EXERCISES. 2. Find English equivalents

1. Find Ukrainian equivalents:

1. essential part а. хімічно чистий

2. all over again b. мінеральна речовина

3. chemically pure c. електрична іскра

4. mineral substance d. все спочатку

5. an electric spark e. суттєва роль

2. Find English equivalents:

1. безколірна рідина а. dissolved gases

2. пропускати іскру b. to pass a spark

3. чиста вода c. mobile liquid

4. рухома рідина d. pure water

5. розчинні гази e. colourless liquid

SOLIDS

Solids are usually described as hard, at least compared with liquids, and as having a definite shape. A powder does not appear to have a definite shape; we can make it into a pointed heap or a flat heap, but in a heap of powder we are looking at quantities of grains each of which has a definite shape. On examining a little piece of common salt under a microscope it will be seen to consist of tiny cubes, some of them damaged, but there will be some perfect ones.

All these substances having a fixed shape are called crystals. Thus we can say that a solid is a crystalline substance. It is not always easy to see the crystals, even through a microscope and at one time it was thought that a powder such as chalk was amorphous, a word which means without shape. However, we now know that chalk is a crystalline substance and even metals are made of exceedingly tiny crystals packed very close together. Now, we know that a crystal of common salt is composed of millions of sodium ions and chlorine ions holding together by electrical attraction, and since chemists have been able to "look" inside a very tiny crystal by means of X-rays, it has been discovered that sodium and chlorine ions are always arranged in a very regular pattern in relation to one another.