Lesson twelve Text: Boilers

I. Read and translate:

If we heat some water in an open glass container, we can see that evaporation goes on from the top surface. This evaporation is indicated by the clouds forming where vapour mixes with the colder air and condenses. We find that temperature of water gradually rises until the thermometer registers 100’C.

A little before, bubbles appear on the sides of the container. They consist partly of gases driven from liquid and partly of water-vapour, for evaporation is directed into the bubbles. Water boils when vapour is formed both at the bottom of the container and at the top of it. The motion of the boiling water is caused by the bubbles of vapour rising through the water. The temperature is known as the boiling point of the liquid.

The boiling point of a liquid is the temperature at which it boils under some given pressure. When this point has been reached, further heating does not increase the temperature of the liquid, but only changes it to steam.

When water boils in a container we say that we see steam coming out of it. In fact what we see is not steam at all but fine water particles. Steam itself is invisible. It is the condensed steam in the form of fine particles of water that we see.

As liquids always increase in volume when passing into the state of vapour, an increase in pressure always produces an increase in the boiling point.

Just as solids may under certain conditions be cooled below their melting points without freezing, so liquids may be heated above their boiling points without boiling.

evaporation surface to form vapour to mix with pressure steam to boil

испарение поверхность образовывать пар смешивать с давление пар кипеть

increase to freeze to cool motion to cause bubbles to reach particle

увеличение замерзать охлаждать(ся) движение причинять, вызывать, провоцировать пузырьки достигать частица

II. Answer the questions:

1. When does water boil? 2. What is the boiling point of the liquid? 3. Is steam visible? 4. Where is vapour formed when water boils? 5. Can liquids be heated without boiling?

III. Find equivalents in the text:

Градусник регистрирует; форме маленьких частичек воды; увеличение давления; дальнейшее нагревание; вверху сосуда; эта температура известна как; пузырьки появляются на стенках сосуда; температура постоянно увеличивается; считается что; под определённым давление;, облака образующиеся; пар смешивается с холодным воздухом и конденсируется; испарение проявляется; до того как; и внизу и вверху.

IV. Find the odd word in each line and explain why:

1. a) vapour, b) steam, c)motion, d) evaporation;

2. a) molecules, b) particles, c) solids, d) body;

3. a) volume, b) motion, c) movement, d) travelling;

4. a) to see, b) visible, c) to reach, d) invisible;

5. a) to rise, b) to register, c) to increase, d) to reach;

6. a) container, b) boiler, c) glass, d) air;

7. a) bubbles, b) bottom, c) top, d) middle;

V. Translate into English:

1. Температура кипящей воды постоянна. 2. Когда мы нагреваем жидкость, её температура постоянно увеличивается. 3. Мы не видим пар, мы видим маленькие частички воды. 4. Когда кипит вода в сосуде, мы можем видеть выходящий из него пар. 5. Когда достигается точка кипения, дальнейшее нагревание не увеличивает температуру жидкости.

VI. Find out a little about: