Chemistry is a great and complex subject. It is a of substances, their properties(пропртииз) and the reactions that change them into other substances
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- 12.13.14.17. Mendeleyevs Periodic Law
| 9.10. 19.My first experiment
Last week our group conducted (kənˈdəktəd) a very interesting experiment on chemistry. We obtained pure (пиё) hydrogen at our last lesion. For conducting an experiment we needed different apparatus (ˌapəˈradəs). We used various glassware or dish such as test – tubes, bottles, flasks, funnels, beakers, glasses, rods and tubes. Before the reaction the students weighed (уэдт) substances on the scales, We needed some metals and acids (аэседс). Then we put some metallic zinc into the round - bottom flask and began to add some drops of hydrochloric (хайджер клорект) acid. Then we put a burning match at the top of the flask. We saw a blue flame that was a fact that we obtained pure hydrogen or inflammable air. We observed the reaction and recorded the yield. At the end of the reaction we washed all dishes and put them on proper places. 12.13.14.17. Mendeleyev's Periodic Law The Periodic Law discovered by D. I. Mendeleyev in 1869. Mendeleyev arranged(эрейінж) the elements in tabular form in such (саш) a way as to bring their correspondences(коресспонденсез) quite clearly(клерли). The elements are divided(девайдет) into eight groups, each of which is entered in a separate column(соупрейт колон). They are also divided into 10 «series» each of which is entered upon one horizontal line. The atomic weights increase across the table from left to the right. D. I. Mendeleyev was the first to discover the law of dependence of the properties of the elements upon their atomic weights. The elements in any one column are similar to one another in many ways, the resemblance being very striking. Mendeleyev found it impossible to construct his table without leaving many of the spaces in it vacant. He considered these vacancies to correspond the elements which were not then known, but which would probably be discovered in the future. Today the Periodic Law is studied by millions of secondary schoolchildren and by the students at higher establishments of natural sciences and engineering. It is studied by philosophers, historians and teachers. The Periodic Law serves as a platform for thousands of researches. жүктеу/скачать 22 Kb. Достарыңызбен бөлісу:
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