VII. Define the part of speech the words in column a belong to. Match the words in column a with their definitions in column b.

A	B
1. dissolve	a) higher than or above something
2. expel	b) to have an effect on each other or something else
3. excess	c) to force something out from a container
4. pour	d) a larger amount than is needed or usual
5. interact	e) to cause a liquid or a loose substance to flow into or out of a container
6. upper	f) suitable or correct
7. proper	g) to make or to become liquid when put into a liquid

VIII. Fill in the blanks with the words given in the box. Pay attention to the verb forms necessary in each case – their Tense and Voice – when put the verbs from the box.

Nouns	Adjectives	Verbs
colour form outlet solids	commercial complete hydrochloric spherical	to dissolve to involve to react to redden

1. If we … some hydrogen chloride in water the solution has sour taste, … blue litmus, … with zinc.

2. When all the sodium chloride in the flask has been transformed, the reaction is … .

3. The upper … funnel of the Kipp’s apparatus contains the solution of … acid.

4. Hydrogen formed comes out through the … of the Kipp gas generator.

5. Salts are … at room temperature.

6. Crystals of salts vary in … and … .

7. There are some laboratory and … methods by which salts may be prepared.

8. Most methods to prepare salts … double replacement reaction.

IX. Answer the questions to the text and discuss some aspects of experiments in chemistry.

1. Why do chemists conduct experiments in a laboratory?

2. How is hydrogen chloride prepared in a laboratory? Represent this reaction by the equation.

3. How can we define that hydrogen chloride is produced? What are the main characteristics of the hydrogen chloride (smell, colour, solubility, weight)?

4. Is it possible to turn hydrogen chloride into a solution of hydrochloric acid? How? What is necessary to do? Represent it in the form of equation.

5. What is the chemical mechanism of obtaining hydrogen in a laboratory? Express this explanation in the equation.

6. What is Kipp gas generator used for? Give the general description of the Kipp gas generator.

7. What does the word “salt” denote?

8. What are the main characteristics of salts (smell, colour, solubility, weight)?

9. What methods of preparing salts exist in chemistry?

10. Describe in detail an example of preparing salt.

X. Look through this text and find the answer to the question “What substances influence the course of a chemical reaction?”

Hundreds years ago a chemist carefully put a platinum wire into a container with a mixture of hydrogen and oxygen. The result was extraordinary. The container filled up with fog in the form of water vapour. The temperature and pressure remained unchanged, but the reaction between hydrogen and oxygen occurred in few seconds. The platinum wire which made the two gases to combine instantly underwent absolutely no change. Its appearance, chemical composition and weight were exactly the same after the experiment.

This experiment was done by a serious investigator, the German chemist Dobereiner. The phenomenon he observed is now called catalysis. Substances capable of making reactions to occur faster are called catalysts. Catalysts are very numerous. They may be metals – solid or powdered, oxides of great variety of elements, salts or bases. They may be used in pure form or as mixtures.

Not every substance can accelerate any chemical process. So, chemists say that catalysts are selective in their action: they may influence one reaction strongly without affecting another. Of course, there are exceptions to this rule. For example, aluminium oxide is capable of catalyzing several dozen different synthesis reactions of organic and inorganic compounds. Finally, different catalysts can make a mixture of the same substances react in a different way to form different products.

There are also substances with surprising properties, called promoters. They do not influence the course of the reaction, neither accelerating nor slowing it. But if added to a catalyst, they accelerate the reaction greater than the catalyst itself. A platinum wire with “impurities” of iron, aluminium, or silicon dioxide, would cause an absolutely impressive effect to a mixture of hydrogen and oxygen.

There are also anticatalysis and anticatalysts. Scientists called them inhibitors. Their purpose is to slow down rapid chemical reactions.

* Read carefully the text above. Study carefully the information about the substances, which influence the course of chemical reaction, and be ready to discuss their properties (see the questions below).

* Questions for discussion

1. What are the substances which influence the course of chemical reactions?

2. What chemical properties do catalysts have?

3. What catalysts do you know?

4. What catalysts do you usually use in the University laboratories when conducting experiments?

5. What substances have the effect opposite to catalysts in the course of chemical reactions?

6. Do you have any experience in applying inhibitors?

7. Is it possible or necessary to use catalysts (or inhibitors) in the experiments described in the main topical texts (exercise IV)?