Henry cavendish and his discovery

Henry Cavendish was born in 1731 and died in 1810. He was an English nobleman who did scientific experiments as a hobby, In 1781 he made the important discovery that water is not an element but a compound of the gases we now call hydrogen and oxygen. He described his experi­ments to the Royal Society in 1785.

His method was new. He showed that if electric sparks are passed¹ through a mixture of hydrogen and oxygen the two gases combine explosively^ and form water. This was a dangerous experiment. Cavendish did his expe­riment safely; he wisely used a strong brass container for the gases. He also passed electric sparks through air and found that gases which readily dissolve in water form acids. We explain this reaction today as follows: oxygen and nitrogen combine and form oxides of nitrogen.

Cavendish also noticed that air contained a small proportion of a gas which did not combine with any other gas even if we pass electric sparks through it for a long time. Now we think that this gas was probably argon, one of the inert gases. It was rediscovered many years later.

Memorize the following words and word-combinations:

1. if electric sparks are passed —якщо електричний розряд пропускати

2. explosively — із вибухом

3. nobleman – дворянин

4. discovery – відкриття

5. safely – безпечно

6. wisely – мудро

7. brass container – латунний контейнер

8. dissolve – розчинятися

9. acid – кислота

10. was rediscovered – було відкрито заново

Answer the questions:

1.What was Henry Cavendish?

2.When and where did Cavendish live?

3.What did Cavendish discover?

4.Is water an element?

5.How did Cavendish prove that water is a compound?

TEXT 3

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Great scholar of the renaissance

Galileo Galilei lived at a time of Renaissance, an outstanding period in mankind's history, which at the end of the 16th and the beginning of the 17th century extended in the sphere of the natural sciences. The Renaissance gave the world many courageous fighters for knowledge und new outlook on the world.

Galilei was not only a scientist, professor of physics and mathematics at Pisa University and Padua University, but also a critic of official views in science.

He discovered the basic laws of complex forms of motion. Galilei is famous not only for his establishment ... fundamental conceptions of kinematics and dynamics such as speed and acceleration but also for the establishment of general principles of classical mechanics.

Heal world fame came to Galileo only in 1610 when iip constructed the first telescope in the world. With this instrument he discovered satellites of Jupiter, the phases of Venus and the spots in the Sun. He measured the height of the mountains on the Moon with great accuracy and proved that the Milky Way was not milk split by the Madonna but a gigantic conglomeration of stars. Galileo followed the great Italian philosopher Giordano Bruno, who died at the hands of the Inquisition, and defended the idea of an infinite Universe with multitude of inhabited worlds.

In 1633, as a sick, 70-year-old man Galilei was inter­rogated by the Inquisition, found guilty and was sentenced to spend the rest of his life under the surveillance the Inquisition.

We know Galilei as the founder of the map of the world, a map that is constantly growing and becoming more accurate. We see him as a philosopher who struggled against the dogma of religion, as a real revolutionary in science.

Memorize the following words and word-combinations:

1.Renaissance – Відродження

2.оut standing – видатний

3.mankind – людство

4.extend – розширюватися

5.natural sciences – природничі науки

6.courageous fighters – сміливі борці

7.outlook – погляд

8.law – закон

9.establishment – встановлення

10.speed and acceleration – швидкість і прискорення

Answer the questions:

1. When did Galilei live?

2. What do you know about the Renaissance?

3. What did Galilei discover?

4. What did Galilei see through the telescope?

5.Whom did Galileo follow?

TEXT 4

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THE PERIODIC LAW OF CHEMICAL ELEMENTS

For a long time the possibilities of discovering some regularities in the properties of elements occupied the minds of many scientists all over the world. As a consequence in the middle of the 18th century the French chemist, Lavoisier, for the first time started the quantitative analysis of the then known chemical elements, in this way setting up the corner-stone of the chemical science.

