Matter In Our Surroundings Class 9 Cbse Science Subject English Medium

Matter in our surroundings

Matter
Matter is anything that has mass and volume which occupies space and can be felt by one of our sense organs is called matter

SI unit of mass is kg
SI unit of volume is Cubic metre, a common unit for measuring volume is litre.

Classification of matter
1. Earlier Indian philosophers classified matter in to five basic elements called Panch tatva, they are air water Earth sky and fire
According to Indian philosophers every living or nonliving was made up of these five basic elements
2. Now matter is also classified into groups according to their physical properties and chemical nature
That is solid, liquid and gas- based on the particle arrangement of their physical property
For elements, compounds and mixtures – based on chemical nature

Physical nature of matter

When we study the physical composition of matter we find
1. Every matter is made up of particles which different shape, size and nature from different types of matter
2. Particles of matter are very small or tiny, which is beyond human vision

Characteristics of particles of matter

Important characteristics of particles of matter are:
1. Particles of matter have space between them
2. Particles of matter are in a state of continuous movement, which proves that they possess some form of energy which is called Kinetic energy. As temperature rises kinetic energy of particles increases and hence the particles move faster
3. The particles of matter have a nature to defuse that is they intermix on their own with each other. They do it by getting into the spaces between the particles, when there is an intermixing of particles of two different types of matter it is called diffusion
3. Particles of matter attract each other and the force of attraction exists between the particles which are known as the intermolecular force of attraction. This force holds the particles together and the strength of the force of attraction varies from every matter to another

States of matter
Matter around us exists in three different states which are is liquid, solid and gas. The state of matters occur due to the variation in the characteristics of the particles of matter

Solid-state
Solid-state is defined as a form of matter which possesses rigidity, is incompressible and has a definite shape and definite volume

Characters and properties of solid-state are:
1. Are solids have a definite shape, district boundaries and fixed volumes that is they have very low compressibility. This means that you cannot compress a solid easily using pressure
2. Solids have a tendency to maintain their shape when an outside force is applied
3. Solids do not diffuse generally or diffuse at a very slow rate
4. Solids may break under force but it is difficult to change their shape because they are rigid
5. Solids have a higher density compared to liquid or gas matter

Examples of solid are: Sand, wood, gold silver metal

Liquid state
The liquid is defined as a form of matter which possesses fixed volume but doesn’t have a fixed shape

Some properties of liquid state are:
1. Liquids do not have a definite shape that means they can take shape of the container in which they are kept
2. Liquids flow and change their shape hence they are not rigid and can be called fluid
3. Solids, liquids and gases can diffuse into liquid, the gases from the atmosphere diffuse and dissolve in water which helps organisms and animals living and water to survive. For example, Oxygen and Carbon dioxide diffuses in water from the atmosphere in a gaseous form which helps animals breathe underwater
4. Liquids are almost incompressible
5. The attraction force between particles in a liquid is less than solids but greater than gas
6. The rate of diffusion of liquids is higher than that of solids due to the fact that in liquid state particles move freely and have greater space between each other compared to solid-state particles
7. Density of liquid is less than compared to solid matter. There are some exceptions for example ice has less density compared to water hence you will see ice cubes will float on the water surface

Gaseous state
Gas can be defined as that form of matter which possesses high compressibility and does not have any definite shape or volume

Some important properties and characters of gas are:
1. Gases have a tendency to flow like liquids and therefore there are also called fluids
2. Gases show the property of diffusing very fast into Each Other due to the high speed of particles and large spaces between them. The speed of diffusion is much higher compared to liquid matter
3. Gases are highly compressible for example oxygen tanks and liquefied petroleum tanks are filled with compressed gases which are used for day to day activities
4. In the gaseous state the particles move about at random direction at high speed which creates random movement and creates pressure on the walls of the container within which it is kept
5. Density of gaseous matter is very low and has a low weight compared to liquid or solid

Change of States of matter
In our daily life you will discover that various substances exist in three states that is solid, liquid and gas what is the most common example which exists in three states

Ice – solid state
Water – liquid state
Water vapour- gaseous state

Interconversion of States of matter
The states of matter are interconvertible. The process or phenomenon of change of matter from one state to another and back to its original state by altering the conditions like a change of temperature and pressure is called interconversion of states of matter

The two factors make it possible for conversion from one state to another:
1. Change in temperature
2. Change in pressure

