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| The sound waves |
It is very important to know that the human ear differentiate between the sounds that reach it through the different factors which are the sound pitch , the sound intensity and the sound quality .
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| The sound wave |
The sound
You should know that the sound is an external factor that affects the ear causing the sense of hearing . And it produced due to the vibration of the bodies , and it stops when the vibrating bodies stop their vibration .
The suitable conditions for the fossils formation
It is very important to know that the organism body must be buried immediately after death in a medium that preserves it from the decomposition . The organism must have hard skeleton .
The Fossils
It is very important to know that the fossils are the traces and the remains of the living organisms which are preserved in the sedimentary rocks .
The water pollution
It is very important to know that the water pollution is the addition of any substance to the water which causes continuous gradual change in the water properties and affects the health and the life of the living creatures .
The physical properties of the water
It is very important to know that the water has a higher melting point , boiling point , and heat of vaporization than most common liquid . This fact indicates that there are strong forces of attraction between the adjacent water molecules .
