CBSE Chemistry IX Matter in our surrounding Chemistry solved questions

Q.1 Camphor disapperars without leaving any residue. Explain?Ans. Camphor disappears without leaving any residue because of sublimation, as it changes its statedirectly from solid to gas without changing to liquid.Q.2 Why do we feel cool when we touch a piece of ice?Ans. We feel cool because the temperature of ice is 0 deg C and our body’s temp is higher than 0 deg C.Q.3 Convert the following:-a) 573 KAns. 573-273= 300 deg Cb) 36 deg CAns. 273+36 = 309 Kc) 373 deg CAns. 373+273= 646 KQ.4 Both the process of evaporation and boiling involves the change of state from liquid to gas but still they are different from each other. Justify.Ans. Evaporation is diffeent from boiling as evaporation is a natural phenomenon, occurs on the surfaceof the water and also it is a slow process whereas boiling is an artificial phenomenon , it occurs in the bulkof the liquid and is a fast process.Q.5 Why is Kelvin considered as the best scale for measuring the temperature?Ans. Kelvin is the best scale for measuring the temperature because it has no max temp. and it canmeasure temperature to any extent.Q.6 How can you show that evaporation causes cooling?Ans. When we put some acetone on our hand , after sometime we will feel coolness on our hand becausethe action absorbs kinetic energy from our hand & evaporates and evaporation causes cooling.Q.7 What is the significance of boiling point & melting point of a substance?Ans. The significance of boiling point and melting point is that it shows the purity of the substance.Q.8 When we put CuSO4 in water, after sometime we find the soln. turns blue. Why? Also, on heating it, what change will occur?Ans. The solution turns blue because of diffusion. On heating the solution nothing will happenQ.9 How can you justify that table is a solid?Ans. When we apply force on the table it doesn’t change its shape because its intermolecules are tightlypacked , this shows that table is solid.Q.10 Arrange the following in decreasing order of force of attraction: Water, Salt, Oxygen,

Also, state the reason.Ans. Salt, Water, OxygenSalt has the maximum force of attraction as it is a solid, followed by water as it is a liquid. Oxygenis a gas so its force of attraction is the least.Q. 11 State characteristics of matter demonstrated by :a) diffusionAns. Diffusion involves movement of different particles so that they become intermixed uniformly .b) Brownian motionAns.It is thwe zig-zag movement of the small particles suspended in a liquid or a gas .Q.12 When an incense stick (agarbatti) is lighted in one corner of a room, its fragrance spreads in the whole room quickly.Which characteristic of the particles of matter is illustrated by this observation?Ans. Particles of matter are constantly moving.Q.13 The boiling point of alcohol isn 78 deg C. What is this temperature on Kelvin scale?Ans. K= Deg C + 273 = 78 + 273 = 351 KQ. 14 The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature?Ans. – 273 deg CQ. 15 What is Latent Heat of Fusion?Ans. The latent heat of fusion (or melting) of a solid is the quanity of heat in joules required to convert 1kilogram of the solid (at its melting point ) to liquid, without any change in temperature.Q. 16 Define latent heat of Vaporisation?Ans. The latent heatm of vaporisation of a liquid is the quantity of heat in joules required to convert 1kilogram of the liquid (at its boiling point ) to vapour or gas, without any change in temperature.

MCQ 9th science Matter In Our Surroundings MCQ1. Camphor is purified by the process of –

a. evaporation b. distillation c. sublimation d. filtration

2. LPG is used in the kitchens in our homes in the-

a. Solid form b. compressed form c. gaseous form d. none.

MATER IN OUR SURONDING DEFINATIONSMatter:

matter is commonly defined as the substance of which physical objects are composed, not

counting the contribution of various energy or force-fields, which are not usually considered to

be matter per se (though they may contribute to the mass of objects). Matter constitutes much

of the observable universe, although again, light is not ordinarily considered matter.

