Class 9 Science NCERT solutions of chapter 1- Matter in our surrounding
Why are Science NCERT solutions are so important of chapter 1 -Matter in our surroundings?,its answer is that Class 9 science chapter 1 -Matter in our surroundings is the basic chapter of chemistry part of the NCERT science textbook prescribed by CBSE for class 9 students. and NCERT Solutions of chapter 1 -matter in our surroundings is just an initiation in learning chemistry section of class 9 NCERT science textbook. Here all NCERT solutions of the chapter 1-Matter in our surroundings are explained beautifully by an expert of science as per the CBSE norms.
The second law of motion
The universal law of gravitational force
Chapter 2-Is matter around us pure NCERT solutions
Matter in our surroundings
Q1-Which of the following are matters? chair, air, love, smell, hat, almond, thaught, cold, cold drink, the smell of perfume.
Ans- Chair, air, smell, almond, the smell of perfume all follow the characteristics of the matter because as we know matter occupies space and has mass, all variety of smell is the gaseous state of the matter.
Q2-Give reasons for the following observation: the smell of hot sizzling food reaches you several meters away, but to get the smell of cold food you have to go close.
Ans-The kinetic energy of the particles of hot food increases, which mixes with the air and reaches us even it is several meters away but particles of cold food have not too much kinetic energy to mix up with the air and we don’t get its smell.
Q3-A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Ans- There is space between the particles of the matter this is the reason a diver is able to cut water in a swimming pool.
Q4-What are the characteristics of the particles of matter?
Ans- (i) Particles of matter have space between them.
(ii) Particles of matter are moving continuously.
(iii) Particles of matter attract each other.
Q5-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 the chimney, honey, water, chalk, cotton, and iron.
ANS- The given substance in the increasing order of their densities are
Air, exhaust from chimney, cotton, water, honey, chalk, iron
Q6- (a) Tabulate the differences in the characteristics of states of the matter.
|Solids have definite shape and volume||Have a definite volume but don’t have a definite shape, it takes the shape of vessels.||Don’t have definite shape and volume|
|Incompressible||Compressible to some extent.||Highly compressible|
|There is little space between the particles||Space between the particles is more than the solids.||Space between the particles is the greatest.|
|There is the strongest force of attraction between particles of solid.||The force of attraction between particles of liquids is lesser than the solids.||The force of attraction between particles of gases is negligible.|
|Particles of solid can not move freely.||Particles of gases move freely.||Particles of gas move freely in a random way.|
(b)Comment upon the following rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy, and density.
(b) Rigidity – Rigidity of a substance is the characteristic of a substance to resist any kind of deformation in its shape.
Compressibility-The characteristic of a substance that makes the change in its volume when it is pressurized.
Fluidity- The ability of the matter which makes it to flow easily.
Filling a gas container-When the gas is filled in a container,it takes the shape of the container.
Shape- Shape defines a definite boundary.
Kinetic energy- Kinetic energy is the energy possessed by a moving body.
Density- The density of the substance is mass per unit volume.
Q7- 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 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.
(a) There is little force of attraction between particles of gas, thus its particles move freely wherever space is available, it is the reason gas fills the vessel completely in which it is kept.
(b) The particles of gas move randomly in all directions, due to this characteristic its particles hit each other and also hit walls of the container by a force, therefore gas exerts pressure on the walls of the vessel.
(c) The particles of the wooden table do not move anywhere, it can not be compressed, it has definite shape and volume, so it is solid because it is having all the properties of solid.
(d) We can easily move our hand through the air because it has the greatest space between the particles, the space between the particles of the solid block of wood is little and it is rigid so we can not move our hand through it, for doing this one has to be expert in karate.
Q8-Liquids generally have a lower density as compared to solids. But you must have observed that ice floats on water, find out why?
Ans- When the temperature of the water is lowered its particles get closer to each other up to 4°C temperature, thereafter it is started to be crystallized, due to this phenomenon its particles arranged in such a way that its particles become further from each other as compared to the space between the particles of water, so the density of ice is lesser than water which causes ice floats on the surface of the water.
Q9-Convert the following temperature to the Celcius scale.
(a) 300 K
Ans . 10 = 273 K
(a) 300K = 300K ─ 273⁰C
300K = 27⁰C
(b) 573 K = 573K ─ 273⁰C
573K = 200⁰C
Q10- What is the physical state of water at :
(a) At 2500C water exist in the gaseous state.
(b) At 1000C water starts to change from liquid to gaseous state, so it exists in both liquid and gaseous state.
Q11- For any substance, why does the temperature remain constant during the change of the state.
