The document discusses the use of modal verbs in the past tense. It explains that modal verbs like "can" change to "could" in the past, while other modals use a structure of "modal + have + past participle verb". Examples are given like "You should have gone" and "He must have gone home". The document also covers using modals in the past with passive voice, with the structure "modal + have + been + past participle". Practice exercises are included for students to write sentences using modals in the past.

1. Modals:
Past with Passive
RobertWilks
English Level 8
ITESO

2. Structures of modals in past
Can in present becomes could in past.
(meaning ability)

3. Structures of modals in past
Other modals have a different
structure and special meanings when
used in the past.
modal + have +Verb past participle

4. Examples
▪ You should have gone to the movie. It was great!
(The person he’s speaking to didn’t go – advice in the past)
▪ George is not at work right now. He must have gone home.
(Speculation about the past – nearly 100% certain)
▪ Janet didn’t attend class today. She might have been sick.
(Speculation about the past – 50% certainty – “could” can
be substituted for “might” in this situation)
▪ The public can’t have seen the results yet because the
work was done in secret.
(something was impossible in the past)

5. Practice with modals in the past
Write the verb structures in past, using the
modal and the verb shown.
Example:
▪ The company ___________ (should, train) the
workers more effectively.
▪ The company should have trained the
workers more effectively.

6. Practice with modals in the past
1. Julie __________ (can) read when she was only 4 years old.
2.The scientists __________ (should, verify) the results
before publishing the paper.
3.The chemotherapy __________ (must, be) effective,
because the tumor is now gone.
4.These findings are not consistent with the other
experiments.They ___________ (might, change) the
procedures.
5.The students __________ (can’t, make) high scores on the
quiz because they were using social media at the same time.

7. Check your answers
1. Julie could read when she was only 4 years old.
2.The scientists should have verified the results before
publishing the paper.
3.The chemotherapy must have been effective, because the
tumor is now gone.
4.These findings are not consistent with the other
experiments.They might have changed the procedures.
5.The students can’t have made high scores on the quiz
because they were using social media at the same time.

8. Past Modals with PassiveVoice
Remember:
Passive voice focuses on the object
that receives the action instead of the
subject that does the action.
Past modals with PassiveVoice use
“been”.

9. Structure
modal + have + been +Verb past participle

10. Examples of Past Modals with PassiveVoice
▪ There is a report on my desk.The project must have been
completed.
(Speculation, nearly 100% certain; project receives the action).
▪ There are no more salmon in the river.They might have been
killed by the pollution.
(Speculation, 50% certain; salmon receives the action)
▪ This order still hasn’t been filled? It should have been filled last
week.
(It wasn’t filled, but there was a requirement to fill it – order
receives the action)

11. Practice Past Modals with PassiveVoice
Write the verb structures in past, using the modal
and the verb shown.
Example:
▪ The number of cases of malaria __________ (could,
reduce) if they had used the new vaccine.
▪ The number of cases of malaria could have been
reduced if they had used the new vaccine.

12. Practice Past Modals with PassiveVoice
1. Ellen took that medicine and then she became sleepy.The sleepiness
______________ (must, cause) by the medicine.
2. People are taking better care of their teeth than they were 100 years
ago, and there is much less incidence of tooth decay. Better oral health
_______________ (might, produce) by these habits.
3. Everyone who ate at that restaurant last night got sick. Proper food
handling practices ____________ (should, implement).
4.The cases of Zika _____________ (might, spread) by mosquitoes.
5.The incidence of polio fell dramatically after the vaccine was widely
administered.The disease __________ (must, prevent) by the vaccine.

13. Check your answers
1. Ellen took that medicine and then she became sleepy.The sleepiness
must have been caused by the medicine.
2. People are taking better care of their teeth than they were 100 years
ago, and there is much less incidence of tooth decay. Better oral health
might have been produced by these habits.
3. Everyone who ate at that restaurant last night got sick. Proper food
handling practices should have been implemented.
4.The cases of Zika might have been spread by mosquitoes.
5.The incidence of polio fell dramatically after the vaccine was widely
administered.The disease must have been prevented by the vaccine.

14. Pronunciation
When you say the structures above, “have”
is always reduced to a very short, soft
sound – like a contraction “–‘ve.”

15. Pronunciation
Practice saying these examples:
▪You should’ve gone to the movie.
▪He must’ve gone home.
▪She might’ve been sick.
▪The project must’ve been completed.
▪The order should’ve been filled.