Thermal Energy and States of Matter

Introduction to thermal energy and states of matter:

Matter available in three states – solids, liquids and gases.  Gases differ from the others in that gases  are not rigid and are highly compressible. Chemistry deals with the structure of matter and the changes which it takes, it is appropriate to know about  “ Matter”.

Matter may be defined as ‘Anything which occupies space and has mass.’  Some examples of matter are water, air, plants etc.  States of Matter is classified in two different ways.


Classification of states of matter


Physical classification of states of matter:

On the account of rigidity, volume and shape, matter is classified into solid, Liquid or gas.  These are the states of matter,

Solids are rigid substances which have definite shape and definite volume.

Example: A piece of metal, a wooden box etc.

Liquids have definite volume but not has definite shape.  They can  take the shape of the containers in which they are placed.

Example: milk, fruit juice etc.

Gases have no definite shape and definite volume.

Example: nitrogen, air etc.

Plasma is the fourth state of matter, it  contains  gaseous ions and it available at very high temperature.

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Chemical Classification of states of matter:

On the account of chemical composition, matter can be classified as element, compound or mixture.  These are the states of matter,

a) Elements:

These are the substances which cannot be further decomposed by ordinary chemical means.  These are about 116 elements known so far, out of which nearly ninety(90) are naturally occurring elements, while the rest are prepared artificially by the nuclear process.

b) Compounds: These are the substances which can be decomposed into two or more simple substances by ordinary chemical method.  A compound is formed by the combination of two or more elements.  A compound must has a definite chemical composition.  Examples: Water, Ethane, methane etc.

c) Mixtures: These are the substances which may be separated into their components by some physical methods.  In a mixture, the elements retain their properties.  Example; air, solution of water and salt etc.


Thermal energy


Due to the random movements of atoms and molecules, internal energy develops in a system, this part of the internal energy refers to Thermal energy.  The excellent source of thermal energy available to all living organisms is the sun, the sun’s thermal energy is increased by the nuclear fusion in the sun.  In the form of radiation thermal energy emitted by the sun, it is called Heat.  Thermal energy is the form of kinetic energy, which is produced by the random movements of molecules in matter.  Thermal energy may be increased or decreased.