1. Matter in Our Surroundings Science class 9 exercise page 4
1. Matter in Our Surroundings Science class 9 exercise page 4 ncert book solution in english-medium
NCERT Books Subjects for class 9th Hindi Medium
Introduction of matter
1. Matter in Our Surroundings
(Science-IX)
Matters: Those all objects have mass and occupy space called matters.
- Matter is made up of tiny particles.
- The particles of matter are too much small that we can not imagine. Example - some small particles or crystals of potassium permanganate make a glass of water colourful to add in. one crystal of potassium permanganate, which keep on dividing themselves into smaller and smaller particles. Imagine that how small the particles of matter are ? Which occupy each particles of water in the glass.
The characteristics of the particles of matter:
(i) Particles of matter have space between them.
(ii) Particles of matter are continuously moving.
(iii) Particles of matter attract each other.
(i) Particles of matter have space between them: How matters like salt, sugar, dettol or potassium permangante intermixes with the particles of water easily? This happens due to enough space between the particles of matter. This is the reason that a diver can able to cut through water in the swimming pool.
(ii) Particles of matter are continuously moving : The particles of matter move continuously, so they possess kinetic energy. On increasing temperature the kinetic energy also increases and particle moves faster.
(iii) Particles of matter attract each other : There is a force acting between particles of matter. This force keeps particles together. The strength of this force
of attraction varies from one kind of matter to another.
Solids have greater attraction force than liquid and gas, while gases have less attraction force. This is the reason that gases spread and solids joins strictly together.
The states of matters:
There are three states of matters:
(i) Solid
(ii) Liquid
(iii) Gas
Formation of states of a matter:
These states of matter arise due to the variation in the characteristics of the particles of matter.
- Increasing in space amongs particles causes decreasing in attraction force. This less attraction causes changing in states.
Properties of Solid:
(i) Solid have a definite shape.
(ii) Solid have a fixed volume.
(iii) It cannot be changed its shape.
(iv) Inter molecular force are strongest in solid.
Properties of Liquid;
(i) Liquids have no fixed shape.
(ii) Liquids flow and change shape so they are not rigid.
(iii) They are not compressed.
(iv) Inter molecular force are less strong in liquids.
Properties of Gas:
(i) Gases neither have a definite.
(ii) They can do compressed.
(iii) Gas can also flow.
(iv) Inter molecular force are large space than solid and liquid.
Changing States of Matter
1. Matter in Our Surrounding
Diffusion: Intermixing of particles of two different types of matter on their own is called diffusion.
Why diffusion takes place?
Diffusion is proccess in which particles of matter get intermixed on their own, this happens due to enterance of particles into the spaces.
Solids, liquids and gases these states of matter arise due to the variation in the characteristics of the particles of matter.
Diffusion in Liquids: Solids gases and liquids can diffuse into liquids. The rate of diffusion is higher in liquids 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.
Diffusion of gases in liquids : The aquatic animals can breathe under water due to the presence of dissolved oxygen in water.
Diffusion In Gases : gases are highly compressible as compared to solids and
liquids. In gasious states particles have very less attraction force and larger space between them as compared to other states. Due to this faster movement and having larger space the process of diffusion take place very fast.
Gases exerted pressure on the wall of containner: 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. The pressure exerted by the gas is because of this force exerted by gas particles per unit area on the walls of the container.
The Changing in states of matter:
There are following reasons to change in states of matter:
- Increasing and decreasing in space between particles can be changed in states.
- If increasing and decreasing in movement of particles can be changed in states.
- if the attraction force between particles is increased or decreased then states of matter can be changed.
Above all points indicate that the changing in states is due to change in differents charactristics of matter.
These are following physical quantities that can change the states of matters.
Physical factors which changes the states:
(i) Temperature
(ii) Pressure
TEMPERATURE
1. 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 converted to a liquid.
So the state of matter can be changed into another state by changing
the temperature.
The S.I unit of Temperature is Kelvin (K).
But there are also other units which are used to measure the temperature. These are Celsius (०C) and Fahrenheit (०F).
We can also convert the Kelvin into Celsius and Celsius into Kelvin. And also can convert Celcius to Fahrenheit and so on.
0० C = 273 K
To change a temperature on the Kelvin scale to the Celsius scale you have to subtract 273 from the given temperature, and to convert a temperature on the
Celsius scale to the Kelvin scale you have to add 273 to the given temperature.
