A1.1 Verb forms
1 Verb forms and patterns
When deciding on the correct verb form, there are three main things you need to consider:
✵ choice of tense (present; past)
✵ choice of aspect (perfect; continuous)
✵ choice of voice (active; passive)
Study Box: Common verb forms in academic scientific writing
1) The present is used to convey scientific facts, e.g.
DNA contains genetic information.
Much of the rain forest is being destroyed.
2) The present simple is also used to refer to current ideas in the literature, e.g.
Gayle concludes that extended use of the vaccine in schools would greatly benefit these communities.
There is general consensus on this in the literature.
3) The present perfect is often used to introduce general observations on the literature up to the present day, particularly in introductions, e.g.
There has been a great deal of research on alternative medicine.
To date, little research has focussed on the long-term effects of mobile phone use.
4) The past simple is used to refer to completed actions or states in the past, often combined with a specific time adverbial, e.g.
The first lunar landing occurred in 1969.
This use is sometimes linked to the narration of a series of events, along with the past continuous (to give background information), and the past perfect (to refer to a point in time before the current narrative).
The entire world was watching when the first humans landed on the moon. There had, of course, been earlier unmanned lunar missions, but the 1969 landing was a new milestone in space exploration.
5) The past simple passive is very commonly used to recount the methodology of scientific investigations, e.g.
The solution was heated to boiling point.
The subjects were monitored over a period of six months.
6) Note the tense use after if in conditional sentences.
If the structure weakens, the whole building will collapse.
(Present tense + WILL DO refers to future time. Denotes possible events/states.)
If people knew the risks, they would not take this drug.
(Past tense + WOULD DO refers to present time. Denotes unlikely events/states.)
If the government had implemented the safety standards earlier, more lives would have been saved.
(Past perfect + WOULD HAVE DONE refers to hypothetical event/state in the past.)
Other expressions are also used with the present tense to denote future: until; in case; provided that.
Find the errors in the verb forms and correct them.
1) Water is boiling at 100 degrees Celsius.
2) Ozone found naturally in the Earth’s stratosphere.
3) The World Wide Web has been invented in 1990.
4) Many different kinds of plastic were developed in recent years.
5) The effects of the drug have been showed in recent studies.
6) To date, little research is carried out on this area.
Write the verbs in the correct form.
1) The sun __________ (rise) in the east and __________ (set) in the west.
2) Pathogenic bacteria __________ (become) increasingly resistant to antibiotics.
3) In 1929, Edwin Hubble __________ (discover) that the universe (expand) __________ Hubble acknowledged that his discoveries were in many ways dependent on the work that __________ (do) by the many astronomers who came before him.
4) Since the early 1980s, developments in genetic engineering __________ (make) it possible to produce genetically modified crops.
5) In the initial study, a salt solution __________ (add) to the samples prior to centrifugation.
Write the verbs in the correct form.
1) The metal should be heated until it __________ (reach) a liquid state.
2) This type of building will not be safe if there __________ (be) an earthquake.
3) If governments __________ (implement) stricter controls on industry, carbon emissions __________ (fall), but this does not seem likely at the moment.
4) If the population __________ (vaccinate), the current measles outbreak __________ (prevent).
Practice (iv): Describing processes
Complete the text with the correct form of the verbs below, taking care to consider which of them need to be passive:
trap; heat; rely; carry; insulate; pump
Solar heating is a form of domestic or industrial heating that 1) __________ on the direct use of solar energy. The basic form of the solar heater is a thermal device in which a fluid 2) __________ by the sun’s rays in a collector and 3) __________ or allowed to flow round a circuit that provides some form of heat storage and some form of auxiliary heat source for use when the sun is not shining. The simplest form of a solar collector is the flat-plate collector, in which a blackened surface covered by one or more glass plates acts like a greenhouse and 4) __________ the maximum amount of solar energy. Tubes attached to the receiving surface 5) __________ air, water, or some other fluid to which the absorbed heat is transferred. The whole panel 6) __________ at the back and can thus form part of the roof of a building.
(Oxford Dictionary of Science, 2005: 761)