MATTER IN OUR SURROUNDINGS

IMPORTANT TERMS

Matter: - Anything that occupies space and have mass is called matter.

Diffusion: -The process of intermixing of particles of two or more substances on their own is called diffusion.

Density: - The mass per unit volume of a substance is called density. Its unit are kg/cubic cm.

Pressure: - Pressure is defined as force per unit area. Its unit are Pascal.

Melting Point: - The temperature at which solid changes into liquid completely is called melting point.

Melting: - The process in which solid changes into liquid is called melting. It is also called fusion.

Boiling: - The process of converting liquid into vapours is called boiling.

Latent heat of vapourisation: - The amount of energy required to change 1 kg of liquid into vapours at atmospheric pressure without any change in temperature.

Vapourisation: - It is a process in which liquid changes into vapours.

Sublimation: - It is a process in which solid directly changes into vapours without changing into liquid state. Examples- camphor, iodine, naphthalene.

Kinetic Energy: - It is the energy possessed by the particle by virtue of its motion.

Atmosphere(atm): - It is a unit of measuring pressure exerted by gas. The pressure of air in atmosphere is called atmospheric pressure.

Pascal(pa): - It is the SI unit of pressure. 1 atm = 1.01 x 10 raise to power 5

Plasma: - It is the fourth state of matter. It consists of super energetic and super excited particles in the form of ionized gas.

Bose-Einstein Condensate: - It is the fifth state of matter which is formed from the matter which is formed from the matter that has been cooled to near absolute zero.

 

Physical Nature of Matter

1. Matter is made up of particles - Matter is made up of small particles and there is space between particles of matter. When we dissolve sugar or salt in water, it gets entered into the space between water molecules, therefore, the level of water does not change.
2. Size of particles of matter – The particles of matter are extremely small in size which cannot be even seen with microscope. For example just a few crystal of potassium permanganate can colour a large volume of water. So there are million of tiny particles in just one crystal of potassium permanganate.

Characteristics of Particles of Matter

1. Particles of matter have space between them – When we dissolve sugar, salt or potassium permanganate in water, particles get evenly distributed in water. Particles of one type of matter diffuse into the space between particles of the other.
2. Particles of matter are continuously moving – Particles of matter are continuously moving, they posses kinetic energy which increase with increase in temperature.
3. Particles of matter attract each other – Particles of matter have force acting between them, these forces keeps the particles together. The strength of this force of attraction varies from one kind of matter to another.

 

States of Matter

Matter can be classified on the basis of its physical state i.e. Solid, Liquid and Gas

• The Solid State

1. Solids are the state of matter which have definite shape, distinct boundaries and fixed volume.
2. Solids have negligible compressibility. Solids have tendency to maintain their shape when subjected to outside force.
3. Solids may break under force but it is difficult to change their shape. They are so rigid.
4. Solids have high density as compared to other states of matter.
5. The kinetic energy of particles in solids is very less. They only vibrate about their mean position.
6. Diffusion in solids is negligible.
7. Solids cannot flow, Solids do not have property of fluidity.
8. The intermolecular forces of attraction are stronger in solids as compared to other state of matter.

 

• The Liquid State

1. Liquids are the state of matter which do not have fixed shape but have fixed volume.
2. They have low compressibility but more than solids.
3. They have lower density as compared to solids.
4. The intermolecular forces of attraction are weaker as compared to solids.
5. The particles of liquid have more kinetic energy than particles of solids hence are free to move.
6. The particles of liquids show diffusion and can show the property of intermixing.

• The Gaseous State

1. Gases do not have fixed volume and fixed shape, they take the shape of the container.
2. Gases can flow in any directions hence show fluidity.
3. Gases are highly compressible.
4. Gases have lower densities as compared to solids and liquids.
5. Particles of gas have high kinetic energy as compared to particles of liquid and solids.
6. Rate of diffusion is fastest in gases.
7. Particles of gas have weak intermolecular forces of attraction due to large distance of separation between the particles.

Change of State

The state of substance depends on the temperature and pressure. For example water exists as solid at 0 degree celsius, as liquid at room temperature whereas in gaseous state at 100 degree Celsius.

Effect of Change of Temperature

On increasing the temperature of solids, the kinetic energy of the particles increases. Due to increase in kinetic energy, particles starts vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the particles. The particles leave their fixed positions and starts moving freely. A stage is reached when solid starts melting to become a liquid at atmospheric pressure is called its Melting point.