Unfortunately, for scientific purposes, "matter" is somewhat loosely defined. It can also be

defined as a physical substance that has mass and volume. 

Volume:

The volume of a solid object is the three-dimensional concept of how much space it occupies,

often quantified numerically. One-dimensional figures (such as lines) and two-dimensional

shapes (such as squares) are assigned zero volume in the three-dimensional space.

Mass:

Mass is a fundamental concept in physics, roughly corresponding to the intuitive idea of "how

much matter there is in an object". Mass is a central concept of classical mechanics and related

subjects, and there are several definitions of mass within the framework of relativistic kinematics

(see mass in special relativity and mass in General Relativity). In the theory of relativity, the

quantity invariant mass, which in concept is close to the classical idea of mass, does not vary

between single observers in different reference frames 

Diffusion:

In the second sense of diffusion is the spontaneous net movement of particles from an area of

high concentration to an area of low concentration through a semi-permeable membrane. For

example, diffusing molecules will move randomly between areas of high and low concentration

but because there are more molecules in the high concentration region, more molecules will

leave the high concentration region than the low concentration one. Therefore, there will be a

net movement of molecules from high to low concentration. Initially, a concentration gradient

leaves a smooth decrease in concentration from high to low which will form between the two

regions. As time progresses, the gradient will grow increasingly shallow until the concentrations

are equalized. 

Force:

force is what causes a mass to accelerate. It may be experienced as a lift, a push, or a pull. The

acceleration of the body is proportional to the vector sum of all forces acting on it (known as net

force or resultant force). In an extended body, force may also cause rotation, deformation, or an

increase in pressure for the body. Rotational effects are determined by the torques, while

deformation and pressure are determined by the stresses that the forces create. 

Pressure:

Pressure is the force per unit area applied on a surface in a direction perpendicular to that

surface. 

Density:

density is mass (m) per unit volume (V) — the ratio of the amount of matter in an object

compared to its volume. A small, heavy object, such as a rock or a lump of lead, is denser than

a larger object of the same mass, such as a piece of cork or foam. 

Kinetic energy: The kinetic energy of an object is the extra energy which it possesses due to its

motion. It is defined as the work needed to accelerate a body of a given mass from rest to its

current velocity. Having gained this energy during its acceleration, the body maintains this

kinetic energy unless its speed changes. Negative work of the same magnitude would be

required to return the body to a state of rest from that velocity. 

Speed:

speed is a quantity that measures the ratio of an evolution to time. Example: speed of

sedimentation, speed of economic growth, speed of chemical reaction etc. 

Melting point:

The melting point of a crystalline solid is the temperature range at which it changes state from

solid to liquid. Although the phrase would suggest a specific temperature and is commonly and

incorrectly used as such in most textbooks and literature, most crystalline compounds actually

melt over a range of a few degrees or less. At the melting point the solid and liquid phase exist

in equilibrium. When considered as the temperature of the reverse change from liquid to solid, it

is referred to as the freezing point. 

Atmospheric pressure:

Atmospheric pressure is the pressure at any point in the Earth's atmosphere. In most

circumstances atmospheric pressure is closely approximated by the hydrostatic pressure

caused by the weight of air above the measurement point. Low pressure areas have less

atmospheric mass above their location, whereas high pressure areas have more atmospheric

mass above their location. Similarly, as elevation increases there is less overlying atmospheric

mass, so that pressure decreases with increasing elevation. A column of air 1 square inch in

cross section, measured from sea level to the top of the atmosphere, would weigh

approximately 14.7 lbf. A 1 m² (11 sq ft) column of air would weigh about 100 kilonewtons

(equivalent to a mass of 10.2 tonnes at the surface). 

Latent heat:

Latent heat is the amount of energy in the form of heat released or absorbed by a substance

during a change of phase (i.e. solid, liquid, or gas), - also called a phase transition. 

