2. Give synonyms:

quantity, to call, several, to approach, some, to reach, various, to show, to name, different, to indicate, shape, form, characteristic, number, property, to use, value, generally, ordinarily, to apply, amount.

3. Translate the following sentences:

1. Since a little piece of salt has been examined under a microscope, it was established that it consisted of tiny cubes. 2. Many experiments with different solids were carried out in Middle Ages, since then a great many experimental methods have been developed. 3. Radioactivity is a natural process that has been investigated since the end of the last century. 4. The sum of the charges of proton and electron is equal to that of neutron. 5. The free energy of the reactants is equal to that of the products obtained. 6. Common salt consists of tiny cubes, some of them being perfect ones. 7. A mechanical method was followed by an electrical one. 8. The behaviour of aluminium is similar to that of zinc. 9. The values of the boiling-points are those carefully determined by us, and those of the molecular volumes have been taken from Lassen's data.

Acids and bases

We know acids and bases to be extremely useful1 substances and we have much information about their properties. However, the behavior of these compounds can be explained by several slightly different theories, and some definitions differ somewhat from other definitions.

Acids are compounds which contain hydrogen; most acids containing oxygen. In water solution, they yield H+ ions which are loosely attached to water molecules as oxonium ions. The properties which are common to all water solutions of acids are due to the hydronium ion. All acids contain replaceable hydrogen, have sour taste, neutralize bases, conduct electricity and turn blue litmus red.

An acid can be produced by heating a salt of the acid with sulphuric acid or by the reaction of water with acid anhydrides. Acid anhydrides are non-metallic oxides in terms of their ability to combine with water and to form acids.

One of the most important acids, the hydrochloric acid, is known to be formed by dissolving hydrogen chloride in water. Some other important acids are sulphuric acid, nitric acid and acetic acid.

Bases are hydroxides of metals. They are the chemical opposites of acids. Most bases are electrovalent compounds which dissociate into ions by the action of the solvent water. Among the more important bases arc sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonium hydroxide.

The properties common to all water solutions of bases have a bitter taste, feel soapy, neutralize acids, conduct electricity, and turn red litmus blue.

Bases may be made by adding an active metal to water, by combining a metal oxide with water, or by combining a salt with a soluble base.

NOTES

1. Extremely useful – надзвичайно корисні

2. Are common to all – загальні для всіх

3. Acetic acid - оцтова кислота