is , it has the characteristics of a solid . Hence , a wooden table should be called as a solid .
( d ) Particles of air have large spaces between them . Whereas , wood has little space between its particles . Also , it is rigid . Thus , we can easily move our hands in air , but to do the same through a solid block of wood , we need a karate expert . [ 3 ]
Q. 8. Liquids generally have lower density as compared to solids . But you must have observed that ice floats on water . Find out why . [ NCERT Q. 4 , Page 6 ]
Ans . Liquids generally have lower density as compared to solids . But ice floats on water . This is because :
( i ) Density is mass per unit volume of a substance . As the volume of a substance increases , its density decreases .
( ii ) Ice has large number of vacant spaces between its particles which is larger as compared to the spaces present between the particles of water . Therefore , the volume of ice is greater than that of water .
( iii ) As the volume of ice is greater than that of water . The density of ice is less than that of water . A substance with lower density than water can float on water . Therefore , ice floats on water .
Q.9 . Convert the following temperature to Celsius scale :
( a ) 300 K
( b ) 573 K [ NCERT Q. 1 , Page 9 ]
Ans . ( a ) 300 K = ( 300-273 )° C = 27° C
( b ) 573 K = ( 573-273 )° C = 300° C
Q. 10. What is the physical state of water at :
( a ) 250 ° C
( b ) 100 ° C [ NCERT Q. 2 , Page 9 ]
Ans . ( a ) As the boiling point of water is 100 ° C , so above this , i.e. , at 250 ° C water exists in gaseous state .
( b ) At 100 ° C , water can exist in both liquid and gaseous forms . Because , at this temperature , after getting the heat equal to the latent heat of vaporization , water starts changing from liquid state to gaseous state .
Q. 11. For any substance , why does the temperature remain constant during the change of state ? [ NCERT Q. 3 , Page 9 ]
Ans . Temperature remains constant during the change of state because :
( i ) The heat provided to increase the temperature is used as latent heat .
( ii ) The heat provided overcome the forces of attraction between the particles in changing the state .
( iii ) The heat energy supplied is used up in changing the state of matter . Thus The heat does not help in increasing the temperature of the substance .
Q. 12. Suggest a method to liquefy atmospheric gases . [ NCERT Q. 4 , Page 9 ]
Ans . Atmospheric gases can be liquefied by applying pressure and by reducing the temperature . day ?
Q. 13. Why does a desert cooler cool better on a hot dry ? [ NCERT Q. 1 , Page 10 ]
Ans . A desert cooler cools better on a hot dry day because :
( i ) When a liquid evaporates , the particles of the liquid absorb energy from the surroundings to compensate the loss of energy during evaporation . This makes the surroundings cool .
( ii ) In a desert room cooler , the cooling is due to the process of evaporation . The water inside the cooler is made to evaporate which leads to absorption of energy from surroundings and thus cool the surroundings .
( iii ) Evaporation depends on the amount of water vapour present in air . If the humidity present in air is less , then evaporation is more , because the temperature of the atmosphere increases the rate of evaporation also . This gives better cooling effect .
( iv ) On a hot dry day temperature is high and humidity is less which helps in better evaporation . Due to the higher rate of evaporation , it gives better cooling effect .
( v ) Also , in a desert cooler , the three sides have aerated grass pads and a fan on the front side . Water is circulated along the three sides of the cooler . The hot air that enters into the cooler evaporates the water inside it and becomes cool . Then , cool air is pushed out which cools the room .
Q. 14. How does water kept in an earthen pot ( matka ) become cool during summers ? [ NCERT Q. 2 , Page 10 ]
Ans . During summer , water kept in an earthen pot becomes cool because of :
( i ) Evaporation : When a liquid changes to a gaseous ( or vapour ) state without boiling , it is known as evaporation .
( ii ) The earthen pot is made of mud and has many minute pores . Through these pores the water placed inside the earthen pot evaporates .
( iii ) To evaporate , the water needs to absorb heat , this is done by absorbing heat from the liquid within the earthen pot and the earthen pot itself . Due to this process of continuous absorption of heat from the water inside the matka , in a few hours , this water becomes cool .
Q. 15. Why does our palm feel cold when we put some acetone or petrol or perfume on it ? [ NCERT Q. 3 , Page 10 ]
Ans . Our palm feel cold when we put some acetone or petrol or perfume on it , because :
( i ) Acetone is a volatile substance .
( ii ) When we put some acetone or petrol or perfume on our palm , it evaporates and we feel cold .
( iii ) The latent heat of vaporisation , the liquid molecules absorb energy from surrounding or the surface of the palm to compensate for the loss of energy , making the surroundings cool , thus our palm feels cold .
( iv ) Acetone , petrol and perfume have very low boiling temperature .
( v ) When we put some acetone on our palm the particles of it gain energy from our palm and evaporate quickly which causes cooling .
Q. 16. Why are we able to sip hot tea or milk faster from a saucer than a cup ? [ NCERT Q. 4 , Page 10 ]
Ans . Hot liquid can evaporate faster and cools faster in large surface area . A saucer has larger surface area than a cup . Thus , hot tea or coffee evaporates faster and cools faster in a saucer than in a cup . Therefore , we are able to sip hot tea or milk faster from a saucer than a cup .
Q. 17. What type of clothes should we wear in summers ? [ NCERT Q. 5 , Page 10 ]
Ans . We should wear light coloured cotton clothes in summers because :
( i ) In summers , we sweat a lot . Cotton is a good absorber of water . Thus , it absorbs sweat from our body and exposes the sweat to the atmosphere , making its evaporation faster and keep cool and comfortable . [ 1 ]
( ii ) During this evaporation , particles on the surface of the liquid gain energy from our body surface , making the body cool . [ 1 ]
( iii ) Light coloured clothes are poor absorber of heat and would be better for summer . [ 1 ]
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NCERT Solutions For Class 9 Science Chapter 1 Matter In Our Surroundings contains extremely important points, and for each chapter, each concept has been simplified to make it easier to remember and increase your chances of achieving excellent exam results. Exam Preparation References Here are some tips on how these solutions can help you prepare for the exam.
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