Vaporisation:

Evaporation is the process by which molecules in a liquid state (e.g. water) spontaneously

become gaseous (e.g. water vapor). It is the opposite of condensation. Generally, evaporation

can be seen by the gradual disappearance of a liquid, when exposed to a significant volume of

gas.

Matter in our surrounding notes for class 9thMatter in our surrounding Explanatory notes

Introduction: 

Everything in this universe is made up of material which scientists have named “matter”. The air we

breathe, the food we eat, stones, clouds, stars, plants and animals, even a small drop of water or a particle

of sand– each thing is matter.

Early Indian philosophers classified matter in the form of five basic elements –air, earth, fire, sky and

water.

Modern day scientists have evolved two types of classification of matter based on their physical

properties and chemical nature.

Characteristics of Particles of Matter

1. PARTICLES OF MATTER HAVE SPACE BETWEEN THEM- when we make tea, coffee or

lemonade (nimbu paani ), particles of one type of matter get into the spaces between particles of the other.

This shows that there is enough space between particles of matter. Similarly particles of sugar, salt,

Dettol, or potassium permanganate get evenly distributed in water.

2. PARTICLES OF MATTER ARE CONTINUOUSLY MOVING- Particles of matter are continuously

moving, that is, they possess what we call the kinetic energy. As the temperature rises, particles move

faster. So, we can say that with increase in temperature the kinetic energy of the particles also increases.

3. PARTICLES OF MATTER ATTRACT EACH OTHER- Particles of matter have force acting between

them. This force keeps the particles together. The strength of this force of attraction varies from one kind

of matter to another.

States of Matter

1. THE SOLID STATE- all solids have a definite shape, distinct boundaries and fixed volumes, that is,

have negligible compressibility. Solids have a tendency to maintain their shape when subjected to outside

force. Solids may break under force but it is difficult to change their shape, so they are rigid.

2. THE LIQUID STATE- Liquids have no fixed shape but have a fixed volume. They take up the shape

of the container in which they are kept. Liquids flow and change shape, so they are not rigid but can be

called fluid. The rate of diffusion of liquids is higher than that of solids. This is due to the fact that in the

liquid state, particles move freely and have greater space between each other as compared to particles in

the solid state.

3. THE GASEOUS STATE- Gases are highly compressible as compared to solids and liquids. The

liquefied petroleum gas (LPG) cylinder that we get in our home for cooking or the oxygen supplied to

hospitals in cylinders is compressed gas. In the gaseous state, the particles move about randomly at high

speed. Due to this random movement, the particles hit each other and also the walls of the container.

Matter Can Change its State Water can exist in three states of matter–

·  Solid, as ice,

·  Liquid, as the familiar water, and

·  Gas, as water vapour.

EFFECT OF CHANGE OF TEMPERATURE

On increasing the temperature of solids, the kinetic energy of the particles increases. Due to the increase

in kinetic energy, the particles start vibrating with greater speed. The energy supplied by heat overcomes

the forces of attraction between the particles. The particles leave their fixed positions and start moving

more freely. A stage is reached when the solid melts and is converted to a liquid. The temperature at

which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

The melting point of ice is 273.16 K. The process of melting, that is, change of solid state into liquid state

is also known as fusion.

Solid ----heat----> Liquid  -------------------heat--> Gas 

          <---cool----                  <---cool---------------

So, we infer that the state of matter can be changed into another state by changing the temperature.

EFFECT OF CHANGE OF PRESSURE

Increasing or decreasing the pressure can change the state of matter. Applying pressure and reducing

temperature can liquefy gases.

For an example, Solid carbon dioxide (CO2) is stored under high pressure. Solid CO2 gets converted

directly to gaseous state on decrease of pressure to 1 atmosphere* without coming into liquid state. This

is the reason that solid carbon dioxide is also known as dry ice.

Thus, we can say that pressure and temperature determine the state of a substance, whether it will be

solid, liquid or gas.

