Matter in Our Surroundings - Revision Notes

What is Matter?
Air, water, stones, sand, clouds, pencils, books – Everything is made up
of matter. Matter is everything in this universe that occupies space and
has mass.
Constituents of Matter
According to the early Indian philosophers, every living and non-living
thing is made of five basic elements called
the Panchtatava – Air, Water, Earth, Sky, and Fire. Therefore, matter is a
composition of these five constituents.
Physical Nature of Matter
Is matter continuous or particulate?
Matter is particulate in nature. This means that matter consists of
particles as you can see in the microscopic image of a cube above.
For Example, If we put a drop of red color in water the color of the water
turns red. This happens because the particles of red color mix with the
particles of water.
What is the size of these particles?
The size of the particles of matter is very small.
They can be broken into further particles as well. For Example, On
dilution of a colorful solution, as shown in the figure below, we can still
see the color. This means there are millions of particles present in the
color which just divide themselves on dilution.
Which of these is matter – happiness, air, sandwich, thoughts, juice, and
eraser? Air, sandwich, juice, and eraser as they have mass, they occupy
space and can be broken into further particles.
Characteristics of Particles of Matter
Particles of matter have three characteristics:
1. Particles of matter have spaces between them
2. Particles of matter are moving all the time
3. Particles of matter attract each other
Particles of Matter have spaces between them
Have you ever wondered what causes salt to get dissolved in water?
Salt gets dissolved in water because their particles have spaces between
them. The particles of the salt get in between the spaces between the
particles of water and a mixture is formed.
We cannot see these particles through naked eyes.
Particles of Matter are continuously moving
Particles are continuously moving
Particles of matter are in motion all the time. Hence, they possess kinetic
energy.
Kinetic Energy – Energy due to motion
The particles of a matter intermix on their own with other particles of a
matter. For Example, Salt in water, Various gases in the air, Ink in water.
Diffusion – The process of mixing two different types of particles together
is called diffusion. Diffusion becomes faster on heating.
The kinetic energy of particles also increases on heating.
Particles of Matter attract each other
The particles of matter are always held together because of a force of
attraction between them.
The amount of this force between the particles varies in different forms
of matter, as shown in the figure below:
Solids have the highest force of attraction. That is why we cannot move
our hands through a solid object. The particles are so tightly bound.
Similarly, particles of gases have the least force of attraction in them. We
can move our hands easily in the air, can’t we? This is because the
particles of air are loosely bound.
We can arrange the force of attraction between different types of matter
(solids, liquids, and gases) in increasing order as:
We can also move our hands through water or liquid matter but not as
freely as we can in the air. This means that they are also loosely bound to
some extent.
Gas < Liquid < Solids
States of Matter
Now we know that particles of matter have a force of attraction between
them. Based on this criterion, we can say that matter is present in three
different states: solid state, liquid state, and gaseous state.
The Solid State
Solids are the objects that have these three properties:
They have a specific shape.
They have distinct boundaries.
They have a volume.
There is less kinetic energy among the particles in solids. They are
generally arranged in an order. Thus they possess a fixed shape. They
cannot be compressed.
The force of attraction is the maximum among the particles of solids.
There is not much space between the particles. Therefore, they cannot be
compressed.
Which of these are solids: Rubber band, Sponge, Salt?
All of them are solids. All of these follow the properties of solids. A
rubber band and sponge change their shape only when we apply force on
to them. It might appear to you as if salt is taking the shape of the
container in which you put it but actually each of its grain has its own
definite shape.
The Liquid State
Liquids have the following properties:
Liquids have a fixed volume
Liquids do not have a fixed shape.
The force of attraction in liquid particles is less than solids. Therefore,
there is a space between the particles of liquids and they can flow easily.
They cannot be compressed. That is why they are also called fluids.
Particles of liquids arrange each other is not fixed. You might have seen
that liquids take the shape of the container in which we put them. This is
because the particles of liquids have a high kinetic energy, they always
keep on moving.
Can other matter diffuse into liquids?
Yes, other matter can diffuse into liquids whether it is solids, liquids, or
gases. This is so because there is a space between the particles of liquid
so particles of other matter can slip into those spaces.
Diffusing solids into liquids: Mixing sugar in tea
Diffusing liquids into liquids: Mixing ink in water
Diffusing gases into liquids: The presence of oxygen and carbon dioxide
in water
The Gaseous State
Gases have the following properties:
They do not have a fixed volume.
 They do not have a fixed shape.
The particles of gases have the least or almost no force of attraction
between them. Therefore, the particles have a large number of spaces
between them and they can freely move in any direction.
Also, they can be easily compressed and put into a small container,
unlike solids and liquids.
Since there is a lot of space between the particles, different gases can
diffuse into each other easily.
The kinetic energy between the particles is the maximum in the case of
gases. Therefore, the particles move around freely at high speed and
there is no fixed shape of gases.
Difference in the characteristic of states of matter
Solid Liquid Gas
Definite shape Indefinite shape Indefinite shape
Definite volume Definite volume Indefinite volume
Less forces of attraction Negligible force of
Maximum force of attraction
between particles compare attraction between
between particles
to solid particles
Cannot be compressed Cannot be compressed Can be compressed
Kinetic energy of particles is Kinetic energy of particles Kinetic energy of
minimum is more than solid particles is maximum
Particles cannnot move rather
Particles can slide over one Particles can move
they vibrate only at their fixed
another freely
position
Highest density Density is lower than solid Lowest denisty
Cannot flow Flow Flow

Can Matter Change its State?

