Introduction
Anything which
occupies space and has mass is termed as matter. Air and water, salt and
sand, cloud, tree, human, animals etc. The universe is made up of matter.
The matter is composed of very very tiny particles
called atoms. It can be seen through the electron microscope.
Physical nature of matter
1.
Matter is composed of very
tiny particles.
2.
The particles have space between
them called intermolecular space.
3.
The particles are constantly
moving.
4.
These particles attract each
other.
Classification of matter
Matters are found in four natural states: Solids, liquids, gases and plasma. The fifth state of matter is the artificial called Bose-Einstein condensates.
On the basis of physical
properties matter are classified in three categories.
A.
Solid
B.
Liquid
C.
Gas
Solid:
- Solid have strong molecular
force.
- Solid have a definite shape.
- Intermolecular space in solid is
less than liquid and gas.
Liquid-
- Liquid have weak
intermolecular force than solid.
- Liquid doesn’t have a definite
shape but have a definite volume.it acquires the shape of the container on which it is
kept.
- Liquid can flow.
Gas-
- Gas have a weak intermolecular
force and high compressibility.
- Gas don’t have a definite shape
and volume.
- Intermolecular space is very
high in gas.
Interchange of state of matter
A change of state of matter is a physical change in a
matter. They are reversible changes and do not involve any changes in the
chemical properties of the matter.
Common changes of the state include freezing, melting, sublimation, condensation, and vaporization.
Melting
Melting, or fusion, is a physical
process that results in the phase change of a substance from a solid to a
liquid.
Freezing
Freezing is a phase change where a
liquid turns into a solid when its temperature is lowered below its freezing
point.
Sublimation
Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state solid
Solid carbon dioxide (CO2)-called dry ice 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 an example of sublimation process.
Condensation
A process IS called condensation where water vapour becomes liquid. It is considered as the reverse of evaporation, where liquid water converted into vapour. It happens one of two ways: Either the air is cooled upto dew point or it becomes so saturated with water vapour that it cannot hold any more water.
Vaporization
Vaporization, the conversion of a substance from the liquid or solid phase into the gaseous (vapour) phase.
What happens
inside the matter during the change of states?
On
increasing the temperature of solids, the kinetic energy of the composed particles increases.
As a result of an increase in kinetic energy, the particles start vibrating with
greater speed.
The
energy supplied in the matter by heat overcomes the forces of attraction between the
particles. The particles leave their fixed positions and start moving more
freely. A stage arrives when the solid melts and is converted to a liquid.
Change of
States of Matter
Matters can change their state. A solid changes into liquid and a liquid changes into a gas. Metals, which are in solid-state, turn into liquid on heating and turn into vapour on
further heating.
The change of state of matters depending upon two factors:
Temperature
Pressure
Effect of temperature on states of matter:
D. (Solid → Liquid) Solids change into liquid with increase in temperature.
E. (Liquid → Gas) A liquid changes into gas by increase in temperature.
F. (Gas → Liquid) Gas changes into liquid by decrease in temperature.
G. (Liquid → Solid) Liquid changes into solid by decrease in temperature.
Effect of pressure:
Solid: There is absolute no effect of
pressure on solids.
Solids are non-compressible,
i.e. solids is compressed as there is no space between their particles
which could allow compression.
When the pressure is increased
on any solid, it is deformed in shape and finally broken.
Liquid: It has no effect on
pressure.
Liquids cannot be compressed (non-compressible) because there is very little intermolecular space between their
particles to get compressed.
Gas: The volume of gas
decreases with an increase in pressure.
Since there is a lot of space
between the particles, gas is highly compressible. A large volume of gas substances can be
compressed into a small volume. Because of this nature high compressibility, gas
is transported easily after being compressed to a small volume in cylinders.
Natural gas is compressed into small volumes .which is packed in cylinders. It is used widely as fuel to run vehicles. Because of this compression, it is called Compressed Natural Gas or simply
known by CNG (Compressed Natural Gas).
Oxygen is compressed in small cylinders, which is used to save a life in hospitals.
Latent heat
Latent
heat is defined as the heat or energy that is absorbed or released during a
state change of a substance.
Latent heat of fusion
The amount of heat required
to convert one unit mass of a substance from the solid phase to the liquid
phase.
Latent heat of vaporization
The amount of heat required
to convert one unit mass of a substance from the liquid phase to the gas phase
Evaporation
Evaporation is the process in which matter changes its state from a liquid
state into a gaseous state of matter
(vapor). This process requires some heat energy.
HOW DOES EVAPORATION CAUSE COOLING?
The liquid keeps on evaporating. The particles of liquid absorb heat energy from the surroundings to regain the energy lost during evaporation. This absorption of heat energy from the surroundings make the surroundings cold.
Example: when you put some acetone (nail polish remover) on your palm. The particles of acetone receive energy from your palm or surroundings and evaporate causing the palm to feel cool.
Factors That Affect the Evaporation
1. Temperature: rate of evaporation increases with temperature increases, Temperature and rate of evaporation are directly proportional to each other.
2.
Surface area: the rate of evaporation increases with an increase in surface area. The surface area
and rate of evaporation are directly proportional to each other.
3.
Humidity: The evaporation rate decreases with an increase in humidity. Humidity and the rate
of evaporation are inversely proportional.
4. Wind speed: Increase in wind speed increases evaporation. Wind speed and rate of evaporation are directly proportional to each other.
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