Или подскажите как правильно сделать? задайте 4 типа вопроса ко всему тексту: 1) общий вопрос; 2) специальный вопрос; 3) альтернативный; 4) разделительный; physical properties of petroleum the colour of petroleum varies from light yellow to red, while some very dark grades are opaque. the higher the specific gravity, the darker the oil. the nature and composition of crude oil usually determines its odour. unsaturated hydrocarbons, sulphur and certain nitrogen compounds are responsible for disagreeable odours. crude petroleum from the ussr, rumania and california has an aromatic odour. pennsylvania petroleum has an agreeable gasoline-like odour. other oils vary in odour depending on the quantity of light hydrocarbons present in the oil, and of the impurities present. the petroleum from south texas and mexico has a strong disagreeable odour, due to hydrogen sulphide and other sulphur compounds. petroleum is lighter than water. the specific gravity is influenced by physical factors and by the chemical composition of the crude oil. it varies from 0.7684 to 0.992. the viscosity, or the measure of the resistance to flow, is an important factor with lubricating oils. crude petroleums are quite different in viscosity. some are very mobile, while others, like mexican crude, are quite viscid. heavy petroleum in general is composed to a large extent of these hydrocarbons. the viscosity increases with the density. the viscosities of oils of the same specific gravity, but from different sources, are not always the same. this is due to the difference in chemical composition.
Специальный: What kinds of petroleum are mentioned here?
Альтер: Does petroleum have many or few characteristics?
Раздел: This text is about petroleum, isn't it?