Завдання 2. Доповніть речення згідно зі змістом тексту

1. The conductor has equal numbers of________________.

2. The nucleus consist of_________________.

3. The atoms in metals__________________.

4. The battery causes a potential difference between_______________.

5. Obviously materials differs________________________.

Завдання 3. Знайдіть у тексті синоніми та антоніми до наступних слів.

Завдання4. Виберіть речення, які відповідають змісту тексту.

1. The atom is made up of a negative nucleus.

2. The conductor has equal numbers of positive and negative charges in its atom.

3. The current will flow unless there is an electric circuit.

4. In the modern conception matter is composed of atoms.

5. A negatively charged body contains equal numbers of electrons and protons.

Завдання 5. Складіть речення з поданих слів.

1. the positive electrode, is, flow, the electric current, the electron, toward

2. consists of, neutrons, the nucleus, one as more

3. made up, a positive nucleus, is, the atom, of

4. to know, can be made, we, to produce, how, want, the, charges, a current

5. in, overlap, to some, the atoms, metals, extent

UNIT 7

PROPERTIES OF METALS.

Metals resemble one another in their general chemical behaviour, but they differ greatly in activity.

The uses of metals are based upon their physical and chemical properties. 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 (D. 22.48) which is closely related to platinum (D. 21.45) in physical and chemical properties. The so-called light metals, as for example sodium, potassium, magnesium and aluminium, have a density less than 4; iron, lead, tin, silver, etc. are known as heavy metals.

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 by how much they can resist a strain that tends to bring about a permanent change in their form. All substances offer more or less resistance to the flow of an electric current through them. For any given substance, the resistance is determined by its dimensions and the temperature.

The solids obtained when two or more metals are mixed in the molten condition and allowed to solidify are called alloys. Each constituent of an alloy is called a component. Alloys may be binary (two-component), ternary (three-component), etc. The ability of various metals to form alloys differs greatly.

Завдання 1. Дайте відповіді на запитання.

1. What metal is the heaviest?

2. What metal is the lightest?

3. What is an alloy?

4. To what group of metals does aluminium belong?

5. What are the main characteristic features of metals?

Завдання 2. Доповніть речення згідно зі змістом тексту.

1. The uses of metals are based …..

2. Metals vary greatly in …..

3. Each constituent of an alloy is …..

4. The ability of various metals …..

5. For any given substance, the resistance is ………

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