I. Определите, является ли утверждение:

1. The gas flow to the burner can be kept under control manually.

A) ложным

B) в тексте нет информации

C) истинным

2. The heat exchanger is to resist corrosion.

A) в тексте нет информации

B) ложным

C) истинным

3. A thermostat belongs to the heating system.

A) в тексте нет информации

B) ложным

C) истинным

4. Cold water from the radiators returns to the expansion tank.

A) истинным

B) в тексте нет информации

C) ложным

II. Укажите, какой части текста (1, 2, 3, 4) соответствует следующая информация:

1. The heated water can be used in household.

A) 3

B) 4

C) 2

D) 1

2. Pipes provide transferring of heat.

A) 1

B) 4

C) 2

D) 3

3. When the water temperature reaches the right level, the gas control valve shuts off.

A) 2

B) 1

C) 4

D) 3

III. Выберете правильный вариант ответа на вопрос:

In what case is the gas control valve to shut off?

A) It is to shut off when the water starts to boil.

B) It is to shut off when the water reaches the beforehand set temperature.

C) It is to shut off when a thermostat is broken.

D) It is to shut off the water temperature is high.

IV. Определите основную идею текста:

A) The main idea of the text is to show gas central heating is wide-spread heating system.

B) The main idea of the text is to show gas central heating is not a complicated system.

C) The main idea of the text is to show the arrangement of gas heating system.

D) The main idea of the text is to show environmental advantages of gas heating system.

Metal alloys

1. A metal alloy is a metallic substance composed of two or more elements, which keep the same crystal structure in the alloy. Metals are combined with metals and/or with non-metal elements, for example carbon. Metal with metal alloys are made by mixing the molten substances and then cooling them until they solidify. Common alloys are brass (copper + zinc) and aluminum alloys (aluminum + copper, aluminum + magnesium), and steel. Plain carbon steel contains only iron and carbon, while alloyed steels, e.g. stainless steel, contain chromium as the main alloying element.

2. Alloy systems are classified either according to the base metal, i.e. the metal serving as base of the alloy, or according to some specific characteristic that a group of alloys share. Depending on their composition, metal alloys are often grouped into two classes: ferrous and non-ferrous alloys.

3. The principle constituent of ferrous alloys is iron as in, e.g. steel and cast iron. They are produced in larger quantities than any other metal type, being especially important as construction materials. Iron and steel alloys can be produced using relatively economical techniques to be extracted, refined, alloyed and fabricated. Ferrous alloys have a wide range of physical and mechanical properties. However, they have relatively high density, which means they weigh a lot; their electrical conductivity is comparatively low and they are susceptible to corrosion in some common environments.

4. Since nonferrous alloys have distinct limitations, other alloy systems are used for many applications, e.g. copper, aluminum, magnesium, titanium alloys, super alloys, the noble metals, and other alloys, including those that have nickel, lead, tin, zirconium and zinc as base metals.