The famous scientists

Lead-in

· Why do people choose to become scientists?

· What scientists do you admire?

· What are the most well-known chemists? What are they famous for?

· Who are the most influential scientists nowadays? Why?

Pronunciation tips

1.	cholera	[ˈkɑlərə]		isomorphism	[ˌaɪsəˈmɔrˌfɪzəm]
2.	diphtheria	[dɪfˈθɪriːə]		pasteurization	[ˌpæstʃərəˈzeɪʃən]
3.	disease	[dɪˈziːz]		rabies	[ˈreɪbiːz]
4.	germ	[ˈdʒərm]	8.	vaccine	[vækˈsiːn]

THE FAMOUS SCIENTISTS

Dmitri Ivanovich Mendeleev was primarily a chemist even though he later worked in many other fields. One of his most important contributions to chemistry was the discovery in 1869 of the periodic law of the chemical elements, which is still a fundamental concept in modern chemistry. In 1905, shortly before his death, he listed what he considered his four main contributions to science: the periodic law, the elasticity of gas, the understanding of solutions as associations, and The Principles of Chemistry.

Mendeleev entered the Main Pedagogical Institute at St. Petersburg in 1850 after graduating from the gymnasium in the Siberian city of Tobol’sk, where he was born in 1834. While a student, he published his first scientific papers on the chemical analysis of minerals. His undergraduate thesis was on isomorphism and was concerned with the development of mineral analysis.

Mendeleev’s concept of the chemical elements as a stable, intermediate level of matter, not necessarily based on the speculative concept of the atom, corresponded to the state of chemistry in the mid-19th century. Ironically, it helped him discover the periodic law. As a result of his discovery, the concept of an element gained another positive characteristic in its definition: an element occupies a specific place in the periodic system. Later Mendeleev’s concept of chemical elements developed into ‘chemical individuals’, his further attempt to avoid the speculative connotations of the atomic theory. Even though the formats of Mendeleev’s textbook changed substantially with each edition, his firm belief in the validity of the concept of the chemical elements remained unchanged from the 1860s.

Dmitri Mendeleev	Louis Pasteur
(8 February 1834 – 2 February 1907)	(27 December 1822 – 28 September 1895)

Louis Pasteur was a famous chemist and biologist. He proved that germs cause many diseases. He invented ways to kill harmful germs in milk and other products. Pasteur also developed a vaccine to prevent rabies. His work greatly helped to control disease in both people and animals.

Pasteur performed many experiments to understand why beer and wine sometimes soured. He found that microbes, or germs, from the outside caused spoiling. This led him to believe that the same process caused many diseases. According to the germ theory, infectious diseases are the result of germs from the outside attacking the body.

During Pasteur’s time, the souring of beer and wine caused major losses of money for producers in France. Pasteur and others found that heating the starting sugar solutions to high temperatures eliminated enough of the bacteria to prevent spoilage. He then applied the idea to other products such as milk, cheese, and other food products. The products are sufficiently heated under pressure to kill harmful bacteria and reduce spoilage. Bearing the name of the inventor, the process of ‘pasteurization’ is widely used throughout the world today.

Pasteur spent a lot of time studying the cause of many diseases. He developed vaccines to prevent them where possible. Although he worked on cholera, diphtheria, tuberculosis, and smallpox, he is perhaps best known for his work on rabies.