Ans – The particles of matter which are bounded to one another by intermolecular forces, during the change of state the heat given to it is utilized to overcome these forces, therefore, the temperature remains constant until it is completely changed to another state of matter.
Q 12- Suggest a method to liquefy atmospheric gases.
Ans -By applying the pressure and reducing the temperature the atmospheric gases can be liquefied.
Q13- Why does a desert cooler cool better on a hot dry day?
Ans. As we know the water inside the desert cooler evaporates due to the wind generated by its fan, for getting evaporated the water inside it gets heat energy from the surroundings which makes surroundings cool. On a hot dry day the humidity of surroundings is lower due to which the rate of evaporation of water inside it increases, thereby cooling the surroundings more. That is why the desert cooler cools better on a hot dry day.
Q14- How does water kept in an earthen pot become cool during summers.
Ans- In an earthen pot there are pores, the water inside the pot evaporates through these pores, for evaporation of water the heat energy is absorbed from the water inside it, thereby making the water inside it cool. During summers the temperature becomes more and humidity becomes lower due to which rate of evaporation increases. That is why water inside an earthen pot becomes cool during summers.
Q15- Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Ans- When we put some acetone or petrol or perfume on our palm, it gets evaporated, for the evaporation, the heat is absorbed from our palm by the surroundings, this is the way how we feel our palm cool.
Q16- Why are we able to sip hot tea or milk faster from a saucer than a cup?
Ans. A saucer has a larger surface area than a cup, as we know when a liquid is the larger area the rate evaporation becomes fast, thereby making the tea or milk cool faster. That is why we able to sip hot tea or milk faster from a saucer than a cup.
Q17- What type of clothes should we wear during the summer?
Ans- We sweat more in summer so we should wear cotton clothes during the summer because cotton is a good absorber of the water. The sweat of our body is absorbed by cotton cloths exposed to the air around us, due to lower humidity and higher temperature the sweat of our body evaporates faster. For the evaporation the heat is taken from the surface of our body, thereby making the body cool.
Q18- Convert the following temperature to the Celsius scale.
(a) As we know 0⁰C = 273K
293K = 293K ─ 273⁰C = 20⁰C
(b)470K = 470 ─ 273 = 197⁰C
Q19- Convert the following temperatures to the kelvin scale.
(a) We know 0⁰C = 273k
25⁰C = 273 + 25 = 298K
(b)373⁰C = 373 + 273 = 673K
Q20- Give reasons for the following observation.
(a)Naphthalene balls disappear with time without leaving any solids.
(b)We can get the smell of perfume sitting several meters away.
(a)The process of changing directly from solid to gas or gas to solid is known as sublimation, the naphthalene balls undergo sublimation easily, it is through this process completely transformed into a gas without leaving any solids.
(b) Gaseous particles have higher speed and larger space between the particles, so the particles of perfume easily diffuse into the air which enables us to smell it from a distance.
Q21.Arrange the following substance in order of their increasing order of force of attraction between the particles.—Water, Sugar, oxygen.
Ans- Water is a liquid, sugar is solid and oxygen is a gas, we know the force of attraction is strongest in between the particles of the solid, force of attraction between the particles of liquid is lesser and least in gas. So the increasing order will be oxygen, water, sugar.
Q22 – What is the physical state of water in the following temperature.
(a)At 250C, water is in a liquid state.
(b)At 0⁰C, water exists in both liquid and solid states because it is the temperature at which water gets required latent heat of the fusion, and then solid-state of water starts to change into liquid form of water.
(c)At 100⁰C temperature, water exists in both states liquid and gaseous. At this temperature water gets required latent heat of vaporization, then starts to change into a gaseous state.
Q23.Give two reasons to justify
(a) Water at room temperature is liquid.
(b) The iron almirah is solid at room temperature.
( a) Water is liquid at room temperature because it is having all the characteristics of the liquid.
It flows at room temperature.
It has a definite volume.
(b)The iron almirah is solid at room temperature because.
It has a definite shape and volume at room temperature.
It is rigid and can not be compressed at room temperature.
Q24. Why is ice at 273K more effective in cooling than water at the same temperature?
Ans- Ice at 273 K has lesser energy as compared to water at 273K, water has an extra latent heat of fusion, so it will definitely be hotter than ice. It is the reason at the same temperature of 273K, ice because of less energy will be cooler than water.
Q25. What produces more severe burn, boiling water or steam.
Ans-Steam has more energy as compared to water at the same temperature because steam has an additional latent heat of vaporization, that is why steam produces more severe burn as compared to boiling water.
Q26- Name A, B, C, D, E and F in the following diagram showing the change in states.
A: Melting or fusion or liquefication
B: Evaporation or vaporization
D:Solidification or freezing