IMPORTANT TERMS

Matter-                                  Anything that has a mass and occupies space is called matter.

Volume-                     The amount of space occupied by something is called volume. Volume of a liquid is measured by an instrument called graduated cylinder.

Mass-                                  The amount of matter contained in an object is called its mass. Mass of an object is measured by a beam balance.

Density-                          Mass per unit volume is called density.

Contraction -                    The decrease in size of matter on cooling is called contraction.

Expansion -                        The increase in size of matter on heating is called expansion.

Immiscible Liquids-        Those pair of liquids which do not get mixed in each other are called immiscible liquids e.g. oil and water.

Miscible Liquids-           Those pair of liquids which get mixed in each other in all proportions are called miscible liquids e.g. milk and water.

Flammable liquids-          Liquids that catch fire easily are called flammable liquids e.g. Petrol, alcohol.

Non-flammable liquids-   Liquids that do not catch fire easily are called non-flammable liquids e.g. Water, milk.

 

CLASSIFICATION OF MATTER

PHYSICAL STATE	SHAPE	VOLUME	FORCES OF        ATTRACTION	SPACE BETWEEN       THE PARTICLES
Solid	Fixed	Definite	Very strong	Close together
Liquid	Not fixed	Definite	Intermediate between solids and liquids	Intermediate between solids   and liquids
Gas	Not fixed	Indefinite	Very weak	Far apart

 

Dissolving solids, liquids and gases in water

Water is called a universal solvent as it dissolves most of the substances in it.

Solids - Some substances get dissolved in water easily and form solution e.g. salt and sugar get dissolved in water to form a solution. However, some substances do not get dissolved in water e.g. chalk powder, sand etc.

Liquids – Some liquids are soluble in water e.g. milk, fruit juice gets mixed in water. However, some liquids like petrol, diesel does not get mixed in water.

Gases – Some gases get dissolved in water e.g. oxygen and carbon dioxide are slightly soluble in water. However, some gases do not get dissolved in water e.g. hydrogen, nitrogen etc.

 

CHANGE OF STATES     

Evaporation -      Changing of a liquid into gas is called evaporation.

Condensation -   Changing of a gas into liquid is called condensation.

Freezing -             Changing of a liquid into a solid is called freezing.

Melting -              Changing of a solid into a liquid is called melting.

Effect of change of temperature

Rise in temperature

A solid converts to liquid on heating.

A liquid converts to gas on heating.

Speed of particles and space between the particles increases on heating.

Fall in temperature

A gas converts to liquid on cooling.

A liquid converts to solid on cooling.

Speed of particles and space of particles decreases on cooling.

 

CLASSIFICATION OF CHANGES

Physical Change-            Changes in which no new substances are formed are called physical changes. They are generally reversible.

Chemical Change-        Changes in which new substances with different properties are formed are called chemical changes. They are generally irreversible.

Reversible Change-        Changes that can be carried out in reverse direction.

Irreversible Change-      Changes that cannot be carried out in reverse direction.

Causes that can bring a change

Change in shape -                   e.g. Change in shape of balloon by blowing air in it.

Change in size -                       e.g. on keeping a balloon in hot water it expands.

Change in physical sate -        e.g. Wax melts on heating.

Change in position -                e.g. on throwing a small piece of rock from one place to another.

Change in colour -                   e.g. on heating a piece of iron it becomes red.

Change in internal structure - e.g. on cooking food the internal structure of food changes.

 

INTRESTING FACTS

Generally liquids contract on cooling but water expands on cooling and forms ice.

Liquids, solids and gases are the most common 3 states of matter on Earth. However, much of the matter of universe is in the form of hot plasma the fourth state of matter.