CHAPTER 1
MATTER IN OUR SURROUNDINGS
Chapter 1 MATTER IN OUR SURROUNDINGS of SCIENCE NCERT of CLASS 9 complete solution and some important points are given. This will help student to better understand the topic and can easily solve the problems related to CHAPTER 1 MATTER IN OUR SURROUNDINGS Class 9.
SOME IMPORTANT POINTS OF CHAPTER 1 MATTER IN OUR SURROUNDINGS
I) Melting point:- The temperature at which solid melts to became a liquid at the atmospheric pressure is called its melting point.
II) Fusion:- The process of melting that is change of solid state into liquid states is also known as fusion.
III) Latent Heat Of vapourisation:- The amount of heat energy that is required to change 1kg of liquid into gas(vapour) at its boiling point is known as latent heat of vapourisation.
IV) Latent heat of Fusion:- The amount of heat energy that is required to change 1kg of solid into liquid at atmospheric pressure as its melting point is known as latent heat of Fusion.
V) Boiling Point:- The temperature at which a liquid starts boiling at the atmosphere pressure is known as its boiling point.
VI) Latent heat:- It is a heat energy which is absorbed by ice without showing any rise in temperature is known as latent heat.
VII) Sublimation:- A change of state directly from solid to gas without changing into liquid state (or vice versa) is called Sublimation.
These are some important points of CHAPTER 1 MATTER IN OUR SURROUNDINGS of Class 9 Science NCERT.
Here is the answer of textbook Questions of Chapter 1 MATTER IN OUR SURROUNDINGS.
Block questions (PageNo. - 3)
Ques 1. Which of the following are matter?
Chair,Air,love,smell,hate,almonds,thought,cold,lemon, water,smell of perfume.
Ans. Chair,air,almonds, smell of perfume.
Ques 2. Give reasons for the following observation:-
The smell of hot sizzling food reaches you several metres away,but to get the smell from cold food you have to go close.
Ans. This happens because the rate of diffusion of hot gases(released by the hot food) is much faster as in case of cold food.
Ques 3. A diver is able to cut through water in a swimming pool,which property of matter does this observation shows?
Ans. This shows that through there is strong force of attraction between the particles of water in rest position but by applying more force,diver is able to cut through water in a swimming pool.
Ques 4. What are the characteristics of particles of matter?
Ans. I) Particles of matter are very small.
II) Particles of matter have space between them.
III) Particles of matter are continuously moving.
IV) Particles of matter attract each other.
(Page No.6)
Ques 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.
Ans. Air < exhaust from chimneys < cotton < water < honey < chalk < iron.
Ques 2. a) Tabulate the difference in the characteristics of states of matter.
b) Comment upon the following rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
Ans. a) (a) The difference in the characteristics of the three states of matter.
| Characteristics | Solid | Liquid | Gas |
| Shape | Fixed shape | No Fixed shape | No Fixed shape |
| Volume | Fixed volume | Fixed volume | No Fixed volume |
| Intermolecular force | Maximum | Less than solids | Very less |
| Intermolecular space | Very less | More than solids | maximum |
| Rigidity/Fluidity | Rigid/cannot flow | Can flow/not rigid | Can flow/not rigid |
| Compressibility | negligible | compressible | Highly compressible |
Ans b) Rigidity:- The tendency of a substance to retain/ maintain their shape subjected to outside force.
Compressibility:- The matter has intermolecular space.The external force applied on the matter can bring the article closer.This property is called Compressibility.Gases and liquid are compressible.
Fluidity:- The tendency of particles to flow is called fluidity. Liquid and gases are flow.
Filling of Gas container:- Gases have particles which vibrate randomly in all the directions. The gas can fill the container.
Shape:- Solid have maximum intermolecular force and definite shape whereas liquid and gases take the shape of container.
Kinetic energy:- The energy possessed by particles due to their motion is called kinetic energy.Molecules of gases vibrate randomly as they have maximum kinetic energy.
Density:- It is defined as mass per unit volume,the solid have highest density.
Ques 3. Give reason:-
a) A gas fill completly the vessel in which it is kept.
b) A gas exerts pressure on the wall 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.
Ans.a) It is so because the particles of Gas have high kinetic energy and they are free to move.
b) In the gaseous state the particles move about randomly at high speed due to this random movement particles hit each other and also the wall of the container. Thus, the gas exerts pressure on the wall of the container.
c) It has definite shape, distinct boundaries,fixed volume and negligence compressibility.
d)It is because the particles of air have large space between them and very less force of attraction. While in a block of wood particles are closely packed
Ques 4. Liquid generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Ans. Ice is solid but its density is lower than water due to its structure. The molecules in solid makes a cage like structure with lot of vacant space,this makes ice float on water.
(Page No. 9)
Ques 1. Convert the following temperature to celsius scale:-
a)300k
b) 573k
Ans. a)0°C = 273k
300k = 300-273
=27°C
b) 0°C = 273 k
573k = 573-273
= 300°C
Ques 2. What is the physical state of water at:-
a) 250°C
b) 100°C
Ans.a) Water will be gas(water vapour) at 250°C.
b) Water will be liquid and gas both.