Evaporation

Particles of matter are always moving and are never at rest. At a given temperature in any gas, liquid or

solid, there are particles with different amounts of kinetic energy. In the case of liquids, a small fraction

of particles at the surface, having higher kinetic energy, is able to break away from the forces of attraction

of other particles and gets converted into vapour. This phenomenon of change of a liquid into vapours at

any temperature below its boiling point is called evaporation.

FACTORS AFFECTING EVAPORATION

The rate of evaporation increases with–

• An increase of surface area: We know that evaporation is a surface phenomenon. If the surface area is

increased, the rate of evaporation increases. For example, while putting clothes for drying up we spread

them out.

• An increase of temperature: With the increase of temperature, more number of particles get enough

kinetic energy to go into the vapour state.

• A decrease in humidity: Humidity is the amount of water vapour present in air. The air around us cannot

hold more than a definite amount of water vapour at a given temperature. If the amount of water in air is

already high, the rate of evaporation decreases.

• An increase in wind speed: It is a common observation that clothes dry faster on a windy day. With the

increase in wind speed, the particles of water vapour move away with the wind, decreasing the amount of

water vapour in the surrounding.

HOW DOES EVAPORATION CAUSE COOLING?

In an open vessel, the liquid keeps on evaporating. The particles of liquid absorb energy from the

surrounding to regain the energy lost during evaporation. This absorption of energy from the surroundings

make the surroundings cold.

After a hot sunny day, people sprinkle water on the roof or open ground because the large latent heat of

vaporisation of water helps to cool the hot surface.

Why should we wear cotton clothes in summer?

During summer, we perspire more because of the mechanism of our body which keeps us cool. We know

that during evaporation, the particles at the surface of the liquid gain energy from the surroundings or

body surface and change into vapour. The heat energy equal to the latent heat of vaporisation is absorbed

from the body leaving the body cool. Cotton, being a good absorber of water helps in absorbing the sweat

and exposing it to the atmosphere for easy evaporation.

Why do we see water droplets on the outer surface of a glass containing ice-cold water?

Let us take some ice-cold water in a tumbler. Very soon we see water droplets on the outer surface of the

tumbler. The water vapour present in air, on coming in contact with the cold glass of water, loses energy

and gets converted to liquid state, which we see as water droplets.

Top concepts 1. Anything that occupies space and has mass is known as matter. 2. Matter is not continuous but rather consists of large number of particles. 3. Characteristics of Particle 

a.       Large number of particles constitutes matter. b.      Particles of matter are very small in size.  c.       Particles of matter have spaces between them  d.      Particles of matter are continuously moving 

4. Solids have definite shape, distinct boundaries and fixed volume5. Liquids have fixed volume but no fixed shape. 6. Gases neither have fixed shape nor volume. 7. Solids possess least compressibility.  8. Liquids possess higher compressibility than solids.9. Gases possess highest compressibility as compared to solids and liquids. 10. The process in which a solid changes to liquid state by absorbing heat at constant temperature is called fusion.  11. The temperature at which a solid melts to become a liquid at the atmospheric pressure is called as melting point.12. SI unit of temperature is Kelvin. T (K)= T (oC) +273 13. The hidden heat which breaks the force of attraction between the molecules during  change of state is called latent heat.14. Latent heat of fusion is the amount of heat energy required to change 1kg of solid into  liquid at its melting point. 15. The melting point of a solid is an indication of the strength of the force of attraction between its particles. 16. The temperature at which a liquid changes to solid  by giving out heat at atmospheric  pressure is called freezing point.17. The temperature at which a liquid starts boiling at the atmospheric pressure is known as  boiling point. 18. Latent heat of vaporization is the heat energy required to change 1kg of liquid to gas at atmospheric pressure at its boiling point.19. Boiling is a bulk phenomenon. 20. The phenomenon of change of a liquid into its gaseous state at any temperature below  its boiling point is known as evaporation.21. In evaporation, the conversion of liquid to gaseous state occurs at a much slower rate,  compared to boiling. 