Water exists in three states:
Ice – solid
Water – liquid
Water Vapor – Gas
This is an indication that matter can change its states.
Effect of Change of Temperature
What happens to matter when we heat it?
1. Solids:
As we heat solids, the kinetic energy between the particles of solids
increases which decreases the force of attraction between them.
They start vibrating and changing their positions. Slowly, due to heat the
particles become free and a solid converts into liquid.
Melting Point – The temperature at which solid melts to become a liquid
at atmospheric pressure. For Example, the melting point of ice is 273.16
Kelvin.
Fusion – The process of melting of a solid into liquid is called Fusion.

In the melting process, once a solid reaches its melting point, its
temperature does not increase further. So where does all the heat go?
The heat present in the solid at time of melting is used by the particles to
diminish the force of attraction between each other. The heat energy is
therefore considered as hidden.
Latent Heat – The heat energy which is used to break the force of
attraction between the particles of matter is known as latent heat. Since
the heat is hidden therefore it is called as Latent Heat.
Latent Heat of Fusion – The amount of heat energy 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.
Atmospheric Pressure – Pressure exerted by the weight of the
atmosphere.
2. Liquids:
Just like in solids, the kinetic energy of particles of liquid increases, the
force of attraction among them decreases and they start moving freely.
As we keep on supplying the heat, a point comes when the particles
overcome the forces of attraction completely.
This is when a liquid starts changing into gas.

Boiling Point - The temperature at which a liquid starts boiling at the

atmospheric pressure is known as its Boiling Point. For Example, The
boiling point of water is 373 Kelvin.
Latent Heat of Vaporization – the amount of heat energy required to
change 1 kg of a liquid into a gas at atmospheric pressure at its boiling
point is known as Latent Heat of Vaporization.
What happens when we decrease the temperature?
1. Gases:
The kinetic energy between the particles decreases and they turn into a
liquid state.
Condensation / Liquefaction – The process of converting a gas into a
liquid by cooling down its temperature. For Example, The formation of
clouds is due to condensation of water vapor from Earth.
2. Liquids:
The kinetic energy between the particles decreases and they turn into a
solid state. For Example, The formation of ice.
Sublimation – change of state of a gas directly into solid and vice-versa is
known as sublimation. For Example, Camphor is a solid that directly
evaporates into the air without changing to a liquid state.
Therefore, by increasing or decreasing the temperature we can change
the states of matter into one another. Here is a diagram that sums this
up.

Effect of change of Pressure

By applying pressure, we can bring the particles of matter close to each
other thereby, increasing the force of attraction among the particles.
When we compress and decrease the temperature of a gas, the gas
changes into a liquid.
Dry Ice – Carbon dioxide in solid form is known as Dry Ice. It can directly
turn into gas by decreasing the pressure to 1 atmosphere.
Evaporation

We already know that –

Particles of matter are never at rest
Particles of matter possess different amounts of kinetic energy
The particles of liquids have more kinetic energy. Therefore, they are
able to overcome the forces of attraction and convert into vapor without
any external forces.
Evaporation – The phenomenon of change of a liquid into vapors at any
given temperature below its boiling point is called Evaporation.
Evaporation is different than boiling, as shown in the figure below.

Factors Affecting Evaporation

Condition Rate of Evaporation Reason
Particles have more space
Increase in Surface
Increases and thus can evaporate
Area
easily
Increase in Kinetic energy among the
Increases
temperature particles increases
Water content in air
Increase in humidity Decreases increases and so evaporation
decreases
Water vapours are blown
Increase in wind speed Increases away by winds allowing more
evaporation
How evaporation causes cooling?
The process of evaporation uses the energy of the liquid particles.
Therefore, the particles absorb energy from the surroundings in order to
compensate the energy that is being lost in the process of evaporation.
This results in cooling of the surrounding area.

For Example:
Our palms feel cool when we put some acetone (nail paint remover) on it
People sprinkle water on their roofs or ground on sunny days to cool the
area
We are able to sip hot tea faster in a saucer than in a cup
Why people wear cotton clothes in summer?
We perspire more in summer. As the sweat evaporates it takes energy
from our body surface and keeps our body cool. Cotton can absorb the
sweat easily and exposes it to the atmosphere causing evaporation to
take place easily. This, in turn, keeps us cool in summer days.
Why water droplets appear on the surroundings of a glass with ice-cold
water?
There are water vapours present in the air. When they come in contact
with the walls of the glass that has ice-cold water in it they condense. As
a result, their state changes from gaseous state to liquid state thus
forming tiny water droplets on the walls of the glass.
The Five States of Matter
By far we have discussed the three states of matter – Solid, Liquid, Gas.
But, scientists have discovered that there are two more states of matter
–
Plasma
Bose-Einstein Condensate

Plasma
It is a state of matter in which the particles are super excited and super
energetic. They are in the form of ionized gases.
For Example – Fluorescent tubes and neon light bulbs consist of plasma
The neon bulbs contain neon gas and there is another gas such as helium
in the fluorescent tube. As electricity is passed in the tube or the bulb,
these gases get ionized and this creates the plasma inside them that
glows.
In fact, the Sun and the stars glow because they plasma is present in
them. Here are some examples of Plasma:

Bose-Einstein Condensate (BEC)

It is the fifth state of matter discovered by Albert Einstein on the basis of
the studies conducted by an Indian scientist Satyendra Nath Bose.
BEC is formed by condensing gases of extremely low densities to much
lower temperatures.
Important Measurement Units
SI Unit of Mass Kg (Kilogram)
SI unit of Volume m3 (cubic meters)
Common unit of Volume L (Liters)
Kelvin
0O C = 273.16 K or 273 K
SI unit of temperature
(approximately)
Kelvin = Celsius + 273
Si unit of Pressure Pa (Pascal)
Atmosphere (atm)
For measuring pressure 1 atm = 1.01 X 105 Pa
exerted by Gas Normal Atmospheric Pressure = 1
atm (at sea level)