Properties of metals

Task 1. What properties of metals do you know?

Task 2. Make a list of the most important metal properties, then compare it with your partner.

3. Match the notions with their meanings:

1.	hardness	a)	property that gives an opportunity electricity or heat to travel through or along the material
2.	density	b)	an exact amount of a material
3.	conductivity	c)	the relationship between the mass of something and its size
4.	weight	d)	such material is stiff and will not bend

The uses of metals are based upon their physical or chemical properties. Metals vary in density, hardness, heat conductivity, electrical conductivity and weight. The metals resemble one another in their general chemical behaviour with other substances, but they differ markedly in activity.

In considering the chemical properties of metals, the first point which must be mentioned is that they vary widely in degree of chemical activity: some are enormously active and others very inert. In general, metals are chemically combined with one or more other elements and the compounds are known as ores.

The metals vary greatly in density. The lightest is lithium, which has the density of 0.534 and is, therefore, about one-half as heavy as water. The heaviest is osmium (3D. 22.48) which is closely related to platinum (D. 21.45) in physical and chemical properties. The so-called light metals, of which sodium, potassium, magnesium and aluminium are examples, have a density less than 4; iron, lead, tin, silver, etc. are known as heavy metals.

The metals also vary in hardness, from potassium, which can be molded like wax, to chromium, which will cut glass. The metals and other substances differ in the extent to which they can resist a strain that tends to bring about a permanent change in their form. Hardness is the property to resist deformation under applied load. Hardness is the most important mechanical property of metals. The hardness of metals depends upon the presence of other substances in them and the nature of metal itself.

All substances offer more or less resistance to the flow of an electric current through them. With any given substance, the resistance is determined by its dimensions and the temperature. Metals are the best conductors of heat and electricity.

Task 4. Give English equivalents to the following words and word combinations:

густина, теплопровідність, бути схожим, ступінь хімічної активності, руда, вдвічі легший за воду, легкі та важкі метали, різнитися, твердість, різати скло, чинити опір деформації, наявність інших речовин, електрострум, найкращі провідники тепла та електроенергії, формувати, призводити до, залежати від, визначатись.

Task 5. Translate and memorise the names of some metal properties:

Density, hardness, heat conductivity, electrical conductivity, weight.

Task 6. Find in the text antonyms to the following words:

softness, narrowly, passive, unknown, the lightest, heavy, more, temporary, above, least, the best.

Task 7. Make up word combinations from the following words:

chemical	current
applied	conductivity
chemical	conductors
light	properties
electric	change
electrical	behaviour
best	metals
permanent	load

Task 8. Put the adjectives in brackets into the proper degree of comparison:

1. Lithium is (light) metal and has the density of 0.534.

2. Osmium is (heavy) than platinum.

3. Copper is (good) conductor.

4. Chromium is (hard) metal, it can even cut glass.

5. Because of its physical properties cast iron is (important) for engineers than aluminium.

6. Knowledge of physical properties of metals is one of (important) skill of (good) engineer.

Task 9. Answer the following questions:

1. What are the uses of metals based upon?

2. What do the metals vary in?

3. Do metals vary in degree of chemical activity? How do they vary?

4. What light metals and heavy metals do you know?

5. Is osmium the lightest or the heaviest metal?

6. What is the most important mechanical property of metals?

7. Are all metals the conductors of electricity?

8. What is the resistance determined by?

Task 10. Memorize the following words and word combinations:

1.	applied load	прикладене навантаження
2.	chemical behaviour	хімічна поведінка
3.	degree of chemical activity	ступінь хімічної активності
4.	density	густина
5.	to determine	визначати, встановлювати
6.	dimension	розмір, об’єм
7.	electrical conductivity	електропровідність
8.	enormously	надто, надмірно
9.	glass	скло
10.	hardness	твердість, жорсткість
11.	heat conductivity	теплопровідність
12.	heavy metals	важкі метали
13.	inert	інертний
14.	light metals	легкі метали
15.	to mention	згадувати, посилатися
16.	to mold	формувати, робити по шаблону
17.	one-half	половина
18.	physical properties	фізичні властивості
19.	to relate	мати відношення, бути зв’язаним
20.	to resemble	походити, мати схожість
21.	to resist	чинити опір
22.	strain	напруження, деформація
23.	to vary	різнитися, змінюватись
24.	wax	віск
25.	weight	вага

UNIT 4