CLASS VIII ACHEMISTRY

NOTES CHAPTER - 1. MATTER

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Matter Any thing that has mass and occupies space is called Matter.

Matter include both Living and Non-living both but living are known as Living Matter such as the cells, organs, animals or human being ,all plants and animals.

Matter are variable in shape , volume, texture(look) and other characteristics.

Light, the sounds electricity are not matters.

Vacuum is space where there is no matter.

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Different States of matter

On the basis of physical properties, matter is divided into three states.

1. Solid

2. Liquid

3. Gas

Physical properties- Physical properties can be observed or measured without changing the composition of matter.

They are used to observe and describe matter.

Physical properties include – appearance, texture, colour, odour, melting point ,boiling point ,density, solubility, polarity, and many others.

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Solid State

The particles of slid are closely packed because their particles passes highest intermolecular force of attraction and least inter molecular spaces between the particles solid matter.

Solids have a fixed mass, Volume and Shape.

Depending on what they are made up of solids have different characteristics.

They may be rough or smooth, hard or soft, shiny or dull, elastic or rigid and so on.

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Liquid state

The particles within liquids are more loosely packed than they are in solids because the passes intermolecular force of attraction and intermolecular space is greater than that of solids.

• It is almost impossible to compress liquids.

• Liquids have fixed mass and volume.

• They do not have definite shape.

• They take the shape of container.

• They can flow.

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Gases state

There is very little arrangement of particles within a gas because their particles posses least intermolecular force of attraction and passes higher intermolecular space.

• Gases have mass but they do not have fixed volume.

• Gases have mass but they do not have fixed shape.

• They can be compressed by applying pressure.

• They can flow.

• They spread throughout the space available to them.

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Plasma Plasma is a hot ionized gas consisting of approximately equal

numbers of positively charged ions and negatively charged electrons ions.

Plasma is used in television, neon , signs and fluorescent light.

Stars lightning and some flames consist of plasma.

A plasma may be produced in the laboratory by heating a gas to an extremely high temperature, which causes such vigorous collision between its atoms and molecules that electrons are ripped free yielding the electrons and ions.

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Bose-Einstein Condensates(BEC)

In 1924 Albert Einstein and Satyendra Nath Bose predicted the Bose-Einstein Condensates(BEC) as fifth state of matter.

In a BEC matter stops behaving a independent particles and collapses into a single quantum state that can be describe with a single uniform wave function

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Properties Solid Liquid Gas

Shapes and volume Solids have definite shape and volume

Liquids have definite volume but no definite shape

Gases have neither definite shape nor definite volume

Rigidity Solids are rigid Liquids are not rigid Gases are not rigid

Fluidity Solids cannot flow Liquids can flow from higher concentration to lower concentration

Gases can flow in all directions

Compressibility Solids cannot be compressed appreciably

Liquids can be easily compressed

Gases can be easily compressed

Intermolecular force of attraction

Solids have maximum intermolecular force of attraction in between their particles

Liquids have inter molecular force of attraction less than solids

Gages have least inter molecular force of attraction in between their particles

Storage Solids can be stored without a vessel

Liquids cannot be stored without a vessel

Gases can be stored in closed vessels only

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Fluidity

The capacity of liquid and gases to flow is called fluidity.

Some liquids are more fluid than others.

Relation between fluidity and viscosity.

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Viscosity

The viscosity of a fluid is a measure of its resistance to flow at a given rate for liquids it corresponds to the in formal concept of Thickness.

It mean in simple language that higher the viscosity of a liquid lower the fluidity.

Viscosity .∝

Viscosity is a measure of how thick a liquid is.

Water is less viscous liquid than oil syrup and honey.

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Some matters are exist into three states

Water:

• Only water can be exist in all the three states naturally.

• In solid state - ice

• In liquid state - water

• In gaseous state - water vapour.

Carbon dioxide:

• In solid state - Dry ice

• In liquid state - (under pressure)

• In gaseous state - CO2.

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Kinetic molecular theory of matter

Kinetic molecular theory of matter states that matter is made up of small particles that are in a state of constant motion.