For Example converting Celsius to Kelvin We have to add 273 into Celcius Value:
15० C = 15 + 273 K = 288 K
Similarily converting Kelvin into Celsius We have to substract 273 from given Kelvin value.
293K = 293 - 273 ० C = 20० C
The physical states of water on various temperature:
| States | Temperature | Name of matter |
| solid | 0 oC | Ice |
| Liquid | 25 oC | Water |
| Gas | 100 oC | Water-vapour |
Melting Point: The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
Note:- The different materials have different melting point.
Example: The melting point of Ice is 0 ०C.
Boiling Point: The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point.
Note:- The different materials have different boiling point.
Example: The boiling point of Ice is 100 ०C.
SI unit of temperature is Kelven(K).
Changing temperature Scale:
Kelvin to celsius scale:
Converting kelving scale into kelvin, It is 273 is substracted from kelvin value to get celsius temperature.
And 273 is added to get kelvin temperature.
Example:
(i) Convert 320 K into celsius scale
Solution:
320 K = 320 - 273 ०C
= 47 ०C
Celsius to Calvin.
(ii) Convert 25 ०C into kelvin scale
Solution:
25 ०C = 25 + 273 K
= 298 K
Latent heat:
During process of melting, the temperature of the system does not change after the melting point is reached, till the any solid does not melt completely. This heat gets used up in changing the state by overcoming the forces of attraction between the particles. As this heat energy is absorbed by solid without showing any rise in temperature. This hidden temperature is known as latent heat.
Latent heat of fusion:
The amount of heat energy that is required to change 1 kg of a solid into
liquid at atmospheric pressure at its melting point is known as the latent heat of fusion.
So, particles in water at 00 C (273 K) have more energy as compared to particles in ice at the same temperature.
Latent heat of vaporisation:
Latent heat of vaporisation is the heat energy required to change 1 kg of a liquid to gas at atmospheric pressure at its boiling point.
PRESSURE:
2. Pressure : We know that increasing or decreasing space between particles of matter can change its state. if we have to change states of matter, pressure does the same work. Similarily increasing or decreasing pressure causes change in states. Example: Very large quantity of gases is filled in a small cylinder by compression (pressure) to change it in liquid form.
Temperature and pressure is responsible to change the states of matter.
Dry Ice:
Solid 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.
- Solid carbon dioxide is known as dry ice.
Exerting pressure on CO2 gas It convert into Solid CO2 .
Evaporation
Terms for changing states:
(A) Fusion: The process of melting, that is, change of solid state into liquid state is known as fusion.
(B) Solidification: The process of changing liquid state into solid is called solidification.
(C) Vaporisation: The process of changing liquid state into gas is called vaporisation.
(D) Condensation: When gases get converted their state into liquid form is known as condensation.
(E) Sublimation: Sublimation is the change of gaseous state directly to solid state without going through liquid state, and vice versa.
- Phenomenon of changing of a liquid into vapours at any temperature below its boiling point is called evaporation.
- Humidity is the amount of water vapour present in air.
atmosphere (atm) is a unit of measuring pressure exerted by a gas. The unit of pressure is Pascal (Pa):
1 atmosphere = 1.01 × 105 Pa. The pressure of air in atmosphere is called atmospheric pressure.
The atmospheric pressure at sea level is 1 atmosphere, and is taken as the normal atmospheric pressure.
Evaporation:
Phenomenon of changing of a liquid into vapours at any temperature below its boiling point is called 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.
How a liquid get converted into Vapour or get vapourised:
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.
The Factors which influence the rate of Evaporation:
1. An increase of surface area
2. An increase of temperature
3. A decrtrease in humadity
4. An increase in wind speed
1. 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.
2. An increase of temperature: With the increase of temperature, more
number of particles get enough kinetic energy to go into the vapour state.
3. 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.
4. 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.
Understand this main point during evaporation:
In every evaporation 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.
Same fiction can apply for when we pour some acetone (nail polish) or petrol on our palm.
Q:- Why does our palm feel cold when we put some acetone or petrol or perfume on it?
- The particles of acetone or petrol gain energy from your palm or surroundings and get evaporated and this evaporate absorbation of heats from palm causeing the palm to feel cool.
Q: Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
- A saucer increases the surface area for tea or milk cause faster evaporation, this evaporation causing coolness so we able to sip easily.
Q: 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.
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