The past tense of "they are doing an experiment" is "they were doing an experiment".
The past tense of scent is scented. For example, "She scented the flowers in the vase."
The word "sublimation" is a noun and so doesn't have a past tense. Only verbs have tenses.
Condensate is primarily used as a noun. If it's being used as a verb the past tense is condensated.
To separate three substances in the past tense, you would write: "I separated three substances."
the past tense of am is was and the past tense of has is had
The past tense of "has" is "had" and the past tense of "have" is "had."
Was and were are both the past tense of be. The present tense is: I am he is you are they are The past tense is: I was he was you were they were
"will be" is the future tense of "be". The past tense of "be" is "was/were".
The past tense of "she do" is "she did."
The word "were" is past tense. It is the past tense of the verb "to be."
The past tense of "will" is "would" and the past tense of "be" is "was" or "were" depending on the subject (singular or plural).
HAD is the Past Tense of TO HAVE.
The past tense of "am" is "was" and the past perfect tense of "has" is "had."
The past tense of "have" is "had."
The past tense of "you will not" is "you would not."
The past tense of "exist" is "existed." The past perfect tense is "had existed."