- •Chemistry
- •Introduction
- •Some facts about chemistry
- •Some facts about atoms (I)
- •Some facts about atoms (II)
- •The atomic model
- •The nature of ceramics
- •Construction materials
- •The measurements in chemistry
- •The metric system
- •Isotopes
- •Words to be remembered:
- •Notes on the text:
- •Liquids(I)
- •Words to be remembered:
- •Liquids (II)
- •Words to be remembered:
- •Solid state (I)
- •Words to be remembered:
- •Solid state (II)
- •Words to be remembered:
- •Properties of solids
- •Notes on the texts:
- •Words to be remembered:
- •Organic chemistry
- •Word to be remembered:
- •Elementary carbon
- •Words to be remembered:
- •Notes on the texts:
- •Carbon dioxide
- •Words to be remembered:
- •Words to be remembered:
- •Hydrogen
- •Words to be remembered):
Words to be remembered:
interior therefore
opaque transparent
ductile branch
break conduct
insulator previously
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Solid state (II)
If we consider the fact known since the earliest studies of electric currents, we should remember that metals conduct electricity well and most materials do not.
It is only the discovery of electron that could help the scientists to understand some of these facts well. With the discovery of electron it was assumed that in metals some or all of the atoms had lost an electron and that in insulators such as glass they had not. The electrons in a metal proved thus to move freely, whereas the electrons in insulators do not. Why did this happen in metals? This very question had to await the discovery of quantum mechanics. The next question was: “How are the electrons arranged?”
As far as this question is concerned we can say that solids can be divided into two classes: crystalline and amorphous. Ir the crystalline group, which is the largest and includes the metals and most minerals, the atoms are arranged in a regular
way. In some metals (for instance copper and nickel) they are backed together. In other metals (such as iron, for example), they are arranged in the form of a cube. The commonest of the amorphous group of solids appear in glass, its atoms are put together in a more disordered way than those of a metal.
The structure of an amorphous material is much more difficult to discover than that of a crystalline solid and considerable effort is being made to learn more about the arrangement of atoms in such materials.
Much has been learned about solids but much is still to be learned. There is a number of problems which are to be solved. No wonder that many scientists have been working at this interesting, so-called “solid state” science.
Words to be remembered:
to consider copper
electric current considerable
discovery effort
to arrange to appear
for instanoe to solve
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Properties of solids
The molecules of solids are close to each other, they are vibrating in a fixed position. There is a strong force of attraction between molecules in a solid. Because of the strong attraction between molecules solids have certain properties. If we examined solids thoroughly, we should find that these properties are: tenacity, hardness, malleability and ductility.
Tenacity is a measure of solid’s resistance to being pulled apart. Steel has a high tensile strengths concrete has a much lower tensile strength. Hardness is a measure of a substance’s ability to scratch another substance. The diamond is the hardest solid, it being able to scratch all other substances.
Malleability refers to a solid’s ability to be hammered or rolled into thin sheets. Gold is famous for its malleability, copper, tin and aluminum being other examples of malleable materials.
Ductility is the ability to be drawn out in the form of wires.