# CBSE Class 9 Science Chapter 1 Revision Notes

Chapter 1:Matter In Our Surroundings Revision Notes

• Matter is anything that takes up space, has mass, and can be sensed by the senses.
• Air, earth, fire, sky, and water are the five basic elements (the Panchtatva) according to an Indian ancient philosopher.

Characteristics of Particles of Matter

• Made up of minuscule particles.
• Between particles, there are empty gaps.
• Particles are always moving.
• Forces of attraction bind particles together.

## Matter in its various states

Basis of Classification of Types

• Depending on the particle arrangement
• On the basis of particle energy
• Depending on the particle distance

There are five different states of matter.

• Solid
• Liquid
• Gas
• Plasma
• Condensate of Bose-Einstein

Source

(I) SOLID

• The mass, volume, and shape of the object are all fixed.
• The shortest inter-particle distances exist.
• Incompressible.
• Do not diffuse and have a high density
• The strongest attraction forces exist between particles.
• The constituent particles are tightly packed.

(II) LIQUID

• There is no defined shape, but there is a fixed volume and mass.
• The spacing between particles are bigger than in solids.
• Almost impenetrable.
• The density of liquids is lower than that of solids, allowing them to diffuse.
• The attraction between particles is weaker than in solids.
• Particles in the constituents are less densely packed.

(III) GAS

• Neither the shape nor the volume are fixed.
• The distances between particles are the greatest.
• The material is extremely compressible.
• The density is the lowest and most diffuse.
• Attraction forces between particles are the weakest.
• Particles in the mixture are free to move about.

(IV) PLASMA

• An ionised gas is referred to as plasma.
• Magnetic fields impact plasma, which is a very good conductor of electricity.
• Plasma, like gases, has an amorphous shape and an amorphous volume. Ionized gas, for example.

(V) CONDENSATE BOSE-EINSTEIN

• BECs are states of matter that can exist at extremely low temperatures.
• In 1995, the scientists who worked on the Bose-Einstein condensate were awarded the Nobel Prize for their efforts.
• The BEC is concerned with molecules that are extremely near to one another (even closer than atoms in a solid).

Solid Property Explanation from a Microscopic Perspective

• Because the particles are fixed into place, solids have a defined shape and volume.
• Because the particles cannot move or slide past one another, solids do not flow smoothly.
• Because there is minimal empty space between particles, solids are difficult to crush.

Explanation of Liquid Properties at a Microscopic Level

• Because there is limited empty space between particles, liquids are difficult to compress and have a defined volume.
• Because the particles may move/slide past one another, liquids flow readily.
• Because the particles may move/slide past one another, liquids flow readily.

Microscopic Explanation of Gases’ Properties

• Because there is so much open space between particles, gases are easily compressed.
• Gases flow freely because particles pass through each other at random.
• Because particles can travel past one another (non-evaluative), gases have an unlimited shape and volume.

Explanation of Plasma Properties at the Microscopic Level

• Because the particles can move past one another, plasmas have an indeterminate shape and volume.
• Because there is so much open space between particles, plasmas are easily compressed.
• Because plasmas are made up of lenses, they are good conductors of electricity and are impacted by magnetic fields.

BEC Properties: A Microscopic Explanation

• Because particles exist at such low temperatures, they are less energetic than solids.
• Because they are trapped in the same space, particles are virtually indistinguishable.
• Because particles may move without friction in BEC, it demonstrates extreme fluidity.

## Changes in the states of matter

• Water can exist in three states of matter: liquid, solid, and gas.
• As if made of ice, Water, for example, is a liquid, andAs water vapour, it is a gas.
• Sublimation is the transformation of a solid into vapours when heated and back to a solid when cooled. Ammonium chloride, camphor, and iodine are examples.

(a) The impact of temperature changes

• The influence of temperature on heating a solid varies based on the nature of the solid and the conditions under which the change must occur.
• As the temperature of solids rises, the kinetic energy of the particles rises, overpowering the forces of attraction between the particles, causing the solid to melt and become a liquid.
• The melting point of a solid is the temperature at which it melts to become a liquid at atmospheric pressure.
• Ice has a melting point of 273.16 K.
• Melting, or the transition from a solid to a liquid state, is also known as fusion.

(a) The Impact of Pressure Changes

• The condition of matter can be changed by increasing or lowering pressure. Gases can be liquefied by applying pressure and lowering the temperature.
• Under high pressure, solid carbon dioxide (CO2) is stored.
• When the pressure is reduced to 1 atmosphere, it is transformed to a gaseous state without passing through the liquid condition. This is why solid carbon dioxide is also referred to as dry ice.
• Heat that isn’t visible.
• During a transition of state, the concealed heat destroys the force of attraction between the molecules.
• Fusion To turn 1kg of solid into liquid, you’ll need a lot of heat.
• Vaporisation The amount of heat energy necessary to turn 1 kilogramme of liquid into a gas at atmospheric pressure at its boiling point
• As a result, we can say that pressure and temperature decide whether a thing is solid, liquid, or gas.

Boiling & Evaporation

• Matter particles are never at rest and are continuously moving.
• There are particles with variable quantities of kinetic energy in any gas, liquid, or solid at any given temperature.
• In liquids, a small fraction of particles at the surface with higher kinetic energy are able to break free from the forces of attraction of other particles and become vapour.
• Evaporation is the transformation of a liquid into vapours at any temperature below its boiling point.

Evaporation-Related Factors

• With an increase in surface area, the rate of evaporation increases.
• As the temperature rises, more particles gain enough kinetic energy to enter the vapour state.
• The amount of water vapour present in the air is referred to as humidity. At any given temperature, the air surrounding us can only carry a certain amount of water vapour. The rate of evaporation slows down when the amount of water in the air is already high.
• The higher the wind speed, the more evaporation occurs.
• Cooling is caused by evaporation.
• To make up for the energy lost during evaporation, liquid particles absorb energy from their surroundings.

Boiling vs. Evaporation

• Boiling is a phenomenon that affects a large number of people. Particles from the liquid’s bulk (whole) transition to a gaseous condition.
• Evaporation is a phenomena that occurs at the surface of the water. Particles from the surface accumulate enough energy to overcome the liquid’s attraction forces and transition to the vapour stage.

## Kelvin and Celsius Temperature Scales

• Kelvin is the SI unit of temperature.
• 0 degree celsius = 273.16 K
• Because the Kelvin scale of temperature always has a positive sign, it is considered to be a superior scale than Celsius.
• The atmosphere (atm) is a measurement unit for the pressure exerted by a gas. Pascal (Pa) is the SI unit of pressure: 1 atmosphere = 1.01 (10 to the power 5) Pa.
• Atmospheric pressure is the pressure of air in the atmosphere. At sea level, the atmospheric pressure is 1 atmosphere, which is used to determine the normal atmospheric pressure.

Source:

]]>