Melting Point of a solid is an indication of the strength of the force of attraction between the particles.

The melting point of ice is 273.16 K or 0 degree Celsius. The process of melting, change of solid into liquid state is known as fusion. Temperature in Kelvin = Temperature in Celsius + 273. Kelvin is the SI unit of temperature, 0 degree Celsius = 273.15 K

 

Latent Heat of Fusion- It is the amount of heat required to change 1 Kg of a solid substance into liquid at atmospheric pressure without any change in temperature at its melting point is called latent Heat of Fusion.

There are some substance which change their state from solid to gaseous directly without converting into liquid state. For Example- Camphor, Naphthalene and Ammonium Chloride etc. A change of state directly from solid to gaseous without changing into liquid or vice versa is called Sublimation.

Effect of Change of Pressure

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

Solid Carbon dioxide is stored under high pressure, solid carbon dioxide gets directly converted into gaseous state on decreasing the pressure to 1 atmosphere without coming into liquid state. This is the reason, solid carbon dioxide is known as Dry Ice.

Liquefication of Gases- Gases can be liquefied at low temperature and high pressure e.g. hydrogen, nitrogen and oxygen can be liquefied at low temperature and high pressure.

Boiling Point- The temperature at which a liquid changes into gas or vapour is known as boiling point. It also indicates the strength of intermolecular forces of attraction. Greater the forces of attraction, higher will be its boiling point. The boiling point of water is 100 Degree Celsius or 373 Kelvin. Boiling is the bulk phenomenon, whole particles from the bulk of the liquid boils and change into vapour state.

Evaporation

We know that particles of matter are always moving and are never at rest. In the case of liquids, a small fraction of particles at the surface, having higher kinetic energy, is able to break away the forces of attraction of all the particles and gets converted into vapours. That is why evaporation is also known as Surface phenomenon. This phenomenon of change of a liquid into vapours at any temperature below its boiling point is called Evaporation.

Factors Affecting Evaporation

1. Surface Area- We know that evaporation is a surface phenomenon. If the surface area is increased, the rate of evaporation also increases. For example- clothes dry faster when we spread them.
2. Temperature- The rate of evaporation increases with the increase of temperature, as more number of particles get enough kinetic energy to go into vapour state.
3. Humidity- Humidity is the amount of water vapour present in the air. The air around us cannot hold more than a definite amount of water vapour at a given temperature. If the amount is already high, the rate of evaporation decreases.
4. Wind Seed- The rate of evaporation increases with the increase in wind speed. For example clothes on the windy day dry faster.

Effects of Evaporation

If a liquid is kept in open vessel, the particles of liquid gets energy from the surroundings to regain the energy lost during evaporation and hence make the surrounding cool. Hence evaporation cause cooling effect.

For example when we put some nail polish remover on the palm, the particles gain energy from the palm or the surroundings and evaporate and cause the cooling effect to the palm.

Latent Heat of Vapourisation- The amount of energy required to change 1 kg of liquid into vapours at atmospheric pressure without any change in temperature at its boiling point is called latent heat of vapourisation.

What is the purpose of wearing cotton clothes in summer

During summer, we perspire more because of 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 and change into vapour. The heat energy equal to latent heat of vapourisation 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.

Plasma- Plasma is the fourth state of matter which consists of super energetic and super excited particles. These particles are in the form of ionized gases. The fluorescent bulbs and neon sign bulbs consists of plasma. In the neon sign bulb there is a neon gas and inside a fluorescent bulb there is helium gas or some other gas. The gas gets ionized and gets charged when electric current flow through it. This charging makes the plasma to glow inside the tube.

Bose-Einstein Condensate- Indian physicist, Satyendra Nath Bose had done some calculations for the fifth state of the matter, further Albert Einstein predicted a new state of matter known as Bose-Einstein Condensate (BEC) which is formed from the matter that has been cooled to near absolute zero(-273 degree Celsius). When a group of atoms cooled to a very low temperature, the velocity decreases because they have very low energies.

Some Interesting Facts

• Unlike other substances, water expands on freezing. This is due to strange shape of water molecule and because of hydrogen and oxygen, water molecule is an open structure with lot of space.
• At temperature 2.17K, just near to absolute zero, part of helium become superfluid and can climbs on the wall.
• If we put a handful of salt into a glass of water, the level of water goes down because the solvent molecules becomes more ordered due to presence of ionized ions.
• A new state of matter is dicovered known as Jahn-Teller Metal, these metals have properties of insulator as well as superconductors.