Terms involved in change of state
Following terms are used in change of state:
1. fusion or melting and melting point
The process of conversion of matter from which solid state to its liquid state at a specific condition of temperature and pressure is called fusion or melting. The Definite temperature at which a solid starts to melt is called its melting point of that solid. For example building point of ice is zero degree centigrade or 273.16 k, please do keep in mind the higher the melting point of a substance the greater will be the force of attraction between its particles

2. Boiling and boiling point
The process of conversion of a matter from its liquid state to gaseous state at a specific condition of temperature and pressure is called boiling
It is a bulk phenomenon and the temperature at which the liquid starts to boil at atmospheric pressure is known as its boiling point

3. Sublimation
This is a process of change of solid state directly into state without passing through the liquid state upon heating and vice versa on cooling and this process is known as sublimation
Many solids change their state from solid to gas such as naphthalene, camphor, iodine

4. Vaporization
This is a process of conversion of liquid state to gaseous state at a specific condition of temperature and pressure and this process is called vaporization

5. Freezing and freezing point
The process of conversion of matter from its liquid state to solid state at a specific temperature and pressure is called freezing.
It is the reverse process of fusion or melting and The Definite temperature at which liquid changes into solid state by giving out energy as heat at 1 atmospheric pressure or 1 ATM is called freezing point

6. Condensation
The process of conversion of matter from its gaseous state to liquid state at specific temperature and pressure is called condensation. It is the reverse process of vaporization

Effect of change of temperature

When a solid is heated, kinetic energy of which particles increases due to this increase of kinetic energy the particles start vibrating with greater speed
The energy supplied by the heat exceeds the forces of attraction between the particles
Then the particles leave their position and started moving more freely and randomly at a certain stage that is melting point solid melts and converts into liquid state

At a specific temperature a point is reached when the particles have enough energy to break free from their forces of attraction to each other at this temperature that is boiling point the liquid starts to change its shape from liquid to gas
And by decreasing the temperature or by cooling a gas can be converted into liquid state and a liquid can be converted into a solid state

This is effect of change of temperature on the physical state may be summarised as

Solid state – when heated becomes – liquid
Liquid state – when heated becomes – gas

Gas – when cooled becomes – liquid
Liquid – when cooled becomes – solid

Is it can be concluded that state of matter can be changed into another by changing the temperature

Scales of measuring temperature

There are three scales of measuring temperature which are as follows:
1. Temperature on Kelvin scale

Temperature [on Kelvin scale] = Temperature on Celsius scale + 273.16

For convenience we take, zero degree centigrade= 273K

2. Temperature on Celsius scale

Temperature [on Celsius scale] = Temperature on Kelvin scale + 273.16

3. Temperature on fahrenheit scale

Celsius and Fahrenheit temperatures are related to each other by the relation;

C = 5/9 x (F – 32)

Latent heat
When heat is given to a substance its temperature increases. However when heat is supplied to change the physical state of a substance there is no increase in temperature of the substance and no change in the state of the the matter.
Hence the heat energy which has to be supplied to change the state of the substance is called latent heat

The meaning of the word latent is hidden, latent heat does not raise the temperature but latent heat is always supplied to change the state of a substance

There are two types of latent heat:
1. Latent heat of fusion – which helps to convert solid into liquid
The amount of heat energy required to change 1 kg of solid into liquid at atmospheric pressure and its melting point is known as latent heat of fusion

2. Latent heat of vaporization – which helps convert liquid to gas
The amount of heat energy required to convert 1 kg of liquid into gas at its boiling point without any rise in temperature is known as latent heat of vaporization

Effect of change of pressure

The physical state of a substance or matter can be changed by changing the pressure
Increase in pressure brings particle together and increases the force of attraction between them which brings the change that is when high pressure is applied to a gas its temperature is reduced the gas is converted into liquid that is the gas changes its shape to liquefied form

The pressure exerted by gas is measured in atmospheric (atm) unit.

The pressure of air in atmosphere is called atmospheric pressure

Atmospheric pressure at sea level is taken as one ATM which is also normal atmospheric pressure, as we go higher in altitude the atmospheric pressure decreases

Pessure of 1 Atm = 1.013 x 10 5 Pa.

