Matter in Our Surroundings | Class 9 Science | NCERT Science Chapter 1 | In-Text Questions & Answers | Exercises Questions & Answers | Notes & pdf
Q1. How do you define matter in our surroundings?
Everything in our surroundings which has volume and mass is called matter. Matter is made up of very very small particles. Particles are continuously moving due to their kinetic energy. These particles have spaces between them. For example, take a glass of water. Add one cup of sugar into it and mix well. Does the level of water in glass rise? Of course, not. Why? Because the particles of sugar occupy space between the particles of water. This intermixing phenomenon of different types of matter is called diffusion. Generally heating accelerates diffusion.
Q2. How many states of matter in our surroundings?
Matter in our surroundings has three states i.e. Solid, Liquid & Gas.
Q3. What is solid? What are the properties of solid?
The matters that have fixed volume, definite shape & distinct boundary in normal condition are called solids. For example, Silver, Wood, Stone, Sand, Copper, Salt etc.
a) Shape and volume of solids remain unchanged at certain pressure and temperature.
b) It is rigid. It has negligible compressibility. Applying high outside pressure almost does not change the volume of solid. Rather it may break.
c) Generally solids do not vaporize. But some solids like Iodine, Naphthalene etc. slowly turns into gas.
d) At normal temperature and pressure some solids (e.g. Salt, Phosphorus etc.) turn into crystalline.
Q4. What is liquid? What are the properties of liquid?
The matters that have fixed volume but no shape in normal condition are called liquids. For example, Water, Oil etc. Liquid is also called fluid because it can flow. Liquid also changes shape.
a) It is not rigid like solid. At certain pressure and temperature, volume of liquid is fixed and it takes the shape of the container in which it is kept.
b) Generally volume changes to a small extent if outside pressure is applied.
c) Applying heat changes the volume of liquids. If we continuously apply heat on liquid, temperature will start to increase and gradually it reaches boiling temperature. After that liquid starts turning into gas.
d) If we mix different types of liquids, then total volume will be summation of the volume of each type of liquid.
e) Liquids of similar properties and characteristics mix with each other.
f) Solids, liquids and gases can diffuse into liquids. Diffusion in liquids happens easily than solids because particles in liquid have greater space between them than solid particles.
Q5. What is gas? What are the properties of gas?
The matters that have no fixed volume and shape in normal condition are called gases. It takes the shape of the container. For example, Oxygen, Air, Nitrogen, Hydrogen etc.
a) Gases have no shape and volume. It takes the shape of container where it is kept.
b) If gases are not kept in container, it will expand all over around.
c) Generally volume of the gas increases with the rise in temperature.
d) Applying outside pressure decreases the volume of the gas.
e) Basically density of the gas depends on the pressure and temperature of the gas.
f) Some gases mix with each other at any ratio. For example, Air which contains Nitrogen, Oxygen, Carbon dioxide etc.
Q6. Why matter in our surroundings is found in three states?
The tiny particles form a matter. There is space between these particles which is called inter-molecular space. The particles attract each other. This attracting force is called cohesion. The three states of matter depend on this cohesion force.
Effect of cohesion force: Cohesion force is very high in solids. Inter-molecular space is very less in solids. That is why solid has fixed shape and volume. If temperature of solid increases, then movement of particles also increases. When temperature reaches melting point, movement of particles (due to kinetic energy) becomes high and it overcomes cohesion force. As a result inter-molecular space between particles increases. Thus solid starts to turn into liquid. This phenomenon is also called fusion.
Further continuation of increasing of the temperature, accelerates the movement of the particles. So inter-molecular space between particles increases. This causes more decrease in cohesion force. When temperature reaches boiling point, particles start to leave each other due to low and weak cohesion force. Then liquid starts to turn into gas.
Q7. What are boiling point, melting point, freezing point and condensation Point?
Boiling Point: Boiling point of a liquid is the temperature at standard atmospheric pressure (i.e. 760 mm Hg) at which that liquid starts vaporising or boiling. For example ⇒ Water – 100OC, Copper – 2595 OC, Zinc – 907 OC, Iron – 3253 OC etc.
Melting Point: Melting point of a solid is the temperature at standard atmospheric pressure (i.e. 760 mm Hg) at which that solid starts melting and turning into liquid. For example ⇒ Water – 0OC, Copper – 1083 OC, Zinc – 420 OC, Iron – 1535 OC etc.
Freezing Point: Freezing or solidification of a liquid is the temperature at standard atmospheric pressure (i.e. 760 mm Hg) at which that liquid starts freezing or solidifying and turning into solid. Freezing point and melting point of a particular matter are same .
