3 Part One. The Predicate

Section III
Ex. 1. Check up if you remember the ways of expressing time.




Ex. 2. Answer the following questions, using expressions from exercise 1:

1. What time is it now? 2. When do your classes usually begin? 3. When did the lecture begin? 4 .1 believe my watch is fast, what time is it by your watch? 5. At what time shall we meet? 6. At what time are your classes over? 7. When do you get up? 8. When will you be free? 9. When will you come to the laboratory?

Ex. 3. Make up sentences or short stories with the following words:

1) introduce, they, symbols, Swedish, begin, shorthand, chemist, simple, Berzelius, element, name; 2) phenomenon, allotropy, such, be, when, can, form, element, exist, different, the same, state, physical; 3) act, formula, law, the very, write, assume, composition, constant; 4) gram, weight, molecular, be, element, seem, atomic

Ex. 4. Give detailed answers to the following questions:

1. In what way were the modem symbols for the elements introduced?

2. What is the meaning of a chemical symbol for an element? 3. In what way do we usually write formulae for compounds? 4. What law is the basis for writing the formula of a compound? 5. What is an atom? 6. What is a molecule?

Ex. 5. Discuss the following topics:

1. The History of the Introduction of Symbols.

2. Symbols for Representing Elements.

3. Symbols for Representing Compounds.
DO YOU KNOW THAT...

Berzelius published his first paper on the new nomenclature in 1813. A year later, he published his second article in which he formulated the rales for writing formulae. The number of atoms was marked by a figure at the upper end of the symbol. If a compound contained two atoms of a particular element, he suggested that the sign should be written in bold type. He marked an oxygen atom in oxides by a point or a comma. Thus, the formula for water was H⁺ instead of H₂O. New symbols for chemical elements were soon accepted by scientists, they proved very convenient, but as to formulae, they were accepted only in the middle of the 19th century.