文档介绍：化工与环保
Subject English for
Chemical Engineering and Enviromental Protection
Contents
I. Chemistry
II. Unit Operation and Equipment
III. Chemical Technologies( Important Industrial Chemical Products )
IV Enviromental Protection
V Scientific Writing and Literature Search
Lect. One Elements pounds
Elements are pure substances that cannot be posed into simpler substances by ordinary chemical changes
At presnt time there are 109 known elements.
mon elements that are familiar to you are carbon, oxygen, aluminium, iron, copper,nitrogen, and gold.
The elements are the building blocks of matter just as the numerals 0 through 9 are the building blocks for numbers.
To the best of our knowledge, the elements that have been found on the earth prise the entire universe.
About 85% of the elements can be found in nature, bined with other elements
Copper, Silver, gold, and about 20 other elements can be found in highly pure forms. Sixteen elements are not found in nature; they have been produced in generally small amounts in nuclear explosions and nuclear research. They are man-made elements.
Pure posed of two or more elements are pounds.
Compounds exist either as molecules which consist of two or more elements bonded together or in the form of positive and negative ions held together by the attractive force of their positive and negative charges.
pound carbon monoxide (CO) posed of carbon and oxygen in the ratio of one atom of carbon to one atom of oxygen.
Hydrogen chloride (HCl) contains a ratio of one atom of hydrogen to one atom of chlorine
Water is a colorless, odorless, tasteless liquid that can be changed to a solid, ice, at 0 ℃ and to a gas, steam, at 100 ℃. It posed of two atoms of hydrogen and one atom of oygen per molecule, which represents percent hydrogen and percent oxygen by weight. Water reacts chemically with sodium to produce hydrogen gas and sodium hydroxide, with lime to produce calcium hydroxide, and with sulfur trioxide to produce sulfuric a