Evaporation

The process of conversion of liquid into its vapour state at any temperature below its boiling point is called evaporation
The particles of a liquid have different amount of kinetic energies and the particles present at the surface of a liquid have comparatively high kinetic energy as compared to those present in bulk

Hence particles at the surface with high kinetic energy is able to break away from the forces of attraction between other particles and converts into paper

You are wet clothes become dry because of this reason

Factors affecting evaporation
1. Surface area
Evaporation is a surface phenomenon that is that means it occurs on the surface of a liquid hence when the surface area is increased the rate of evaporation also increases

2. Temperature
The rate of evaporation of a liquid increases with the rise in temperature with increase in temperature more number of particles Get Enough kinetic energy to transform themselves into vapour state that’s why high temperature results in higher evaporation

3. Humidity
Humidity is the amount of water vapour available in the atmosphere, our atmosphere can hold certain amount of water beyond which it can not observe any water through evaporation
If the amount of water is higher we called at Higher humidity and then evaporation rate is very low and it’s the opposite when the amount of water vapour in the air that is humidity is low then evaporation will be much higher

4. Wind speed
With increase in wind speed the particles of water vapour move away quickly with the wind decreasing the amount of water in the surrounding which reduces humidity that is the reason why high wind speed causes more evaporation

The liquids which evaporate faster are called volatile liquids

Evaporation causes cooling effect
If you keep open vessel the liquids keep on evaporating the reason because the surface area absorbs the energy and hence the surface particles evaporate in the air which reduces the energy e in the liquid and keeps it cool this absorption of energy from the surrounding makes the surrounding called

Some daily life examples of the cooling effect of evaporation are given:
1. When Ice cold water is kept in a glass tumbler for some time water droplets are observed on its outer surface

This happens because the water vapour present in the air come in contact with the glass tumbler which is cooled by the the Ice cold water and then it loses its heat and condenses to form small water droplets. This formation of droplets of water on the outside surface confirms that water vapour is present in the air

2. Cotton clothes are used to wear during summer season
Cotton is a very good absorber of water so it helps absorb sweat from our body hence wearing cotton clothes helps in easy evaporation of sweat from human body and when this sweat evaporates it takes the latent heat of the the vaporization from our body which in turn cools the body hence the person feels comfortable

3. People Sprinkle water on their roof top or open ground on hot sunny day

When water is sprinkled on a hot surface it gets evaporated by absorbing the heat energy available on the surface and when the water evaporates it takes away the heat energy which reduces the temperature of the surface and hence making it cool

4. Liquids like acetone and alcohol placed on our skin provides a cooling effect

Acetone and alcohol are volatile liquids and when it is rubbed on our skin in IT gains energy and takes away the heat from ours body and evaporates which gives a gives us a feeling of cooling

Plasma and Bose Einstein condensate – two more States of matter

Plasma
This state of matter consists of super energetic and super excited particles these particles are in the form of ionized gases

Formation of Plasma
In light bulbs for fluorescent lights there is helium gas
The gas gets ionised when electric current or electric energy is flowing through it and it charges up creating plasma glowing inside the bulb or tube
The plasma glows with special colour depending on the nature of gas present

The sun and the stars glow because of the presence of Plasma in them

Bose-Einstein condensate

In 1920 Indian Bengali physicist Satyendra Nath Bose had done some calculations for the fifth state of Matter based on is calculation Albert Einstein predicted a new state of matter which is called Bose-Einstein condensate

Bose-Einstein condensate is formed by cooling a gas of extremely low density about one hundred thousand the density of normal air to super low temperature

What you have learnt

• Matter is made up of small particles.
• The matter around us exists in three states— solid, liquid and gas.
• The forces of attraction between the particles are maximum in solids, intermediate in liquids and minimum in gases.
• The spaces in between the constituent particles and kinetic energy of the particles are minimum in the case of solids, intermediate in liquids and maximum in gases.
• The arrangement of particles is most ordered in the case of solids, in the case of liquids layers of particles can slip and slide over each other while for gases, there is no order, particles just move about randomly.
• The states of matter are inter-convertible. The state of matter can be changed by changing temperature or pressure.
• Sublimation is the change of solid state directly to the gaseous state without going through the liquid state.
• Deposition is the change of gaseous state directly to solid state without going through the liquid state.
• Boiling is a bulk phenomenon. Particles from the bulk (whole) of the liquid change into a vapour state.
• Evaporation is a surface phenomenon. Particles from the surface gain enough energy to overcome the forces of attraction present in the liquid and change into the vapour state.
• The rate of evaporation depends upon the surface area exposed to the atmosphere, the temperature, the humidity and the wind speed.
• Evaporation causes cooling. • 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.
• Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at its melting point.

Some measurable quantities and their units to remember: