II. Reading Activity and Speech Practice. II.1 Try to answer these questions before you read the text. What are metals?

II.1 Try to answer these questions before you read the text.

1. What are metals?
2. Do metals very greatly from each other?
3. Properties of metals depend on their crystalline structure, don’t they?
4. What are the two main groups of metals?
5. Where are different metals used?
6. Which metals are mostly used in machine-building to your mind?

II.2 Read the text and check your answers. Translate the text into Russian.

Text A: Metals

Metals are materials most widely used in industry because of their properties. The study of the production and properties of metals is known as metallurgy.

The separation between the atoms is small, so most metals are dense. The atoms are arranged regularly and can slide over each other. That is why metals are malleable (can be deformed and bend without fracture) and ductile (can be drawn into wire). Metals vary greatly in their properties. For example, lead is soft and can be bent by hand, while iron can only be worked by hammering at red heat.

The regular arrangement of atoms in metals gives them a crystalline structure. Irregular crystals are called grains. The properties of the metals depend on the size, shape, orientation, and composition of these grains. In general, a metal with small grains will be harder and stronger one with coarse grains.

All chemical elements are divided into metals and non-metals. They are widely used in making tools, instruments, and devices. Metals and non-metals have different properties.

Copper, cast iron, aluminium are examples of metals. Rubber, plastic and ceramics are examples of non-metals. Today different metals are widely used in machine-building industry.

We can divide all metals into ferrous and non-ferrous. Steel and cast iron are in the group of ferrous metals. They are alloys of iron with carbon, manganese, silicon and other components.

Non-ferrous metals are metals and alloys the main component of which is not iron but some other elements such as aluminium, copper and others. Some of the characteristics of nonferrous metals are high electric and heat conductivity, high corrosion resistance, light weight and easiness of fabrication.

The combination of metals and non-metals is known as an alloy. For example, steel is an alloy of carbon and iron. The alloy of copper and zinc is known as brass. The properties of alloys are often better than the properties of their constituents. That is why the majority of engineering products are made of various alloys.

I.3 Answer the questions given before the text.

II.4 Say whether you agree or disagree with these statements.

1. All engineering materials are divided into metals and non-metals.

1. Copper, cast iron, aluminium are examples of non-metals.
2. Today different metals are widely used in machine-building industry.
3. Steel and cast iron are in the group of ferrous metals.
4. Non-ferrous metals are metals and alloys the main component of which is not iron.
5. Some of the characteristics of non-ferrous metals are high electric and heat conductivity.
6. Rubber, plastic and ceramics are examples of non-metals.

II.5 Find the sentences to describe:

· metallurgy as a science;

· interdependence between metal properties and their crystalline structure;

· ferrous metals;

· non-ferrous metals;

· the use of different metals.

II.6 Make a plan to the text to speak about metals and their properties and the main kinds of metals.

II.7 Give answers to the given questions and reproduce the dialogue with your partner.

- There are two kinds of engineering materials, aren’t they?

- …..

- What are they?

- ….

- Can you give any examples of non-metals?

- Sure. ….

- Are engineering materials widely used?

- Certainly. ….

Дата добавления: 2015-10-30