IV. Speaking

Give a short summary of the text, signifying all the stages of the development of chemistry.

V. Reading

a. Guess if the following statements are true or false. If they are false correct them.

1. Chemistry can be divided into two branches. T/F

2. Organic chemistry is the chemistry of the compounds of carbon. T/F

3. Inorganic and organic chemistry don`t have any differences. T/F

4. Chemical reaction is a process. T/F

5. General chemistry is the introduction to the entire science. T/F

6. An acid is a liquid. T/F

7. Biochemistry is the chemistry of industrial processes. T/F

Text B

Chemistry and its branches

The science that we can define as the study of formation, composition, structure and reactions of the chemical elements and their compounds is called chemistry. An element is a chemical unit that can`t be broken down. Each element is represented by a chemical symbol and has a set of properties that distinguishes it from other elements. All elements are made of atoms. An atom is the smallest particle of an element that retains the characteristics of that element.

All elements combine to form different substances with new properties. Such substances made from elements combined chemically are called compounds. Acids and bases are common groups of compounds. An acid is a substance that releases hydrogen ions when mixed with water. A base is a substance which separates in water forming ions that react with hydrogen ions.

The process by which elements react to form new compounds can be described as chemical reaction. There are two types of chemical reactions. In some reactions the breaking of bonds absorbs more energy, in others the breaking of bonds absorbs less energy.

Most chemical reactions occur more easily when the reacting substances are in water solution. Water is a key component of cells and provides the medium through which nutrients enter and wastes exit a living cell. A solution is a class of mixtures in which individual molecules of substances are distributed. The formation of a solution is a physical change. Solution has two parts: solvent and solute. The solvent is the medium in which some substances are dissolved. The solute is the substance dissolved in the solvent. There are two kinds of substances: soluble that dissolve in a solvent and insoluble that don`t dissolve in a particular solvent.

Chemistry can be divided into the following branches: general, analytical, organic and inorganic, physical, industrial, structural and biochemistry. General chemistry is the introduction to the entire science. Analytical chemistry deals with the methods of separation of pure substances from mixtures. Physical chemistry is the study of relations between the properties of substances and their ability to react with other substances. Industrial chemistry is the chemistry of industrial processes. Structural chemistry deals with the molecular structure and its relation to the properties of substances. Organic and inorganic chemistry progress side by side, but have some differences. Organic chemistry is the chemistry of the compounds of carbon. Inorganic chemistry is the chemistry dealing with the preparation of new compounds and the methods of their analysis.

Biochemistry is the chemistry of living organisms and of vital processes. Sometimes it is called physiological chemistry. It studies molecules of the living systems. Every life process depends on protein molecules: they direct and regulate metabolism in the body, destroy infections, etc. There are more than 100 aminoacids known to biochemists. They are of great importance to our organism. Biochemistry is a rapidly expanding area of biomedical science.

b. Fill in each gap with the words listed:

solution, chemical reaction, compounds, mass, key component, solvent, represented, dissolved.

1. Matter is something that has a .................... .

2. Each element is...........................by a chemical symbol.

3. .......................is the process by which elements react to form new compounds.

4. Water is a ........................ of cells and provides the medium.

5. A………………...is a class of mixtures.

6. Solute is a substance .............................in the solvent.

7. Acids and bases are two groups of ……………...that react in water.

8. Substances that do not dissolve in a particular.............. are called insoluble.

c. Make up word combinations.

1.element water 2.solution 3.substance 4.process	1.unit chemical 2.storage 3.reaction 4.symbol
1.solution living 2.acid 3.sentence 4.cell	key 1. base 2. component 3. process 4. acid

d. Write questions to the words in italics.

1. Matter is something that has a mass and takes up space.

2. Each element is represented by a chemical symbol.

3. The element has a set of properties that distinguishes it from other elements.

4. The formation of a solution is a physical change.

5. There are two kinds of substances: soluble and insoluble.

6. Biochemistry studies molecules of the living systems.

7. There are more than 100 aminoacids known.

e. Find out the derivatives of the following words. Then complete the sentences with an appropriate derivative.

… … …

↑ ↑ ↑

… ← solution → … … ← science → … … ← purity → …

↓ ↓

… …

1. Water is an excellent ……….

2. All plants and factories must have the system of ……..… of industrial wastes.

3. … water can be prepared by distillation, filtration or boiling.

4. Most of the substances are … in water.

5. Biology is the … study of the life and structure of plants and animals.

6. …can be defined as a homogenous mixture of one or more substances.

7. Natural waters have different ….

8. Mathematics is the … of numbers and shapes.

9. … is one of the chemical properties of a substance.

10. Providing … of water pools in our country is one of the most important ecological problems.

11. If we … some of the hydrochloric acid gas in water, the solution has a sour taste.