|
|
עמוד:4
Introduction What do all materials around us have in common ? What makes one substance different from another ? There is an immense variety of materials in the world , with all their different properties . How is it created ? All matter is made up of particles . The particles of matter are in constant motion , and forces are at work between them . The particulate structure of matter enables us to explain different phenomena in the material world , such as the dispersion of the scent of perfume in a room , the elongation of a metal bar upon heating , and condensation of water . The particulate structure of matter also explains the common properties of gases , liquids and solids , and the differences between them . In this chapter we will take a closer look at the mysteries of the particles of matter , and we will ask ourselves : What are those particles ? How can we use them to explain the variations between different materials or the immense diversity of materials in the world ? We will also learn about the work of one of the most important scientists in the field of chemistry , Dmitri Mendeleev , who studied the world of matter and organized the elements in a table – the periodic table . Mendeleev’s work paved the way for a vast volume of research and discoveries in the field of chemistry , and to this day it forms the basis for the work of chemists and researchers in many other fields as well . Solid Gold and iron are different substances , but their particulate structure is similar : the particles are tightly packed and arranged in a regular pattern . They vibrate in place and do not move from one place to another . Liquid Oil and water are different substances , but their particulate structure is similar : the particles are tightly packed but are not arranged in a regular pattern . They are able to move from place to place , sliding over one another and changing places . Gas Carbon dioxide and oxygen are different substances , but their particulate structure is similar : the particles are very distant from one another , they move fast and freely in all directions .
|
|