Texts on specialities
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
detergent миючий засіб
drug лікарський препарaт
explosive substance вибухова речовина
hardness твердість, жорсткість
insecticide засіб для знищення комах
to involve включати
to liberate вивільняти
to unite сполучатися
Chemistry is an experimental and theoretical study of the composition 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 color, smell, solubility, density, hardness and boiling and melting points. Chemical properties include the behavior 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 lor granted. Metals, glass, plastics, dyes, drugs, insecticides, paints, paper, soaps, detergents, explosives and perfumes are all made of chemicals.
I. 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?
II. 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.