Class 9th Science: Chapter 1 Matter in Our Surroundings
States of Matter
Everything in this universe is made up of matter. Matter is defined as any substance that has mass, occupies volume and may be perceived by the senses.
Exception: Phenomena like heat, electricity, light, sound, magnetism, vaccum, shadow are not matter because they have no mass and does not takes up space.
Matter is made up of small particles. The particles of the matter are very small. We cannot see them even with a high power microscope.
The particles of the matter have following characteristics:
- Matter is made up of small particles.
- The particles in the matter have spaces between them. This space is called inter molecular space.
- The particles in the matter are moving in nature, because the particles of a matter have kinetic energy. The motion of the particles increases with an increase in temperature.
- The particles in the matter attract each other, but this mutual force of attraction is effective only when the particles are very close to each other. In solids the particles are closely packed and hence they have greater intermolecular forces attractions while in gases, the particles are loosely held. Hence they have weak forces of attractions.
Diffusion: The intermixing of the particles of two or more substances on their own is called diffusion.
The diffusion is faster in gases. The rate of diffusion is different in different gases. Lighter gas diffuses at faster rate than heavier gases. Diffusion is also takes place in liquids as well as solids. However the rate of diffusion in solids is fairly low. Diffusion in liquids is slower than gases because the particle of liquids moves slowly
Factors effecting diffusion:
Density: Rate of diffusion is inversely proportional to the density of a gas or liquid. Higher the density lesser will be the rate of diffusion.
Temperature: Rate of diffusion is directly proportional to the temperature. As the temperature increase the kinetic energy of the particles increases and they move with greater speed resulting in an increased rate of diffusion.
Classification of matter: On the basis of its state, matter has been classified by the scientists into five states namely - solid, liquid, gas, plasma and Bose-Einstein Condensate. Among these states, the most common states of matter that exists around us are as solids, liquids and gases.
Solid state: When the particles are bound together firmly they form solids. In solids, the particles simply vibrate about their fixed positions, because their kinetic energy is low and not enough to let them break away from their mutual force of attraction. Therefore, solids have definite shapes, volumes and are not compressible. For the same reason they do not flow, or diffuse.
Exceptions: A rubber band can be stretched under force and regains the same shape when the force is removed. If the same rubber band is stretched maximum with excessive force it breaks.
Sponge is another example of solid, which has minute holes in which the air is trapped. When it is pressed with a hand the air is expelled out and it gets compressed.
Liquid state: In liquids, the kinetic energies of the particles are more than in solids, and the particles are not bound to any fixed positions. They move around freely, at random, throughout the liquid. However, they do not have enough kinetic energy to break out of the boundary of the liquid mass. That explains why liquids do not have definite shapes, and flow or diffuse freely, but they do have definite volumes. Also, compared to solids, there are more spaces between the particles of liquids, but not enough to make liquids compressible.
Gaseous state: In gases, the particles are not packed together at all, because their kinetic energies are high enough to let them break away from any boundaries. They are free to move around in random motion. That is why gases have no definite shape or volume, and they flow and diffuse easily. They collide with each other, and with the walls of their container. That’s how a gas exerts pressure on its container. Also, because the spaces between the particles are large, gases are highly compressible.
Volume and shape
Definite shape and volume
Shape of container and definite volume
No definite shape and volume
Cannot be compressed, except porous solids
Cannot be compressed
Can be compressed easily
Particles do not flow
Particles flow easily
Diffuse very fast
Force of attraction between particles
Plasma state: Plasma is the fourth state of matter. Plasma is similar to the gaseous state. The state consists of super energetic and super excited particles in the form of ionized gases. Plasma is made by heating a gas it lose all its electrons .it is present in stars .The plasma is produced in in sun and stars because of very high temperature. The sun and stars glow because of the presence of plasma in them.
The fluorescent tube and neon sign bulbs consist of plasma. The gas present inside these bulbs and tubes is inert gas. When electricity is passed through them the gas gets ionised and charged. This charging up creates a glowing plasma, having a special colour depending on the nature of gas.
Bose-Einstein condensates: The theory of BEC was developed by Indian physicist Satyendra Nath Bose in 1920 was developed the theory of BEC. Later Albert Einstein predicted a new state of matter – the Bose-Einstein Condensate (BEC).
The BEC is formed by cooling a gas of extremely low density. Bose-Einstein condensate refers to the collapse of atoms into a single quantum state. It is found at low temperatures when atoms are not able to move at all.
Interconversion of States of Matter
Matter can change from one form to other form i.e from solids to liquids to gases.
The phenomenon of the change of matter from one state to another and back to original state is known as interconversion of the sates of matter.
