9. The science of chemistry

New words and word-combinations to be remembered:

chemical change хімічне перетворення

boiling point точка кипіння

solid state твердий стан

pure substance чиста речовина

building block будівельний блок

physical change фізичне перетворення

melting point точка плавлення

liquid state рідкий стан

to take place мати місце

gaseous state газоподібний стан

absorption поглинання, абсорбція

to accompany супроводити

behaviour поведінка

colour колір

combination поєднання

composition склад

compound сполука

density густина

detergent миючий засіб

determination визначення

drug лікарський препарат

dye барвник

explosive substance

вибухова речовина

hardness твердість, жорсткість

heat теплота

insecticide засіб для знищення комах

to" involve включати

to liberate вивільняти

mixture суміш

paint фарба

property властивості

smell запах

soap мило

solubility розчинність

substance речовина

to unite сполучатися

Chemistry is an experimental and theoretical study of the composition ion of matter and the changes that take place in matter. A chemical change involves changes in composition and in properties. A physical change involves only changes in properties with no change in composi­tion.

Chemical changes are usually accompanied by the liberation or the absorption of energy in the form of light, heat or electricity.

All forms of matter consist of either pure substances or mixtures of two or more pure substances. Elements are the building blocks of matter. Compounds are combinations of elements. Most of the elements are metals and most of them will unite with other elements and form compounds. The formation of a compound from simpler substances is known as synthesis. Analysis is the process of breaking down a compound into simpler substances or its elements and thus is the determination of its composition. The composition of a pure substance never changes.

Every substance has physical and chemical properties. Physical properties include colour, smell, solubility, density, hardness and boiling and melting points. Chemical properties include the behaviour with other materials.

Matter exists in three states: the solid, the liquid and the gaseous state. A substance can be transformed from one state to another under the changes of its temperature.

Chemistry is so much a part of our lives that it is very easily taken for granted. Metals, glass, plastics, dyes, drugs, insecticides, paints, paper, soaps, detergents, explosives and perfumes are all made of chemicals

Answer the following questions:

1. What is chemistry?

2. What does chemistry study?

3. What does a chemical change involve?

4. What does a physical change involve?

5. What does all forms of matter consist of?

6. What are elements?

7. What are compounds?

8. What is synthesis?

9. What is analysis?

10. What do physical properties include?

11. What do chemical properties include?

12. What states does matter exist in?

Speak on the science of chemistry using the following word-combi­nations:

— to be an experimental and theoretical study;

— to involve changes in composition and properties;

— elements, to be, the building blocks of matter;

— compounds, to be, combinations of elements;

—synthesis, to be, the formation of a compound;

—analysis, to be, the process of breaking down a compound;

—physical properties: color, smell, density, hardness, solubility;

—to exist in three states;

— substance, to be transformed, from one state to another.