3. Match the English words and word combinations given below with the Russian equivalents

1. the largest amount а) однородная смесь

2. the chemical composition b) два жидких слоя

3. the physical properties с) сравнительно редко

4. more expensive d) наибольшее количество

5. comparatively seldom e) из жидкого состояния в твердое

6. formed by the solidification f) химический состав

7. a homogeneous mixture g) физические свойства

8. two liquid layers h) более дорогой

9. from the liquid to the solid state i) образованный путем затвер-

девания

4. Answer the following questions

. I. What elements are considered to be non-metallic?

2. What elements exhibit the characteristics of non-metals and what are they called?

3. What does the commercial importance of metals lie in?

4. What two groups are metals usually divided into? What do they differ in?

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5. What is the definition of an alloy?

6. What kind of alloys may there be?

7. What is the necessary condition for metals to form an alloy?

8. What is very important in determining the properties of an alloy?

5. Translate at sight and compare

Physical properties of metals and поп- metals Chemical properties of metals and поп- metals

The 105 elements do not, fortunately, exhibit 105 completely different sets of properties. When the major properties are considered it is found that the elements fall into one or two groups, the metals or the non-metals. The contrast between the properties of these two groups is given below. It is not to be expected that all elements in one class will agree in every detail; some differ in one or two properties from the oth­ers of their class; these exceptions are indicated in brackets.

Physical properties Metals Non-metals

1. Solid at room temperature I. Many are liquids and gases at (mercury the only liquid metal) room temperature

2. Have a high density (expert 2. Density is usually low

potassium and sodium)

3. Can be mounded by pressure, 3. Solid non-metals are britte i.e. they are malleable

4. Have high melting points and 4. Have low melting points and boiling points boiling points

5. Are good conductors of heat 5. Are poor conductors of heat and and electricity electricity (graphite is the only

good conductor of electricity)

6. Can be drawn into a wire, 6. Cannot be drawn into a wire i.e. they are ductile

Chemical properties

Metals Non-metals

1. Have acidic oxides 1. Have acidic oxides

2. React with dilute acids form- 2. Salts of non-metals do not exist ing salts

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3. Form positive ions 3. Form negative ions

4. Are liberated at the cathode 4. Are liberated at the anode during

electrolysis (hydrogen during electrolysis acts as a metal)

Unit 5