Text. Heat

What is heat? There have been many theories to explain the nature of heat. About a century ago heat was considered to be an invisible substance that passed from a hot to a cold object. This supposed substance was called caloric.

According to the caloric theory, when an object was heated in a flame it became full of caloric. The object would transfer part of its caloric to a colder substance when placed next to it. Only Robert Boyle and Isaac Newton began to think about heat in terms of molecular motion. Our great scientist M. V. Lomoriosov was among the first to state that heat phenomena were due to the motion of molecules. That statement of his was the result of many carefully per­formed laboratory experiments, of study and observations. Lomoriosov's theory laid the foundation for the present-day molecular-kinetic theory of heat.

Today heat is known to be a form of energy. The coal that burns in a boiler vaporizes the water and speeds up the steam molecules. The molecules of steam bombard the pis­tons in the cylinders of the locomotive so that a heavy train can be hauled across a continent. The chemical energy of coal is transformed into heat energy of the molecules of steam. The motion of the steam molecules is transformed to the motion of wheels by which the train is moved.

Listen and read words and word combinations to be re­membered:

explain [iks'plein] объяснять invisible [in'vizəbl] невидимый

suppose [sə'роuz] предполагать flame [fleim] пламя

transfer ['trænsfə:] передавать due to ['dju: tu] благодаря

perform [pə'fo:m] выполнять burn [bə:n] гореть

vaporize [veipəraiz] выпаривать haul [ho:l ] тащить

speed up [spi:d ap] ускорять steamn [sti:m] пap

piston ['pistən] поршень

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Models

1. Heat is known to be a form of energy.

He is known to be a good student. The students are said to have passed their exams well. The book is considered to be very interesting.

2. You place, you placed, you have placed. They take, they took, they have taken.

3. Newton began to think about heat.

He began to read about nature. They began to think about their work. She began to prepare for her exams early in the term.

4. He was the first to state ... .

He was the first to have known this news. We were the first to come back. She is the first to have read this book.

Exercises

1. Listen, read and translate the text.

2. Answer the following questions in a written form:

1. Who began to think about heat in terms of molecular motion? 2. What did Lornonosov's theory lay the founda­tion for? 3. What is heat known to be today? 4. Which Lomonosov's statement was the result of many carefully per­formed laboratory experiments?

3. Make up and write 8 sentences using the words given in the table:

Experiments They Our students Heat The molecules of steam

are known was consid­ered were said

to be an invisible substance. to be performed in the laboratory. to study well. to have seen all new films. to bombard the pistons in the cylinder.

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4. Translate the following sentences and explain the use of tenses in them:

1. Heat can never be produced without the expenditure of some other form of energy. 2. Because of this we regard heat itself as a form of energy. 3. When a lump of lead is vigorously hammered, it becomes hot—mechanical energy is changed to heat. 4. If coal gas is burned, chemical energy is changed to heat. 5. An electric current passing through the element of an electric fire produces Heat from electrical energy. 6. On a fine summer's day the radiant energy cross­ing the 93 million miles of space from the sun warms us as we bask in its rays. 7. So long as the lead is hammered, fuel used, electric current passed and so on, heat energy ap­pears.

5. Make up and write 8 questions using the words given in the table

:

Who What

was the first is known bombards began is transformed

to state this phenomenon? to think about heat? into heat energy? to be a form of energy? to the motion of wheels? the piston in the cylinder?

6. Make up and write all possible questions to the follow­ing sentences:

1. We regard heat as a form of energy. 2. We must indi­cate temperature in numerical terms. 3. The Celsius scale was devised by Celsius in 1742.

7. Copy these sentences putting "invisible", "heat", "calor­ic", "hauls", "performs", "speed up" in the blanks:

1. An object heated in a flame became full of .... 2. They thought about ... in terms of molecular motion. 3. Heat was considered to be an ... substance. 4. The locomotive ... a heavy train. 5. He ... some experiments. 6. They ... the process of transformation.

8. Find English equivalents to the following word combina­tions:

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природа тепла, столетие тому назад, невидимое ве­щество, молекулярное движение, тепловое явление, благо­даря, тщательно выполненный, заложил фундамент, совре­менная молекулярно-кинетическая теория, тепловая энер­гия.