22. Evaporation takes place only at the surface of the liquid while boiling can take place in  all parts of the liquid.23. Evaporation is surface phenomenon 24. Boiling is a bulk phenomena 25. The amount of water vapour present in the air is called humidity.26. Evaporation is a continuous or ongoing process.  27. Evaporation causes cooling. 28. The process of evaporation of water from the aerial parts of plants  especially leaves is  known as transpiration. 29. The rate of evaporation is affected by the surface  area exposed to atmosphere, temperature, humidity and wind speed.

30. Since evaporation is a surface phenomenon, therefore, it increases with an increase in surface area 31. Evaporation increases with an increase in temperature.32. Evaporation decreases with an increase in humidity 33. Evaporation increases with the increase in wind speed 34. The process in which a gas changes into liquid state by giving out heat at constant  temperature is called condensation. 

9th Sample Guess Extra score solved paper Matter in Our SurroundingsClass IX, Chemistry Solved Questions Chapter 1: Matter in Our Surroundings 1. what are the states of Matter around us?Ans The matter around us exists in three states— solid, liquid and gas.2. In which state of matter there will be maximum force of attraction between particles?Ans. The maximum forces of attraction between the particles will be in Solid state. 3. In which state of matter there will be maximum kinetic energy of the particles?Ans The maximum kinetic energy of the particles will be in gaseous state of matter.4.What do you mean by Sublimation Ans Sublimation is the change of gaseous state directly to solid state without going through liquid state, and vice versa.5. What do you mean by Latent heat of vaporization?Ans Latent heat of vaporization is the heat energy required to change1 kg of a liquid to gas at atmospheric pressure at its boiling point.6. What do you mean by Latent heat of fusion?

Ans Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at its melting point.7. In which unit pressure is measured?  Ans. Pascal.8. Convert the 5730 K temperatures to the Celsius scale.  Ans 573-273=3000 Celsius.9. What is the physical state of water a 250 C?  Ans Liquid state.10. What produces more severe burns, boiling water or steam and why?Ans Steam as it also has energy of latent heat of vaporization.11. What is the unit of measurement of volume?  Ans cubic metre.12. What are the Characteristics of Particles of Matter?Ans Particles of matter have space between them, particles of matter attract each other and particles of matter are continuously in movement.13. Arrange the following substances in increasing order of forces of attraction between the particles— water, sugar, oxygen?  Ans Oxygen –water –sugar.15. Why should we wear cotton clothes in summer?Ans During summer, we perspire more. And as we know that during evaporation, the particles at the surface of the liquid gain energy from the surroundings or body surface and change into vapour. The heat energy equal to the latent heat of vaporization is absorbed from the body leaving the body cool. Cotton, being a good absorber of water helps in absorbing the sweat and exposing it to the atmosphere for easy evaporation.

Class IX, Chemistry Solved Questions- Chapter 1: Matter in Our Surroundings 1: Which of the following are matter?Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.

Ans: Anything that occupies space and has mass is called matter. Matter can exist in three physical states—solid, liquid, and gaseous. Chair and almond are forms of matter in the solid state.Cold drink is a liquid state of matter.Air and smell of perfume are gaseous states of matter. 

2: Give reasons for the following observation:The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.

Ans: Solids diffuse at a very slow rate. But, if the temperature of the solid is increased, then the rate of diffusion of the solid particles into air increases. This is due to an increase in the kinetic energy of solid particles. Hence, 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.3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?Ans : The ability of a diver to cut through water in a swimming pool shows that matter is made up of particles. and having space between them4. What are the characteristics of particles of matter?Ans: The characteristics of particles of matter are:(i) Particles of matter have spaces between them.(ii) Particles of matter are continuously moving.(iii) Particles of mater attract each other. 