Condensation Point: Condensation point of a gas is the temperature at standard atmospheric pressure( i.e. 760 mm Hg) at which that gas starts condensing and turning into liquid. Boiling point and condensation point of a particular matter are same .
Q8. What is latent heat?
At first take ice in a beaker. Then put a thermometer into it.
First phase ⇒ Temperature is 0oC (273 K or 273 Kelvin). There is only ice in beaker but no water. Let start heating.
Second phase ⇒A portion of ice turns into water and other portion still is in ice form. At this condition thermometer indicates 0oC (273 K) temperature.
Third phase ⇒ Let continue heating and finally total ice turns into water. Still thermometer indicates 0oC (273K) temperature at this condition.
We observe that temperature remains unaltered during the whole process of changing of states i.e. from ice to water. During this process, heating is done. Then where this heat has gone? This heat is called latent heat and it is used to change the state of matter.
Temperature remains unaltered during changing of states of matter i.e. melting, solidification, boiling and condensation. Melting and boiling requires heat to change the state of matter. On the other hand, solidification and condensation requires heat extraction to change the state of matter.
Q9. What is latent heat of melting and solidification?
a) Latent heat of solidification: The heat required to change a particular matter from solid to liquid without changing the temperature is the latent heat of melting or fusion of that particular matter. Latent heat of ice is 3.36×105 J/Kg which means that for changing of 1 kg ice into water at 0OC, total heat requirement is 3.36X105 J.
b) Latent heat of solidification: The amount of heat to be extracted to change a particular matter from liquid to solid without changing the temperature is the latent heat of solidification of that particular matter. Latent heat of water to ice conversion is 3.36X105 J/Kg which means that for changing of 1 kg water into ice at 0OC, total heat extraction requirement is 3.36X105 J.
#Latent heat of melting and solidification are always same of a particular matter
i. Calculate the heat required to turn 20 Kg ice of 0 oC into water of 0 oC. Given that, latent heat of melting of ice 3.36×106 J/Kg .
Given that, latent heat of melting of ice 3.36×106 J/Kg. Heat required to turn 1 Kg ice into water = 3.36×106 Joule. So heat required to turn 20 Kg ice into water = 20 x 3.36 x 106 Joule = 67.2 x 106 Joule.
ii. Calculate the heat required to turn 500 gram ice of 0oC into water of 0oC. Given that, latent heat of melting of ice 80 Cal/g.
All units given here are indeed in C.G.S system. Heat required to turn 1 gram ice into water = 80 Calorie. So the heat required to turn 500 gram ice into water = 500 x 80 Calorie = 40000 Calorie.
Q10. What is latent heat of boiling and condensation?
a. Latent heat of Boiling or Vaporisation: The amount of heat required to change a particular matter from liquid to vapour without changing the temperature is the latent heat of boiling or vaporisation of that particular matter. Latent heat of water to steam is 2.26X106 J/Kg i.e. at 100OC, 1Kg water requires 2.26X106 J heat to turn into steam.
b. Latent heat of Condensation: The amount of heat to be extracted to change the state of a particular matter from vapour to liquid without changing the temperature is the latent heat of condensation of that particular matter. Latent heat of steam to water conversion is 2.26×106 J/Kg i.e. at 100OC, 1Kg steam requires extraction of 2.26×106 J heat to turn it into water.
Latent heat of boiling and condensation are always same of a particular matter
i. Calculate the heat extraction required to turn 7 Kg steam of 100 oC into water of 100 oC. Given that, latent heat of condensation of steam is 2.26×106 Joule.
Heat extraction required to turn 1 Kg steam into water = 2.26×106 Joule. Similarly, heat extraction required to turn 7 Kg steam into water into water = 7 x 2.26 x 106 Joule = 15.82 x 106 Joule.
ii. Calculate the heat required to turn 12 Kg ice of 0 oC into steam of 100 oC. Given that ⇒ latent heat of steam = 2.26×106 Joule/Kg, latent heat of water = 4.2 x103 Joule/Kg/oC, latent heat of ice = 3.36×106 Joule/Kg.
Heat required to turn 12 Kg ice of 0oC into water of 0oC = 12 x 3.36 x 106 Joule = 40.32 x 106 Joule. Hence heat required to turn 12 Kg water of 0 oC into water of 100 oC = 12 x (100-0) x 4.2 x 103 Joule = 5040 x 103 Joule = 5.04 x 106 Joule.
