化工与环保.ppt

1、化工与环保Subject English forChemical Engineering and Enviromental ProtectionContentsI. ChemistryII. Unit Operation and EquipmentIII. Chemical Technologies（ Important Industrial Chemical Products ）IV Enviromental ProtectionV Scientific Writing and Literature SearchLect. One Elements and Compounds Element

2、s are pure substances that cannot be decomposed into simpler substances by ordinary chemical changes At presnt time there are 109 known elements. Some common elements that are familiar to you are carbon, oxygen, aluminium, iron, copper,nitrogen, and gold. The elements are the building blocks of matt

3、er 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 also comprise the entire universe. About 85% of the elements can be found in nature, usually combined with other elements Copper, Silver, gold, and ab

4、out 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 substances composed of two or more elements are called compounds. Compoun

5、ds 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. The compound carbon monoxide (CO) is composed of carbon and oxygen in the ratio of one atom of

6、 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 is composed of two atoms of hydrogen and one atom of oyg

7、en per molecule, which represents 11.2 percent hydrogen and 88.8 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 acid. No other compounds has all these exa

8、ct physical and chemical properties, they are charactristic of water alone. Compounds consisting of ions do not exist as molecules. Sodium chloride is an example of a non-molecular compound. Although this type of compound consists of large numbers of positive and negative ions, its formula is usuall

9、y represented by the simplest ratio of the atoms in the compound. Thus, the ratio of ions in sodium chloride is one sodium ion to one chlorine ion. Mixtures are formed simply by blending two or more substances together in some random proportion without chemically changing the individual substances i

10、n the mixtures. Homogeneous mixtures, usually called solutions, have a constant composition throughtout. Air is a gaseous solution of oxygen and nitogen, seawater is a liquid solution (primarily) sodium chloride dissolved in water, and brass is a solid solution of copper and zinc. Heterogeneous mixt

11、ures have regions with differing compositions. Salt with sugar, Water with gasoline, and dust with air, are all heterogenous mixtures. MatterMixtures Pure substancesHeterogeneousHomogeneousElements Chemical compounds专业英语的特点 词汇特点用词明确专一：如valve（阀），vapor（蒸汽），synthesize（合成） 句子特点句子结构复杂，且长句较多。 文体结构特点（1）描述具体、准确。如：Water is a colorless（2）用词造句简洁、明了。如：This construction is practicable only for small shells.（3）运用图表、公式、符号、缩写词语等来替代和简化文字描述。如：LNG, e.g.