La chimica

Materie:	Appunti
Categoria:	Inglese
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Data:	12.06.2007
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INGLESE CHIMICA

ALCHEMY:
The period of chemical history is called alchemy. It had basically two aims. The production of an elixir which geve health to who drank it and the production of gold. That became the main priority of alchemy. Alchemy had two major technical obstacle stopping it: the failure to consider mass an important property in chemistry and the difficulties in verifying and controlling the degrees of heat.
The chemical process were: distillation, pounding, boiling, and grinding.

PLASTICS:
The plastics are cheap, resistant corrosion, easy to bend and are lightweight. Plastics are produced by polymerization, a process of creating network and molecules.
When heated the process the polymers, plastics are divided into two many types: thermoplastics resistant and thermoresistant resins.
Thermo plastics resistant for example are infusible and insoluble.

CHEMSTRY:

Chemistry studies the chemical structure, proprieties and transformations of minerals, vegetables and animal. It has an important role in modern society. There are a multitude of minerals created by chemistry industry: plastics, fertilizers, pharmaceutical products, insecticides, detergents and artificial fibres etc..
The incautious or indiscriminate use of its can be danger the nature and the environment.

(mancano: “matter and compound” e “the branches of chemistry ” del primo e secondo trimestre)

TERZO TRIMESTRE

ELEMENTI E FORMULE:
there are more than 100 element of witch 89 are present in nature and, 11 are produced synthetically in the laboratory. Each element has a specific name, specific number and atomic number.
Each chemical symbol generally derives from the first letter of element.
Formulas are a combination of chemical symbols and the relative number of atoms in each element.
For example, in water are present 2 atom of hydrogen and one atom of oxygen.

LIPIDI:
Lipids are a organic molecules conteining oxygen, hydrogen and carbon.
They are insoluble in water but soluble in alcol.
During digestion fats are broken into glycerol and fatty acid. Usually it is more difficulty for the body to digestion fast.
Fats are generally solid at normal temperature (25°C) but at higher temperature they start to liquefy.
Hard fat includes wax, beef and human fat. Soft fat includes all oil apart from mineral oils.

MASSA E DENSITà:
Mass is the measure of the quantity of matter and depends on the number of molecules conteinig.
Mass con be measured in Kilogram and this derivated
Density is a misure of the quantity if space a substance occupeies. The smaller the space into which the mass is concentrated many larger is the density. Every substances has its own different density and this helps to identify substances.
Density is calculated by dividing the mass of a substance by its volume for example kilograms divided litres.

PASSAGGI DI STATO:
The world around us, is divided into three state of the matter: liquid, gasses and solid.
Solid have a definite mass and volume. Liquids have a definite mass and volum and Gasses have only definite mass.
These different is constructed of invisible particles move freely without limit.
The liquids the freedom of movement is reduced while (mentre) in the solids the particles are almost immobile at last (infine) in the gasses the particles con move freely without limit.
The different change in the state of matter are: solidification, vaporisation, condensation and sublimation.
Solidification when the particles which have been speeded up then slow down again and move closer together.
Vaporisation takes place slowly over a range of temperature.
Condensation also takes place over a range of temperature.
Sublimation is when a solid changed directly into vapour.

TAVOLA PERIODICA:

The Russian scientist Mendeleyev was the first to catalogue elements according to their atomic weight. Element with same colour have a similar proprieties.

When two substances with precise characteristics are interact they from a new substances with different characteristics , these transformation in chemical are called: chemical reactions.
More than three-quarter of the natural element are metals but exist in an elementary state in nature, for example silver, platinum, gold.
Elements heaving proprieties of both metals and non metals are called metalloids.