Heat required to turn 12 Kg water of 100oC into steam of 100oC = 12 x 2.26 x 106 Joule = 27.12 x 106 Joule. Hence, total heat required to turn 12 Kg ice of 0 oC into steam of 100 oC = [(40.32 x 106 ) + (5.04 x 106) + (27.12 x 106)] Joule = 72.48 x 106 Joule.
Q11. Does pressure affect the changing of state of matter?
Pressure & temperature determine states of matter. We know that outside pressure negligibly affects solid & liquid. But it affects gas too much as gas has high compressibility. High outside pressure with reduction in temperature liquefies gas. For example, cooking gas i.e. LPG (Light Petroleum Gas), medical oxygen, CNG (Compressed Natural Gas) fuel etc. In all these cases, gases are liquefied under high pressure. Dry ice i.e. solid carbon dioxide is another example. Dry ice is formed & kept under very high pressure. A slight decrease in pressure, about 1 atm, converts solid carbon dioxide to gaseous state.
Q12. What do you mean by the atmospheric pressure?
Q13. What is the relation between Kelvin & Celsius?
We learnt SI system of unit in units used in science chapter. The SI unit of temperature is Kelvin (named after British physicist William Thompson ). It is taken that 00C is equal to 273.15 Kelvin ≃ 273 K.
So to convert from 0C to K, we need to add 273 with the value in 0C. For example –100C = (10+273) K = 283 K
1250C = (125+273) K = 398 K
– 500C = (-50+273) K = 223 K
-1000C = (-100+273) K = 173 K
Similarly, to convert from K to 0C, we need to subtract 273 from the value in K scale. For example –
500 K = (500-273) 0C = 227 0C
350 K = (350-273) 0C = 77 0C
200 K = (200-273) 0C = -73 0C
250 K = (250-273) 0C = -23 0C
Q14. What is evaporation? Which factors accelerate evaporation in our surroundings?
Evaporation is a phenomenon where liquid turns to vapour slowly in normal condition. It is an example of changing the state of liquid at temperature much below the boiling point. Water from various sources in our surroundings such as ponds, rivers, sea evaporates. But the temperature never reaches boiling point. Drying of wet clothes is also an example of evaporation. Following factors affect evaporation.
- Decrease in humidity accelerates evaporation.
- Evaporation accelerates when temperature of liquid and air increases.
- Increase in surface area also accelerates evaporation.
- Evaporation decelerates when air pressure increases.
- Increase in air flow also accelerates evaporation.
- Matter with low boiling point evaporates fast. For example, Spirit, Petrol, Alcohol etc.
Q15. What is sublimation & deposition?
Matters like Camphor, Iodine, Naphthalene etc. slowly turns into gases in normal condition. This phenomenon is called sublimation. Heating accelerates sublimation process. If these gases are cooled, then they turn into solid again. This reverse phenomenon is called deposition. Sublimation & deposition are the direct conversion from solid to liquid state & vice versa without going through liquid stage.
Q16. Is there any other state of matter except solid, liquid or gas?
Apart from three states of matter i.e. solid, liquid & gas of matter, scientists have added two more states. These are – a) plasma, & b) Bose-Einstein condensate.
Plasma ⇒ Plasma contains super excited & super energetic particles in the form of ionised gas. The cases of fluorescent tube & neon bulbs are examples of plasma state of matter. There is helium gas in fluorescent tube & neon gas in neon bulbs. When we switch on, the gas inside fluorescent tube/neon bulbs gets charged i.e. turns ionised. It results creation of plasma glowing inside fluorescent tube/neon bulbs with a special colour. The colour depends on the types of gases. Glowing of the Sun & other stars are also example of plasma which is created because of very very high temperature.
Bose-Einstein Condensate ⇒ Formation of Bose-Einstein condensate is done by cooling a gas of extremely low density to super low temperatures. That extreme low density is about one-hundred-thousandth the density of normal air. German scientist Albert Einstein predicted this fifth state of matter which is based on calculations done by Indian physicist Satyendra Nath Bose.
In-Text Questions & Answers | Matter in Our Surroundings | NCERT Class 9 Science Chapter 1
In-Text Questions & Answers | Matter in Our Surroundings | NCERT Class 9 Science Chapter 1 | Page No. 03:
1) Which are matter – Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume?
Chair, air, almonds, lemon water, smell of perfume are matter. All these satisfy various characteristics of matter i.e. mass, volume, shape, states (solid / liquid / gas) etc. But love, smell, hate, thought & cold do not satisfy any criteria of matter. So these are not matters.
2) Give reasons for the 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.
