5. Look at the picture and comment on it from the point of view of chemistry.

6. Read the following words and word-combinations.

negatively charged	micelle
immiscible liquid	slightly oily coating
soap-water solution	evaporate
trap the fats	emulsifier

Replace the words in Russian with the words and word-combinations above. Translate the text.

How does soap work?

Soap is a cleansing agent, and is made from the interaction of fats and oils with alkalis. Each soap molecule has a long hydrocarbon chain, sometimes called its 'tail', with a carboxylate 'head'. In water, the sodium or potassium ions float free, leaving a отрицательно заряженную head.

S oap is an excellent cleanser because of its ability to act as an emulsifying agent. An эмульгатор is capable of dispersing one liquid into another несмешивающуюся жидкость. Nearly all chemical compounds fall into two categories: hydrophilic and hydrophobic. Water and any substance that will mix with it are hydrophilic. Oil and any substance that will mix with it are hydrophobic. When water and oil are mixed they get separated, which is why hydrophilic and hydrophobic compounds cannot form a mixture. When grease or oil is mixed with a мыльно-водным раствором, the soap molecules work as a bridge between polar water molecules and non-polar oil molecules.

Since soap molecules have both the properties of non-polar and polar molecules, soap will form micelles and захватит жиры within them. Since the мицелла is soluble in water, it can easily be washed away. A good hosing down with plain water with a little rubbing will do a reasonable job of removing the dirt. Soap is not really necessary for the job. However, if the dirt particles have a слегка жирное покрытие, then they will stick to your skin like wet mud. Your skin also has enough oil on it to make the dirt particles stick. But unlike the mud, this dirt is going to stay stuck because oil doesn't испаряется, and dry up as water does. To remove the oil adhering dirt, is to seek out and destroy the sticky oil itself. A liquid can then be applied, and the dirt will fall off and be swept away.

7. Speak upon the following topics:

1 . Physical chemistry as a science.

2. Thermodynamics as a branch of physical chemistry.

3. Electrochemistry. Electrolysis.

4. Chemical kinetics.

5. Colloidal chemistry.

6. Modern physical chemistry.

8. Work on your own or with a partner. Make up a list of key facts from the text B. Be ready to summarize the text orally using your list.

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