Thickness, rare, equipment, account, spark, least, similar, deposit

1. Palladium is the … dense of the platinum group metals.

2. A black … on the surface of silver is silver sulfide.

3. Platinum has found wide application in various kinds of ….

4. Platinum is used in electrical contacts because it cannot be melted by the heat of a ….

5. The … of a gold sheet may be very small.

6. Silver is … to gold in many ways.

7. Palladium is a …, lustrous silvery-white metal.

8. High electrical conductivity and high corrosion-resistant qualities of copper … for its wide use in industry.

Agree or disagree with the following statements. Prove your reason. Use the expressions: I’ll certainly agree with it because…, I certainly won’t agree with it because ….

1. Platinum is only used for making ornaments.

2. Gold is very ductile.

3. Gold is the most chemically active of all metals.

4. Only pure gold is used in jewelry.

5. Silver is more reactive than gold.

6. Silver does not conduct electric current.

7. The proportion of gold in an alloy is measured in grams.

8. The platinum group metals are widely used.

1. Translate the text in writing. Use a dictionary. Find answers to the questions:

What metals are known as noble?

What is meant by "galvanic series"?

Noble metals

Noble metals are metals that are resistant to corrosion and oxidation in moist air, unlike most base metals. They tend to be precious, often due to their rarity in the Earth's crust. The noble metals are considered to be (in order of increasing atomic number) ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, gold.

Other sources include mercury or even rhenium as a noble metal. On the other hand, neither titanium nor niobium nor tantalum are called noble metals despite the fact that they are very resistant to corrosion.

Noble metals should not be confused with precious metals (although many noble metals are precious).

Sometimes, nickel and zinc are noble metals, because copper coins usually use nickel and zinc together with copper.

Palladium, osmium, platinum, gold and mercury can be dissolved in aqua regia, a highly concentrated mixture of hydrochloric acid and nitric acid, but iridium and silver cannot. Ruthenium can be dissolved in aqua regia only when in the presence of oxygen, while rhodium must be in a fine pulverized form. Niobium and tantalum are resistant to acids, including aqua regia.

Th term "noble" can also be used in a relative sense, considering "noble" as an adjective for the word "metal". A "galvanic series" is a hierarchy of metals (or other electrically conductive materials, including composites and semimetals) that runs from noble to active, and allows designers to see at a glance how materials will interact in the environment used to generate the series. In this sense of the word, graphite is more noble than silver and the relative nobility of many materials is highly dependent upon context, as for aluminum and stainless steel in conditions of varying PH.

Unit 15

1. Memorize the following words:

sealing origin a number of resin raw material by-product available thermosetting cloth translucent rubber source gum exudation stable impermeable abrasive finish artificial

уплотнение начало, происхождение несколько, ряд смола,полимер сырье побочный продукт доступный термореактивный ткань полупрозрачный резина источник смола, каучук выделение устойчивый непроницфемый, плотный абразивный отделывать искусственный

ущільнювання початок, походження декілька, ряд смола, полімер сировина побічний продукт доступний інтенсивний тканина напівпрозорий гума джерело смола, каучук відокремлення стійкий непроникний, щільний абразивний опоряджати штучний

1. Practise the reading of the following words:

purpose, lining, sealing, binding, valuable, inorganic, resinlike, synthetic, polymer, molecular, raw, available, constructural, fluoroplastics, translucent, decorative, automotive, quartz, artificial, impermeable, exudation, diamond, asbestos.