Diffusion is the phenomenon of inter-mixing of particles of different matters. Also heating accelerates it. That is why the smell of hot sizzling food reaches us at greater distance. But we have to go close to get the smell from cold food.
3) A diver is able to cut through water in a swimming pool. Which property of matter does this observation?
It expresses that liquid state of matter is made up of particles.
4) What are characteristics of the particles in matter?
The particles are continuously moving due to kinetic energy. A force of attraction exists between them. The particles have space between them.
In-Text Questions & Answers | Matter in Our Surroundings | NCERT Class 9 Science Chapter 1 | Page No. 06
1. The mass per unit volume of a substance is called density (density = mass/volume) Arrange in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton & iron.
Air < Exhaust from chimneys < Cotton < Water < Honey < Chalk < Iron.
2a. Tabulate the differences in the characteristics of states of matter.
1. Solid has definite shape, fixed volume & distinct boundary.
1. Liquid has fixed volume but not fixed shape. It can flow & takes the shape of the container where it is kept.
1. Gas has no fixed shape. It is kept in closed container.
2. It is rigid & incompressible. Outside pressure negligibly changes the volume of solid.
2. Outside pressure changes the volume of liquid to a small extent.
2. It is basically highly compressible. Outside pressure changes the volume of gas to larger extent.
3. Force of attraction between particles in solid is high. Also space between particles is very very less.
3. Force of attraction between particles in liquid is less than solid. Also particles have greater space between them.
3. Force of attraction between particles in gas lowest. Also particles move freely in all direction.
4. Mass/Volume of solid i.e. density is high. It's particles possess less kinetic energy.
4. Mass/Volume of liquid i.e. density is lower than solid. It's particles possess higher kinetic energy than.
4. Mass/Volume of gas i.e. density is lowest. It's particles possess highest kinetic energy.
2b. Comment upon on: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy & density.
Rigidity ⇒ It is the ability to resist the change of shape.
Compressibility ⇒ It is the capability to be reduced in volume when outside pressure is applied.
Fluidity ⇒ It is the ability to flow.
Filling a gas container ⇒ The gas attains the shape of the container.
Shape ⇒ It expresses a fixed boundary.
Kinetic energy ⇒ This is attained by a particle due to it’s motion.
Density ⇒ It is mass/volume which describes mass per unit volume.
3a. Give reasons – a gas fills completely the vessel in which it is kept.
The force of attraction between particles in gas is very less & they move freely in all direction. So gas takes the shape of the container where it is kept.
3b. Give reasons – a gas exerts pressure on the walls of the container.
The particles in gas move freely in all direction & gas takes the shape of the container where it is. So gas exerts pressure on the walls of the container.
3c. Give reasons – a wooden table should be called s solid.
The matter that has fixed volume, definite shape & distinct boundary is solid. A wooden table satisfies all these criteria. So it is a solid.
3d. Give reasons – We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.
Wood is solid & rigid. Space between particles in it is very very less. On the other side, air is a gas. It has spaces between it’s particles. That’s why we can easily move our hand in air but not in case of wood. So we need karate expert in case of wood.
4. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Generally density of solid is higher than density of liquid. But in this case, the density of ice, though solid, is lower than the density of water. So the volume of ice is more than that of water for a certain quantity. Therefore, ice floats on water due to having large volume & lower density.
In-Text Questions & Answers | Matter in Our Surroundings | NCERT Class 9 Science Chapter 1 | Page No. 09
1. Convert the temperature to Celsius scale – a) 300 K, b) 573 K.
a ⇒ 300 K = (300-273) oC = 27 oC, b ⇒ 573 K = (573-273) oC = 300 oC.
2. What is the physical state of water – a) 250oC, b) 100oC.
a ⇒ Boiling point of water is 100 oC. So the water will be gaseous state at 250 oC (>100 oC).
b ⇒ Water boils at 100 oC. It takes latent heat & turns into vapour. So at 100 oC, water may exists in both state i.e. water (liquid) & vapour (gas).
3. Why temperature remain constant during change of state for any substance?
Because the heat supplied to increase the temperature is used as latent heat. Latent heat converts the state of the substance keeping the temperature constant. So the supplied heat can not increase the temperature until the whole substance changes from one state to another.
4. Suggest a method to liquefy atmospheric gases in our surroundings.
Applying outside pressure with reduction in temperature can liquefy atmospheric gases.