Ques 3. For any substance,why did the temperature remain constant during the change of stale?
Ans. It is so because the heat get used up in changing the state of overcoming the force of attraction between the particles.
(Page No.10)
Ques 1. Why does a desert cooler cool better on a hot dry day?
Ans. On the hot dry day temperature is high and humidity is low. So the rate of evaporation of heat is faster. Particles of water absorbs energy from the surrounding to regain energy lost during the evaporation. This absorption of energy from surrounding makes the surrounding cool.
Ques 2. How does the water kept in an earthern pot became cool during summer?
Ans. It is because earthern pot contains mining holes it abosrbs heat from the water and evaporate in the surrounding and thus makes the water cool.
Ques 3. Why does our palm feel cold when we put some acetons on petrol or perfume on it?
Ans. The particles of acetone on perfume gain energy from our palm on surrounding and evaporation cause the palm to feel cool.
Ques 4. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Ans . It is so because the surface area of saucer is more than a cup. So, the rate of evaporation of heat is faster from a saucer rather than a cup.
Ques 5. What type of clothes should we wear in summer?
Ans. We should wear cotton clothes in summer because cotton is a good absorber of water which helps is absorbing sweat and exposing it into the atmosphere for easy evaporation.
Exercise Questions-
Ques 1. Convert the following temperature to celsius scale:
a) 293K
b) 470K
Ans. a) 0°C = 273 k
293K= 293-273
=20°C
b) 0°C = 273k
470°C = 470-273
= 197°C
Ques 2. Convert the following temperature to the Kelvin scale:
a) 25°C
b) 373°C
Ans. a)0°C= 273k
25°C= 25+273
=298K
b) 0°C=273k
373°C=373+273
=646K
Ques 3. Give reason for the following observation:-
a) Napthalene balls disappear with time with out leaving any solid.
b) We can get the smell of perfume sitting several metres away.
Ans.a) Napthalene balls disappear with time with out leaving any solid because of the process of sublimation. Napthalene balls are converted into vapour (gas).
b) We can get the smell of perfume sitting several metres away because of the process of diffusion. The particles of perfume mixed with the surrounding (air).
Ques 4. Arrange the following substance in increasing order of force of attraction between the particles- water,sugar,oxygen.
Ans. Oxygen(gas)<water<(liquid)<sugar(solid) increasing order of force of attraction.
Ques 5. What is the physical state of water at-
a)25°C
b)0°C
c)100°C
Ans. a) liquid
b)ice(solid)
c) water vapour (gas)
Ques 6. Give two reasons to justify:
a) Water at room temperature is a solid.
b) An iron almirah is a solid at room temperature.
Ans.a) I) It is so because water has no fixed shape but it is has fixed volume.
II) It takes the shape of the container.
b) I) It is highly rigid and it has definite shape.
II) It has fixed volume and distinct boundaries.
Ques 7. Why is ice at 273k more effective in cooling than water at the same temperature?
Ans. Ice at 0°C or 273k is more effective in cooling than water at the same temperature because ice is a solid and during the conversion of solid into liquid,energy is with drawn, surrounding resulting in cooling. Therefore,ice is more effective in cooling than water at the same temperature.
Ques 8. What produces more severe burn, boiling water on stream?
Ans. Stream produces severe burn because particles of stream have absorb extra energy in the form of latent heat of vapourisation.
Ques 9. Name A,B,C,D,E and F in the change in its state.
Ans. A= Fusion or Melting
B= Evaporation or vapourisation
C= Condensation
D=Solidification
E= Sublimation
F= Sublimation
This is the complete solution of CHAPTER 1 MATTER IN OUR SURROUNDINGS. This is according to latest syllabus of CBSE 2020-21.
Here's some extra questions are given according to CHAPTER 1 MATTER IN OUR SURROUNDINGS of class 9 Science NCERT.
Ques 1. What is Matter?
Ans. Matter is something which occupy space and have mass and volume.
Ques 2. What is Diffusion?
Ans. Intermixing of particles of two different types of matter their own is called diffusion.
Ques 3. Why is rubber band called a solid through it changes its shape on stretching?
Ans. A rubber band changes shape under force and regains the same shape when the force is removed. If excessive force is applied, it breaks.
Ques 4. Why are sugar and salt crystals called solid through they take the shape of the jar.
Ans. The shape of each individual sugar or salt crystal remains fixed, whether we take it in our hand put it in a plate or in a jar.
Ques 5. Why sponge is considered as a solid through it can be compressed?
Ans. A sponge has minute holes in which air is trapped when we press it the air is expelled out and we are able to compress it.
Ques 6. What are the properties of solid?
Ans. Solid have a definite shape, distinct boundaries, fixed volume, negligible compressibility and they are rigid.
Ques 7. Why is rate of diffusion higher in liquid than that of solid?
Ans. The rate of diffusion of liquid is higher than that of solid to fact that in the liquid state. Particles move freely and have greater space between each other as compared to particles in the solid state.
These are some extra Questions of Chapter 1 MATTER IN OUR SURROUNDINGS of class 9 Science NCERT.
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