States of matter is anything that occupies space. Matter exists in three states: solids, liquids and gases. Matter can be changed in various ways which includes physical, chemical and nuclear changes.
a) Physical changes– they are
normally reversible and no new substances formed. Examples are;
(i) Change of state such as
melting and vaporization
(ii) Thermal expansion due to
heating
(iii) Dissolving solids in
liquids
(iv) Magnetizing
(v) Charging electrically
b) Chemical changes– they are
irreversible and new substances are formed Examples are;
(i) Changes caused by burning
(ii) Changes occurring in some
chemicals due to heating e.g., mercuric oxide
(iii) The reactions resulting
from mixing chemicals to form other substances.
c) Nuclear changes– these are
changes occurring in nuclear substances which give off some particles i.e.,
Uranium and Radium. As this happens, they change into other substances.
Particulate nature of matter is made up of millions of tiny particles which
cannot be seen with naked eyes. These particles are called atoms and are made
up of sub-atomic particles called protons, neutrons and electrons. Atoms join
together to form molecules.
Movement of particles move
from one region to another by the process of diffusion. Diffusion is the
movement of molecules from regions of high concentration to regions of low
concentration until an equilibrium is reached or achieved. Gases diffuse
faster or readily than liquids. The rate of diffusion depends on the manner of
arrangement of individual particles.
Solids
Individual atoms in solids have a
small space between them hence their forces of attraction are very strong. They
vibrate in their fixed positions and this gives solids a fixed shape.
Liquids
Forces of attraction between
liquid molecules are not as strong as in solids where motion is not restricted.
They collide with each other as they move about. They take the shape of the
container they are put in hence have no definite shape.
Gases
Molecules of atoms in gaseous
state are further apart experiencing very small forces of attraction. This
makes them almost completely free from each other. We say they are independent
in space. Gases have no definite shape and volume but they take up the space
and volume of the container they are put in.
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