In-Text Questions & Answers | Matter in Our Surroundings | NCERT Class 9 Science Chapter 1 | Page No. 10
1. Why does a desert cooler cool better on a hot dry day?
At first we should know how a desert cooler works. It has aerated grass pads in three sides & a fan on the front side. Water is circulated along three sides in it. Hot air enters into the cooler & helps the water evaporating. Water gains required heat for evaporation from the hot air. This action cools the hot air which is finally pushed into the room. Also we know that decrease in humidity accelerates evaporation. A hot dry day indicates high temperature & low humidity. This condition is good for quick evaporation which ultimately gives better cooling effect.
2. How does the water kept in an earthen pot or ṁatka become cool during summer?
The pot or matka has many minute pores because it is made of mud. The water inside the pot evaporates through the pores. It takes required heat for evaporation from the water inside the pot & the pot itself. This continuous evaporation makes the loss of heat from both the earthen pot & the water inside the pot. As a result, the water becomes cool in few hours.
3. Why does our palm feel cold when we put some acetone or petrol or perfume on it?
All these matter i.e. acetone, petrol & perfume have low boiling point. Also acetone is a volatile substance. These characteristics accelerate their evaporation. When we put these matter on our palm, it starts evaporating. During evaporation, these matter takes required heat from our palm & surroundings. Thus our palm feels cold.
4. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Larger surface area accelerates evaporation. The surface area of a saucer is greater than a cup. Hence, hot tea or milk from the saucer evaporates & cools faster than the cup. As a result, we can sip hot tea or milk from a saucer rather than a cup.
5. What type of clothes should we wear in summer?
We should wear cotton clothes. Because cotton clothes absorb sweat from our body very easily. And it exposes the absorbed sweat to the atmosphere which basically accelerates the evaporation of sweat. The sweat takes required energy from our body for its evaporation. That action makes our body cool & comfortable. We also prefer cotton clothes of light colours as light colours are poor absorber of heat.
Exercises Questions & Answers | Matter in Our Surroundings | NCERT Class 9 Science Chapter 1
1. Convert to Celsius scale – a) 293 K, b) 470 K.
a ⇒ 293 K = (293-273) oC = 20 oC, b ⇒ 470 K = (470-273) oC = 197 oC.
2. Convert to Kelvin scale – a) 25oC, b) 373oC.
a ⇒ 25 oC = (25+273) K = 298 K, b ⇒ 373 oC = (373+273) oC = 646 oC.
3a. Give reasons ⇒ naphthalene balls disappear with time without leaving any solid.
Sublimation is direct conversion of a solid to gas at normal condition without going through liquid stage. naphthalene shows this property. So naphthalene evaporates with time without leaving any solid.
3b. Give reasons ⇒ We can get the smell of perfume sitting several meters away.
The particles in gas move freely & randomly at any direction. When we spray a perfume, it turns into gas from liquid. After that it’s particles diffuse in air very easily. That is the reason for getting the smell of perfume sitting several metres away.
4. Arrange in increasing order of forces of attraction between the particles – water, sugar, oxygen.
If we consider in increasing order of forces of attraction, we get Gas < Liquid < Solid. So the answer is Oxygen < Water < Sugar.
5. What is the physical state of water at – a) 25oC , b) 0oC , c) 100oC.
In case of water ⇒
OoC ⇒ freezing & melting point.
100oC ⇒ boiling & condensation point.
So ⇒ a- 25oC ⇒ water, b- OoC ⇒ both water & ice, c- 100oC ⇒ both water & steam.
6a. Give reasons – Water at room temperature is a liquid.
Freezing & boiling points of water are OoC & 100oC. Our room temperature is in the range of 20oC – 25oC. So water at room temperature is liquid.
6b. Give reasons – an iron almirah is a solid at room temperature.
Melting point of iron i.e. when iron starts turning into liquid is 1535oC. Therefore, an iron almirah is solid at room temperature (20oC – 25oC).
7. Why is ice at 273 K more effective in cooling than water at same temperature?
Ice needs latent heat to turn into water at 273 K. At 273 K, only ice will take heat from surroundings because water is already at same temperature. So ice is more effective than water in cooling at 273 K.
8. What produces more severe burns, boiling water or steam?
Temperature of boiling water & steam is same i.e. 100oC. But steam possesses more heat than boiling water. Because boiling water takes latent heat & turns into steam or vapour. So steam produces more severe burns that boiling water.
9. Name A, B, C, D, E & F in the following diagram.
A ⇒ Melting, B ⇒ Boiling, C ⇒ Condensation, D ⇒ Solidification or Freezing, E ⇒ Sublimation, F ⇒ Deposition or De-sublimation.
Matter in Our Surroundings – To Be Continued – Matter in Our Surroundings