IT explains how matter exists in one state and transforms from one state to another.

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Postulates of kinetic The theory

Matters are made up of particles-atoms and molecules-which constantly vibrate or move randomly.

All the particles have kinetic energy as they are vibrating or moving all time.

There are spaces between the particles which keep them together. They are knows as inter particle force of attraction.

The change in state or phase occurs when there is a change in the energy of the particle.

When the temperature is increased ,the energy of the particle increases and they move faster, colliding frequently with one other and the walls of the container. The inter particle spaces increase, and a change in the state of matter occur.

When the temperature is lowered ,the energy of the particle spaces become smaller and a change of state in the reverse direction may take place.

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Brownian movement

Robert brown was give the concept of Brownian movement.

The erratic random movement of microscopic particle in a fluid as a result of continuous bombardment from molecules of the surrounding.

He studying that the pollen grains mixed with water. Under the microscope , brown observed that the pollen grains constantly moving although the water was not disturbed .this is because the water molecules are continuously moving ,hitting against the pollen grain s and pushing them in all directions. This random movement of particles is knows as Brownian motion.

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Diffusion Diffusion – Diffusion is a natural process of movement of particles from higher

concentration to lower concentration until equilibrium maintain.

The degree of diffusion depends on the state of matter.

Solids are rigid and do not diffused into each other.

Some liquids such a water and honey diffused into each other.

Some such as water and oil do not diffused into each other.

Molecules of gas easily diffused into the inter-particle spaces of another gas.

Diffusion also occurs between different state of matter.

Solids and liquids can diffused through gases.

Solids and gases can diffused through gases.

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Explanation of the state of matter

All the three states of matter depends on two factors:

a) Intermolecular force of attraction.

b) Intermolecular space between the particles of matter.

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Explanation for change of state: The three states of matters are inter convertible, that is matter can change from

one state to another.

Inter conversion between the states of matter can be brought about by a change in temperature and presser.

Change in temperature:

Increase in temperature of liquids can change its state into gaseous state this process is called vaporisation or evaporation.

Evaporation take place at all temperature but very slowly.

When temperature of solid increases it converts into liquid this process is called melting or fusion.

When temperature of liquid decreases than it converts into solid states. This process is called freezing or solidification.

The change of state from gas to liquid on cooling is called condensation or liquefaction.

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NOTE – when temperature of a liquid or solid state of matter increases, then the particles of respective states absorbs energy and changes into another state.

EG- ICE WATER

heating

(absorbs heat energy)

when temperature of a liquid or gas decreases then the particles of respective states of matter releases energy and changes into another state.

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Boiling point:

The temperature at which liquids boils is called boiling point of liquids.

Boiling point is variable for different liquids.

Melting point:

The temperature at which solids melts is called its melting point.

Melting point varies with different solids.

Condensation point:

The temperature at which gaseous particles condenses into liquids is called its condenses point.

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Sublimation:

It is a process in which solid substances converts into gaseous state without melting into liquid.

For example: Naphthalene and iodine.

Deposition:

The reverse process of the change of state from gaseous to solid on cooling without changing into liquid is called deposition.

For example: Deposition of gaseous water vapor as solid frost on a window.

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Change in pressure:

The state of matter can we change by decreasing or increasing the pressure of matter.

It applies only to some substances in certain state of matter.

For example: liquid petroleum gas(LPG) is used as a fuel in homes and vehicles.

It is a mixture of butane and propane.

It becomes a liquid when pressure is applied, LPG is sealed under pressure in cylinders.

When the valve is opened, the pressure decreases and liquid becomes a gas again.

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Law of conservation of mass:

The law of conservation of mass states that mass can neither be created nor destroyed by chemical reactions or physical transformations.

According to their the mass of the products in a chemical reaction must be equal to the mass of the reactants.

A+ B C + D

Total mass of the reactants = total mass of the products

Example of combustion of magnesium

magnesium + oxygen magnesium oxide

(Mass of reactant = mass of magnesium oxide)

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