3 Part One. The Predicate

Silicon Dioxide
Silicon is, next to oxygen, the most abundant element in the earth’s crust which occurs mostly in the form of oxides. Silicon dioxide (silica), SiO₂, occurs in nature in three different crystal forms: as the minerals quartz (hexagonal), cristobalite (cubic), and tridymitc (hexagonal).

Quartz is the most widespread of these minerals; it occurs in many deposits as well-formed crystals, and also as a crystalline constituent of many rocks, such as granite. It is a hard, colourless substance. Its crystals are identified as right-handed or left-handed by their face development and also by (he direction in which they rotate the plane of polarization of polarized light.

The structure of quartz is closely related to that of silicic acid, H₄SiO₄. In this acid silicon has ligancy 4, and is surrounded by a tetrahedron or four oxygen atoms, with one hydrogen atom attached to each oxygen atom. Silicic acid, which is a very weak acid, has the property of undergoing condensation very readily, with elimination of water. If each of the four hydroxyl groups of a silicic acid molecule condenses with a similar hydroxyl group of an adjacent molecule, eliminating water, a structure is obtained in which the silicon atom is bonded to four surrounding silicon atoms by silicon-oxygen-silicon bonds. This process leads to a condensation product with formula SiO₂, Since each silicon atom is surrounded by four oxygen atoms, and each oxygen atom serves as a neighbour to two silicon atoms. The structure of quartz and of the other forms of silica is described as consisting of SiO₄ tetrahedra, and each oxygen atom is a comer of two of these tetrahedra. In order to break a crystal of quartz it is necessary to break some silicon-oxygen bonds. In this way the structure of quartz accounts for the hardness of the mineral.

Cristobalitc and tridymitc are similarly made from SiO₄ tetrahedra fused together by sharing oxygen atoms, with, however, different arrangements of the tetrahedra in space from that of quartz. Tridymitc resembles ordinary icc in structure, with silicon atoms in the oxygen-atom positions; cristobalitc similarly resembles cubic icc.

Words and Word-Combinations to Be Memorized

account for, adjacent, arrangement, attach, closely, crystalline, deposit, dioxide, formula, fuse, granite, group, hydroxyl, identify, mostly, neighbour, position, quartz, be related to, serve, share, silicon, similarly, since, space, surround, together, undergo, weak

Ex. 6. Give the Uzbek equivalents for the following:

next to oxygen, mostly, the most widespread mineral, deposit, a well- formed crystal, constituent, a hard substance, identify something, right- handed, left-handed, rotate, the plane of polarization, polarized light, be closely related to, be surrounded by, a weak acid, undergo condensation, a hydroxyl group, an adjaccnt molecule, be bonded to, lead to, condensation product, neighbour, in order to break a crystal, account for, be fused together, share oxygen atoms, ordinary icc, resemble smth. in structure

Ex. 7. Give the English equivalents for the following:

kremniy dioksidi, tabiatda uchraydi, polarizatsiya tekisligini aylantiradi, kvarts tuzilishi, yaqin aloqada bo'lishi, atomga qo'shilganda, juda zaif kislota, kondensatsiyaga uchraydi, juda oson, har bir gidroksil guruhlari, kislota molekulasi, aloqa, olib keladi. kondensatsiya, sinish aloqasi, shu bilan tushuntiring, mineralning qattiqligi, kislorod atomlarini o'zaro bo'lishish, kosmosdagi turli joylar, tuzilishdagi muzga o'xshaydi

Ex. 8. Fill in the blanks with prepositions where necessary. of, for, in, with, to, by

1. Silicon occurs mostly ... the form ... oxides. 2. Silicon dioxide occurs... nature... three different crystal forms. 3. The structure of quartz is closely related ... that... silicic acid. 4. Silicic acid has the property... undergoing condensation ... elimination ... water. 5 SiOj each silicon atom is surrounded... four oxygen atoms. 6. To break a crystal... quartz it is necessary to break... some silicon-oxygen bonds. 7. The structure... quartz accounts... the hardness ... the mineral.

Ex. 9. Check up if you remember the following:

a) Words of the Greek or Latin origin form their plural by changing the suffixes in the following way:

The following nouns have the same forms of their singular and plural:

apparatus, means, news, series, species

b) Make up singular-plural pairs from the list below: quanta, maximum, analyses, vacua, axis, maxima, nuclei, analysis, apparatus, criteria, nuclcus, quantum, matrix, crisis, theses, crises, moments, axes, syntheses, criterion, thesis, momentum, synthesis, vacuum, matrices,

apparatus

c) Translate the sentences into Uzbek paying attention to the italicized nouns.

1. Until about 1860 the majority of chemists used formulae merely as a convenient representation of organic compounds. 2. We heard a very good news today. 3. The phenomenon of attraction of opposites interested many philosophers. 4. Neutrons are also the most effective means of producing artificial radioactivity. 5. Avogadro’s hypothesis was originally advanced to explain Gay-Lussac’s law of combining volumes. 6 . Ibcrc is some new apparatus on that table. 7. To analyse species is to identify their constituent elements. 8. There are eighteen elements in this series.
Ex. 10. Translate the sentences into Uzbek paying attention to link-verbs.

1. Quartz is a hard, colourlcss substance. 2. Silicic acid is a weak acid. 3. To break a crystal of quartz is to break some silicon-oxygen bonds.4. Silicon mostly occurs combined. 5. As chemistry developed, some hypotheses became laws. 6. An acid turns blue litmus red. 7. Watcr tums into icc at 0°C. 8. Only a few of metals occur free in nature. 9. At boiling point, water turns into vapour. 10. The students remained silent. 11. The hypothesis holds true under different conditions. 12. The solution turns yellow on standing. 13. He felt sorry for what he had done. 14. The predictions proved right. IS. It was S p. m. and the classes were over. 16. Dalton’s atomic theory became one of the foundations of modem chemistry.

Ex. 11. Translate the sentences into English.

1. Kremniy yer yuzidagi eng keng tarqalgan elementlardan biridir.

2. Kremniy asosan kremniy dioksidi shaklida bo'ladi. 3. Kvarts rangsiz qattiq moddadir. 4. Kvartsning qattiqligi uning tuzilishi bilan izohlanadi. 5. Kvartsning tuzilishi Kremniy birikmalarning tuzilishi bilan chambarchas bog'liq. 6. Silikat kislota juda kuchsiz kislotadir, u osonlikcha kondensatsiyalanadi. 7. Kremniy dioksidda kremniy to'rt kislorod atomi bilan o'ralgan va har bir kislorod atomiga vodorod atomi biriktira oladi.
Ex. 12. Make up two or three questions to the italicized parts of the sentences.

1. Quartz crystals are identified as right-handed or left-handed (2).2. The structure of quartz and of other forms of silica is described as consisting o fSi04 tetrahedra (3). 3. In order to break a crystal o f quartz it is necessary to break some silicon-oxygen bonds (2).

Ex. 13. Answer the following questions:

1. In what state does silicon occur? 2. What are the physical properties of quartz? 3. How is the hardness of quartz accounted for? 4. What do you know about silicic acid? 5. Describe the molecular structure of SiOj.