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

Ans: The given substances in the increasing order of their densities can be represented as:Air < Exhaust from chimney < Cotton < Water < Honey < Chalk < Iron

6. 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.

Ans: (a) There is little attraction between particles of gas. Thus, gas particles move freely in all directions. Therefore, 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. Therefore, gas exerts pressure on the walls of the container.(c) A wooden table has a definite shape and volume. It is very rigid and cannot be compressed i.e., it has the characteristics of a solid. Hence, a wooden table should be called a solid.(d) Particles of air have large spaces between them. On the other hand, wood has little space between its particles. Also, it is rigid. For this reason, we can easily move our hands in air, but to do the same through a solid block of wood, we need a karate expert.

7. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.Ans.: The mass per unit volume of a substance is called density (density = mass/volume). As the volume of a substance increases, its density decreases.Though ice is a solid, it has large number of empty spaces between its particles. These spaces are larger as compared to the spaces present between the particles of water. Thus, the volume of ice is greater than that of water. Hence, 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.

8. What is the physical state of water at:(a) 250°C (b) 100°CAns. (a) Water at 250°C exists in gaseous state.(b) At 100°C, water can exist in both liquid and gaseous form. At this temperature, after getting the heat equal to the latent heat of vaporization, water starts changing from liquid state to gaseous state. 

9. For any substance, why does the temperature remain constant during the change of state?Ans. During a change of state, the temperature remains constant. This is because all the heat supplied to increase the temperature is utilised in changing the state by overcoming the forces of attraction between the particles. Therefore, this heat does not contribute in increasing the temperature of the substance.10. What produces more severe burns, boiling water or steam?Ans: Steam has more energy than boiling water. It possesses the additional latent heat of vaporization. Therefore, burns produced by steam are more severe than those produced by boiling water.

11. Why does a desert cooler cool better on a hot dry day?Ans:  In a desert cooler, the water inside it is made to evaporate. This leads to absorption of energy from the surroundings, thereby cooling the surroundings. On a hot dry day, the amount of water vapour present in air is less. Thus, water present inside the desert cooler evaporates more, thereby cooling the surroundings more. That is why a desert cooler cools better on a hot dry day.

12: 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 evaporates. During evaporation, particles of the liquid absorb energy from the surrounding or the surface of the palm to compensate for the loss of energy, making the surroundings cool. Hence, our palm feels cold when we put some acetone or petrol or perfume on it.13. Why are we able to sip hot tea or milk faster from a saucer than a cup?Ans:A liquid has a larger surface area in a saucer than in a cup. Thus, it evaporates faster and cools faster in a saucer than in a cup. For this reason, we are able to sip hot tea or milk faster from a saucer than a cup.14.. What type of clothes should we wear in summers? Ans: We should wear cotton clothes in summers. During summers, we sweat more. On the other hand, cotton is a good absorber of water. Thus, it absorbs sweat from our body and exposes the liquid to the atmosphere, making evaporation faster. During this evaporation, particles on the surface of the liquid gain energy from our body surface, making the body cool.15.Give reason for the following observations.(a) Naphthalene balls disappear with time without leaving any solid.(b) We can get the smell of perfume sitting several metres away. Ans: (a) Naphthalene undergoes sublimation easily i.e., the change of state of naphthalene from solid to gas takes place easily. Thus, naphthalene balls disappear with time without leaving any solid.(b) Gaseous particles possess high speed and large spaces between them. Particles of perfume diffuse into these gaseous particles at a very fast rate and reach our nostrils. This enables us to smell the perfume from a distance.

16. What is the physical state of water at−− (a) 25°C (b) 0°C (c) 100°C 

Ans:  (a) Water at 25°C is present in the liquid state. (b) At 0 °C, water can exist as both solid and liquid. At this temperature, after getting the heat equal to the latent heat of fusion, the solid form of water i.e., ice starts changing into its liquid form i.e., water.(c) At 100 °C, water can exist as both liquid and gas. At this temperature, after getting the heat equal to the latent heat of vaporization, water starts changing from its liquid state to its gaseous state, i.e., water vapors.

