2. Adverbial clauses of condition containing had, were, could, should are introduced without any conjunction to make the sentences more emphatic. In these cases we find inversion:

If I had time, I would come over.

Had I time, I would come over.

If I were at your place, I would call him.

Were I at your place, I would call him.

Ex. 2. a) Tell what you will do if you are free on Sunday. (Type I). Use the suggestions given below.

to go on a trip to Vilnius, to go to the cinema (theatre), to read up for the examination, to go on an excursion, to study the lessons carefully, ( your idea).

b) Tell what you would do if you did not understand some phenomenon. (Type II).

to ask one of the friends to explain it, to try to understand by oneself, to ask the teacher to explain it, to read the necessary literature about it.

c) Tell what you would have done if you had had much time last month. (Type III).

to go hiking, to complete the experiment, to finish the research work, to go on an excursion to Moscow, (your suggestion).

Ex. 3. Change the following sentences of real condition a) to unreal condition I, b) to unreal condition II.

1. If anybody asks for you, I will tell him to call back later. 2. If you study these lessons carefully, you will be able to answer all the questions. 3. If he asks me, I will gladly help him. 4. The teacher will get angry with me if I make that mistake again. 5. If the experiment is interesting, I will carry it out.

Ex. 4. Use the correct tense form of the verb in brackets in each sentence.

1. He would have spoken to Mr. Carrington if he (to see) him yesterday. 2. If she (not to know) the answer, she always admits it right away. 3. I (to believe) it if I had seen it with my own eyes. 4. But for your advice, I (not to be able to) solve my problems. 5. If you (to go on) making so much noise, I will send you out. 6. Provided zinc were heated with sulphuric acid, the metal (to replace) hydrogen. 7. The study of any substance (to be) incomplete unless we investigated the properties of that substance and the methods of obtaining its components.

Ex. 5. Substitute the word ``unless`` for ``if…not``. Study the Model.

Model: If you do not leave immediately, you will be late for the lecture. Unless you leave immediately , you will be late for the lecture.

1. She wouldn’t do that if she were not allowed to. 2. If you don’t study harder, you are going to fail at the examination. 3. If you don’t understand my instructions, read them again. 4. If iron is not heated red-hot, it won’t absorb any carbon. 5. If he hadn’t followed the instructions, he wouldn’t have obtained good results.

Ex. 6. State the type of each conditional sentence. Translate these sentences into Russian.

1. If the gas were pure, we could immediately use the Gas Law to calculate the number of moles produced by the reaction. 2. If Gibbs had never published another paper, this single contribution ``On the Equilibrium of Heterogeneous Substances`` would have placed him among the greatest theoreticians in the history of science. 3. The collisions of the molecules result in no loss of energy. If energy were lost, the temperature and pressure would fall. 4. If the temperature of the liquid is constant, the molecules will escape from the surface at a constant rate. 5. Unless this method of study had been adopted, the students would have become engulfed in a mass of complicated phenomena from which it is quite doubtful whether they could have extricated themselves. 6. If water in an open vessel were heated, the vessel would soon become dry. 7. If liquid water is sufficiently cooled, it freezes, i. e. it changes to the solid state. 8. If this were so, fluorine gas in contact with chloride ion would remove the electron from the chloride ion and, thereby, form fluoride ion. 9. This is about half the amount of energy that would be evolved if a mole of sodium metal reacted with chlorine to form NaCL.

Ex. 7. Restate the sentences using the indirect order and translate them. Study the Model.

Model: If it were not so late, they would complete their experiment. Were it not so late, they would complete their experiment.

1. If the enthalpy change were positive, the reaction could not occur by itself. 2. If this reaction could be shown to be spontaneous, it might offer an ideal way to remove two of the most serious air pollutants, carbon monoxide and nitric oxide. 3. If we had understood the reaction mechanism, we should have been able to raise the rate of the reaction or, if necessary, to slow it down. 4. If they had investigated the properties of this substance, they would have been careful. 5. If the sodium chloride were prepared by passing hydrogen chloride gas into a dilute solution of sodium hydroxide, much heat would evolve. 6. The substance might have been identified if we had known the properties it possessed.