Exercise 9. Read and make a summary of the text.

ELEMENTS, COMPOUNDS, MIXTURES AND COMPOSITES

Taking into consideration the chemical composition of materials, that is the chemicals they contain, and how the chemicals are combined, we may distinguish the following main categories of materials: elements, compounds, mixtures and composites.

Pure materials in their basic form are called elements. They cannot be broken into separate constituents. The most common elements widely used in engineering are iron, aluminium and carbon.

Materials which consist of two or more elements combined by chemical reaction present a category of compounds. An everyday example is water – a compound of hydrogen and oxygen.

Mixtures include two or more elements or compounds which are mixed together but are not chemically bound. The most common mixtures used in engineering are alloys. Steel, an iron-carbon alloy, can include in small quantities other elements such as chromium, manganese and tungsten.

A composite material is a matrix with a reinforced material inside it. Fiberglass, correctly called glass-reinforced plastic, is a composite with a plastic matrix reinforced with fiberglass. Composite materials are considered to be hi-tech materials.

Exercise 10. Compile information about engineering materials and participate in a project. Give reasons why this or that material is widely used in machine building industry. You may use the following web site: www.materialmoments.org/top100.html

TEST 3

1. Choose the proper words and fill in the blanks.

1. Materials which consist of two or more elements combined by chemical reaction present a category of … .

A elements B compounds C mixtures D composite materials

2. … is a matrix with a reinforced material inside it.

A An element B A compound C A mixture D A composite material

3. … includes two or more elements which are not chemically bound.

A An element B A compound C A mixture D A composite material

4. … cannot be broken into separate constituents.

A An element B A compound C A mixture D A composite material

5. Cast iron and steel are … .

A elements B compounds C mixtures D composite materials

6. Copper is … .

A an element B a compound C a mixture D a composite material

7. Polymers are representatives of … .

A ceramics B plastics C non-metallic materials D thermosets

8. … polymers are usually called ‘plastics’.

A Natural B Synthetic C Cheap D Non-rusting

9. Ceramics are … .

A ductile B stiff C malleable D lightweight

10. A lot of engineering materials are … to engineer.

A flexible B brittle C available D subsequent

2. Fill in the blanks with the proper forms of the Verbals.

1. … rather brittle this material is not widely used.

A Been B Being C Have been D Has been

2. … this experiment the engineers should have two types of thermoplastics.

A Made B Makes C Make D To make

3. The technological process of … this material was changed during the experiment.

A producing B to produce C produce D produced

4. This problem is … by the engineers.

A to research B researching C researched D research

5. The materials … in the production of these tools are alloys.

A to use B using C to be used D to have used

6. While … ceramics they changed the technological process.

A form B to form C forming D to be formed

7. Modern technologies have made it possible … new materials.

A to produce B to be produced C produce D to have been produced

8. Stainless steels … nickel or chromium do not rust.

A contain B contains C have contained D containing

9. The most widely … non-ferrous metals are aluminium and copper.

A to use B use C used D using

10. One of the best … natural polymers is rubber.

A know B known C to know D to be known