17.. 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) At room temperature (25 °C), water is a liquid because it has the following characteristic of liquid:(i) At room temperature, water has no shape but has a fixed volume that is, it occupies the shape of the container in which it is kept.(ii) At room temperature, water flows.(b) An iron almirah is a solid at room temperature (25 °C) because: (i) it has a definite shape and volume like a solid at room temperature.(ii) it is rigid as solid at room temperature.

18. Why is ice at 273 K more effective in cooling than water at the same temperature? Ans: Ice at 273 K has less energy than water (although both are at the same temperature). Water possesses the additional latent heat of fusion. Hence, at 273 K, ice is more effective in cooling than water.

Matter in Our Surroundings Class IX- Chemistry Questions Banks-1Chemistry Adda Class IX, Chemistry Questions BanksChapter 1: Matter in Our Surroundings

1.      What is the normal room temperature? [1] 2.      Are the melting point of the solid state and the freezing point of the liquid state of a substance

different? [1] 3.      A certain substance ‘A’ cannot be compressed but takes up the shape of any container in which

it is placed. What is the physical state of 'A'? [1] 4.      A rubber band changes its shape when stretched. Can it be regarded as solid? [1] 5.      What are volatile liquids? [1] 6.      Which scale of measuring the temperature is the best? [1] 7.      Define diffusion [1] 8.      Is matter continuous or particulate? [1] 9.      What are the factors on which evaporation depends? [1] 10.  Define humidity. [1] 11.  Define evaporation. [1] 12.  Write the full form of L.P.G. & C.N.G. [1] 13.  Why do the states of matter differ? [1] 14.  Define melting point. [1] 15.  Inspite of being solid, a sponge is compressible. Comment. [1] 16.  What are the factors that determine the state of a substance? [2] 17.  Why does our palm feel cold when we put some acetone, petrol or perfume on it? [2] 18.  Liquids generally have lower density as compared to solids. But ice floats on water. Why?[2] 19.  Why do we sweat on a humid day? [2] 20.  Why do solids generally lack the property of diffusion? [2] 21.  How will you demonstrate that air contains water vapour ? [2] 22.  Can matter change its state? State the conditions under which it changes. [2] 23.  Why do we see water droplets on the outer surface of a glass containing ice-cold water? [2] 24.  Explain why there is no rise in temperature of water when it starts boiling although it is still

being heated. [2] 25.  What is dry ice? Why it is known so? [2] 

Chapter 1: Matter in Our Surroundings  Class IX, CBSE TEST PAPER-02    1. 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                     2. 300k will have its corresponding temperature in degree centigrade as:-(a) 300c (b) 3000c (c) 270c (d) 6730c        3. 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 4. Physical state of water at 250c, 00c and 1000c is respectively(a) liquid, solid and gas                                       (b) solid, liquid and gas(c) solid, gas and liquid                                       (d) gas, solid and liquid  5. What happens when the temperature of the solids increase ?6. When heat is being supplied to a solid, then what does the heat energy do to the particles of solid?7. Why is it that on increasing the wind speed the rate of evaporation increases ?8. Why do we say that evaporation is a surface phenomenon?                9. What is the state of inter particle distance inside a solid, liquid and gas?                 10. Why it is that to smell cold food, we have to go close but smell of hot food reaches us several meters away?    11. Why is it that a wooden chair should be called a solid and not a liquid?                    12. Give an experiment to show that ammonium chloride undergoes sublimation.            CBSE TEST PAPER-02 CLASS - IX Science(Matter in our surrounding) [ANSWERS]Ans 01. (c)         Ans 02. (c)         Ans 03. (a)         Ans 04. (a)Ans 05. 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.Ans06. 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.

