Exercises

1. Answer the questions

1. How can the movement of molecules be studied?

2. Why does gas have neither definite shape nor volume?

3. Why is liquid slightly compressible?

4. Why is the freedom of molecules in solids very restricted?

5. Why is it very difficult to compress a solid?

6. In what substances do chemical changes occur most readily?

2. Give English equivalents:

1. потужний мікроскоп а. under observation

2. постійний рух b. independent existence

3. під наглядом c. high speed

4. незалежне існування d. continual movement

5. велика швидкість e. powerful microscope

3. Give Ukrainian equivalents:

1. with each other а. сила тяжіння

2. to exert pressure b. змінювати об’єм

3. the attractive force c. постійна форма

4. to vary one's volume d. чинити тиск

5. a fixed shape e. один з одним

4. Translate the sentences:

1. Matter is constantly undergoing changes. 2. The concept of matter is intuitive and yet it is somewhat difficult for definition. 3. Forms of matter may change, but matter itself is neither destroyed nor created. 4. Newton's Law of universal gravitation is applied to matter in general. 5. About 90% of the matter of the Sun is hydrogen. 6. Matter is now regarded as being discontinuous. 7. Matter occupies space and it possesses mass. 8. Temperature is an intensive property; it doesn't matter how much substance is present. 9. As a matter of fact Robert Brown observed the movement of small solid particles in liquid quite unexpectedly. 10. Gas has no definite shape or volume. No matter what vessel it is placed in, the whole space of the vessel is occupied by gas. 11. The effect of continual movement of small solid particles suspended in a liquid is referred to as Brownian movement.1 2. His discovery is referred to in every text-book on physics. 13. This phenomenon is referred to as pressure exerted by gas. 14. The results of their experiments were referred to at the conference.

Atomic structure

Matter is composed of tiny particles called atoms. The atom is a complex unit of various particles, the most important of which are electrons, protons, and neutrons. The difference between atoms of different elements is due to differences in the number of protons and neutrons in the nucleus and to differences in the arrangement of the electrons surrounding the nucleus. The mass of the atom is concentrated almost entirely in the nucleus.

The chemical properties of different elements can be explained by the structure of the atom. Chemical changes involve a shifting of outer (valence) electrons so that a shell is achieved. The activity of metals and non-metals is related to the size of the atom and to the number of electrons in the external orbit. The valence or combining capacity of an atom is determined by the number of electrons it gains, loses or shares in chemical combinations with atoms of other elements. Atoms also may be joined to other atoms by sharing pairs of electrons. This process produces covalent compounds. These are generally gases or liquids with low boiling points. Oxidation involves the loss of electrons by the element. The process is accompanied by an algebraic increase in valence. Reduction, on the other hand, involves a gain of electrons by the substance reduced. This process is accompanied by an algebraic decrease in valence.