Following his example, other chemists turned their attention to the quantitative analysis too. Among them was an English chemist, John Dalton, who, early in the 19th century, took the first steps towards the establishment of his atomic theory. Having assumed that different elements possess unlike atoms, he started investigating their relative weights Dalton's emphasis on the weights of the atoms was, indeed, his greatest contribution to science, since there was nothing new in the atomic hypothesis itself.

By the middle of the 19th century chemical elements had been clas­sified into two general groups: metals and non-metals. But studying the properties of the elements belonging to each of the two categories, chem­ists arrived at the conclusion that there existed some "borderline" elements possessing the properties of both metals and non-metals. While looking for relations among the properties of elements within metal and non-metal groups, chemists were quick to realise the importance of a new concept called "valence", which expresses the relative capacity of atoms to combine with one another.

When proved experimentally the new concept was universally adopt­ed as a reliable means for classifying the properties of elements. Thus, helped by the valence concept chemists were able to build up a numeri­cal scale of valences of the elements, due to which they revealed an im­portant phenomenon: despite the fact that no two elements were identical some of them did display similarities so strong that they seemed to belong to the same "family".

Thus, using further the valence concept as a guide, scientists succeeded in separating these groups and in exploring the extent of similarity within them. The growing list of elemental families combined with the evidence of atomic weight regularities within them made it possible for the investigators to correlate, systematically, the atomic weights and prop­erties of all the then known elements. An English experimentator, J. New-lands, having compared the atomic weights and properties of the ele­ments, proposed a law, according to which "properties are repeated at equal intervals when the elements are arranged in order of increasing atomic weight". But having anticipated the periodicity of properties, Newlands was unable, however, of systematising the properties of more than a few of the elements.

It was Dmitri Ivanovich Mendeleyev (1834—1907), a Russian scien­tist, professor of St. Petersburg University, who succeeded in building up a workable periodic classification of all the then known elements by

arranging them in a table. The best statement of the Periodic law is that of Mendeleyev himself : "The properties of the elements are in peri­odic dependence upon their atomic weights."

So being based on atomic weights of elements, Mendeleyev's Table correlated the whole chemistry of an element to the weight of its atom. It proved that the properties of the atoms were the source of all the chemi­cal properties of the elements, though it was some thirty years before there was any evidence ^a that the atom was a composite body. In the course of improving⁴ his Table, D. I. Mendeleyev made bold predictions of the properties of yet undiscovered elements for which he left blank spaces.

His predictions of the missing elements were based on the group characters of the families the anticipated elements were to join, on the observed regularity of properties within these families, and on the expect­ed dissimilarities between the neighbouring elements within the periods involved.⁵ In direct consequence the element gallium was discovered in 1875, filling the gap immediately below zinc, scandium — in 1879, filling the gap below calcium, germanium — in 1886, filling the second gap below zinc. By 1900 the Table had become an indispensable part of chemi­cal science. At present all spaces between 1 and 104 are filled. As a trib­ute to the originator of the Periodic law, the 101st element discovered by American scientists in 1951 was named mendeleyevum.

Having won recognition all over the world Mendeleyev's Periodic law is regarded as one of the most important achievements in the history of science. It is invariably referred to in the works of the 20th century investigators dealing with new developments in chemistry, physics, atomic theory and theoretical metallurgy.

Memorize the following words and word-combinations:

1. then known — тоді відомих

2. they seemed to belong to the same "family" – здавалося, вони належали до однієї сім’ї

3. it was some thirty years before there was some evidence — то були докази

3. In the course of improving — в ході доказів

4. within the periods involved — в межах цього періоду

5. properties – властивості

6. atomic theory – теорія атомів

7. relative weight – відносна вага

8. possess – мати

9. exist - існувати

Answer the questions:

1.What occupied the minds of many scientists?

2.Who began the quantitative analysis of the chemical elements?

3.Who was John Dalton?

4.When were the chemical elements classified into two general groups?

5.What is “valence”?

TEXT 5

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