Ans07. 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.Ans 08. Evaporation is called a surface phenomenon because only particles of the surface of liquid gains energy and changes into vapors.

Ans09. 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.Ans10. 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.Ans11. 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.Ans12. Experiment to show that ammonium chloride (NH4Cl ) undergoes sublimation:-

(a) Take an inverted funnel and inside it china dish with crystal of ammonium chloride (NH4Cl).

(b) Heat the crystals with the help of a burner.

(c) As soon as the crystal is heated, we observe the vapors of NH4Cl and the solidified Ammonium chloride (NH4Cl) 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).

Class IX, Chemistry Questions Paper: Chapter 1: Matter in Our SurroundingsQ1: Convert 570 K into Celsius scale. (1 mark)Q2: What is humidity? (1 mark)Q3: Give reasons:a. The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.b. A diver is able to cut through water in a swimming pool. (2 mark)Q4: Which phenomenon occurs during the following changes? (2 mark)a. Size of naphthalene ball decreases             b. Drying of clothesQ5: Define the following (3 mark)a. Condensation                   b. Latent heat of fusion c. freezingQ6: Explain why gases are easily compressible as compared to liquids and solids. (3 mark)Q7: Why do plants require more leaves during summer? (3 mark)Q8: List any four factors on which evaporation depends? Explain in short any three factors. (5 marks)Solution:Ans 1: Temperature in oC = Temperature in Kelvin -273 (1/2mark)Therefore, Temperature in oC = 570 K -273= 297 oC (1/2 mark)Ans 2: Presence of water vapour in air is called humidity. (1 mark)Ans 3: a. The particles of hot sizzling food have more kinetic energy and thus diffuse rapidly in the air as compared to cold food which possesses less kinetic energy. (1 mark)b. Particles of water contain spaces between them. Hence a diver is easily able to cut through water in a swimming pool (1 mark)Ans 4: a. Sublimation (1 mark)           b. Evaporation (1 mark)Ans 5: a. Condensation: Process in which a gas changes into liquid state by giving out heat at constant temperature is called Condensation. (1 mark)b. Latent heat of fusion: It is the amount of heat energy required to change 1 kg of solid into liquid at its melting point. (1 mark)c. Freezing: Process in which a liquid changes into solid by giving out heat at constant temperature is called Freezing. (1 mark)Ans 6: Gases are easily compressible because they have weak forces of attraction between the molecules and have more intermolecular space. (1 mark)In liquids there is a stronger force of attraction between the molecules and less intermolecular space as compared to gases. Hence, they are not as easily compressible as compared to gases. (1 mark)In solids forces of attraction among molecules is strongest as compared to both liquids and gases. Further intermolecular space is least as compared to liquids and gases. Hence, they are least

compressible as compared to gases and liquids. (1 mark)Ans7: Evaporation of water from leaves of plants is called transpiration. Transpiration helps the plants to keep themselves cool. During summers as the temperature increases more transpiration takes place in order to keep themselves cool. Therefore, more leaves are required for transpiration. Hence, plants acquire more leaves during summer. (3 marks)Ans8: The rate of evaporation depends on following factors:1) Surface area exposed to atmosphere (1/2 mark)         2) Temperature (1/2 mark) 3) Humidity (1/2 mark)                                                   4) Wind speed (1/2 mark)1) Surface area exposed to atmosphere: Since evaporation is a surface phenomenon, therefore, it increases with an increase in surface area. (1 mark)2) Humidity: The air around us cannot hold more than a definite amount of water vapour at a given temperature. If the amount of water in air is already high, the rate of evaporation decreases. So, evaporation decreases with increase in humidity. (1 mark)3) Wind speed: With the increase in wind speed, the particles of water vapour move away with the wind, decreasing the amount of water vapour in the surroundings. This results in a faster rate of evaporation. So, evaporation increases with the increase in wind speed. (1 mark)