a) Participle I
1. A molecule is a compound consisting of two or more atoms.
2. Combininghydrogen with oxygen in the proportion of two atoms of hydrogen and one atom of oxygen we produce water.
3. Whenspeakingabout oxygen it is necessary to say that it is a colourless, odourless gas havingdensity at standard pressure and temperature of about one seven-hundredth that of water. It is soluble in water becoming liquid at about 180 °C.
4. While burningdifferent substances combine with oxygen.
5. The assistant was preparingthe solution very carefully.
6. The solution is boiling.
7. Theboilingsolution has neither colour nor odour.
b) Participle II
1. The solution of the problem required concentratedefforts of many scientists.
2. The data requiredwere analysedin our laboratory.
3. When required, thedata will be appliedin our practical work.
4. The investigations analysedresulted in an interesting discovery.
5. Heatedglass is plastic.
6. When heated,glass can be easily worked.
7. Some heat-resistant types of glasses can be heateduntil they are red and do not break, if then placedinto ice water.
8. Some new properties of the polymer foundduring the experiments were quite unexpected.