Matter can be changed from one state to another by changing temperature or pressure.
Change in state of water: When heat energy is supplied to ice it changes into water and then to vapor. If we cool the steam it gets converted into water and further cooling of water changes into ice.
Here the heat energy is used up in changing the state of matter. the heat is used to increase the kinetic energy of the particles of ice to such an extent that they break away from the rigid lattice structure of the solid form, ice, and move around freely to form the liquid form, water. So, until all the ice has melted, the heat absorbed does not raise the temperature of the ice-water mixture. In the same way the temperature doenot change while a liquid is boiling. This heat, which does not raise the temperature of the body, is called Latent Heat.
Melting or Fusion: Melting is the process where solid changes into a liquid at a particular temperature.
Melting point: The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
Melting points of some solids:
Latent heat: The word 'latent' means hidden. The characteristic amount of energy absorbed or released by a substance during a change in its physical state that occurs without changing its temperature is known as latent heat.
Latent heat of fusion : Latent heat of fusion is the amount of heat energy required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.
Boiling: Boiling is the process where a liquid changes into a vapour at a particular temperature.
Boiling point: Water boils at 1000C. At that temperature, it changes from the liquid state to the gaseous state. The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point
Boiling points of some liquids:
Latent heat of vaporization: Latent heat of vaporization is the amount of heat energy required to change 1 kg of liquid into a gas at atmospheric pressure at the boiling point.
Freezing: The process, where a liquid converts into a solid, is called freezing or solidification.
On cooling a liquid the particles come closer due to the decreased kinetic energy.When the particles come closer the inter particular spaces are reduced and the forces of attractions increased. Finally the particles are arranged themselves in a regular, compact manner.
Evaporation: The process where a liquid changes into vapor at any temperature below its boiling point is evaporation .Evaporation is a surface phenomenon. i.e evaporation takes place at the surface of the liquid.
Factors affecting evaporation:
- Surface area
- Humidity and
- Wind speed.
Rate of evaporation: Surface area
The rate of evaporation increases with an increase of surface area. When the surface area is more, evaporation will be faster.
For example shallow quarries or bunds are built near the sea. The shallow bunds provide a relatively large surface area for water to evaporate quickly, Water from these bunds evaporates, leaving salt behind. Then the salt is collected and refined before use.
Rate of evaporation: Temperature
The rate of evaporation increases with an increase of temperature.
Cloths dry faster on a sunny day than on a cloudy day
Rate of evaporation: Effect of Humidity
The rate of evaporation increases with decrease in humidity.
Rate of evaporation: Effect of Wind
The rate of evaporation increases with an increase in wind speed.
The water vapour particles in atmosphere move away with the winds. This results in a decrease of the amount of water vapour in the surroundings. Due to this reason, clothes dry faster on a windy day than a normal day.
Evaporation cause cooling:
During the process of evaporation, the particles of liquid absorb energy from the surroundings, to regain energy lost during evaporation. This absorption of energy from the surroundings makes the surroundings cold.
Differences between boiling and evaporation:
It is a rapid process.
It is a slow process.
It is takes place at the entire mass of the liquid.
It takes place at the surface of the liquid.
It takes place at any temperature.
It takes place at specific temperature called the boiling point of the liquid.
It causes cooling i.e the substance becomes cool due to evaporation.
The temperature of the liquid remains constant during boiling process.
Condensation: The process where vapor changes to a liquid is called condensation.
Example: The water vapour condenses and we receive the same water in the form of rain.
When you pour cold water in a glass. You will observe the formation of water droplets on the outer surface of the glass . This is due to the condensation of water vapour present in atmosphere.
Sublimation: The process, where a solid, on heating, directly changes into gas without changing into liquid, and a gas, on cooling, directly changes to solid without changing into liquid is called sublimation.
Example: Solid ammonium chloride, on heating directly converts into vapors without changing to the liquid state. These vapors get condensed to the solid state by condensation process.
The sublimation of Naphthalene and camphor can take place without heating them. They sublimes at room temperature.
Difference between sublimation and vaporization: Vaporization is a transitional phase of matter from a solid or liquid phase to a gaseous phase.
For example: When heat energy is supplied to ice it changes into water and then to vapor.
Sublimation is a transitional phase of matter from a solid phase to gaseous phase without changing into a liquid phase.
For example: Solid ammonium chloride, on heating directly converts into vapors without changing to the liquid state.
Liquification process: A gas is liquefied by applying high pressure and reducing the temperature.
Example: petroleum gas is liquefied by applying high pressure and reducing the temperature to liquefied petroleum gas (LPG).
This principle is used in the liquification of air to separate the components of air.
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