Breakdown of Пока я смешиваю эти жидкости, идёт химическая реакция.
я
I
этот
this [f: эта, n: это]
идти
to go (on foot) / to proceed, go (of a process)
пока
while
Questions & Answers about Пока я смешиваю эти жидкости, идёт химическая реакция.
How do I know пока means "while" here and not "until" or "for now"?
When пока connects two clauses and doesn't have the negative particle не, it means "while" or "as long as". If you wanted to say "until", you would use пока не, which is usually followed by a perfective verb to show a result.
Why do both clauses use imperfective verbs (смешиваю and идёт)?
Because both actions are continuous and happening at the exact same time. When using пока to mean "while" for two simultaneous ongoing actions, you need imperfective verbs in both parts of the sentence.
Why is the verb идёт used for a chemical reaction? Doesn't it mean "to walk"?
The verb идти literally means "to go" on foot, but it is used in many everyday expressions to mean a process "is happening" or "is in progress". Just like we say a meeting or a movie "is going on" in English, Russians say идёт химическая реакция.
Why does эти жидкости look like it is in the nominative case if it is the object of the sentence?
It is actually in the accusative case, as it is the direct object of смешиваю (mixing). For all inanimate plural nouns in Russian, the accusative case form is identical to the nominative case form.