Я відкриваю банку, коли хочу додати мед до чаю.

No. Банка means jar or can, not a financial bank.

In this sentence, банку most naturally means a jar, because honey is usually kept in a jar. So the image is probably opening a jar of honey.

A financial bank in Ukrainian is банк.

Because банку is the accusative singular form of банка.

Here, банку is the direct object of відкриваю (I open), so Ukrainian uses the accusative case:

• nominative: банка
• accusative: банку

This is very common for feminine nouns ending in -а:

• книга → книгу
• машина → машину
• банка → банку

Because Ukrainian present tense is often used for habitual or repeated actions, just like in English:

• I open the jar when I want to add honey to tea.

So я відкриваю банку does not have to mean only right now, at this moment. It can also mean this is what I usually do.

That is exactly what this sentence sounds like: a general habit or repeated situation.

Because відкриваю is imperfective, while відкрию is perfective future.

• відкривати / відкриваю = to open, be opening, open regularly
• відкрити / відкрию = to open once, complete the action

In this sentence, the speaker is describing a usual action, so the imperfective відкриваю is the natural choice.

Compare:

• Я відкриваю банку, коли хочу додати мед до чаю.
  = I open the jar when I want to add honey to tea. / That’s what I do.

• Я відкрию банку, коли захочу додати мед до чаю.
  = I will open the jar when I want to add honey to tea.

Because Ukrainian often omits subject pronouns when the verb ending already shows who the subject is.

• відкриваю already means I open
• хочу already means I want

So the second я is unnecessary. The sentence could technically say коли я хочу, but that would usually add emphasis or sound a bit heavier.

This is very normal in Ukrainian:

• Я читаю, коли хочу відпочити.
• Я йду, коли бачу, що вже пізно.

The subject stays understood.

Because it follows хочу (I want).

After want, Ukrainian usually uses an infinitive:

• хочу додати = want to add
• хочу читати = want to read
• хочу піти = want to go

So коли хочу додати мед до чаю literally has the structure when I want to add honey to tea.

This is an aspect question.

• додати = perfective, add once / complete the addition
• додавати = imperfective, be adding / add repeatedly / add in general

After хочу, either infinitive can be possible in some contexts, but they mean slightly different things.

Here, додати sounds natural because the speaker means to add some honey as a single completed act.

So:

• хочу додати мед до чаю = I want to add honey to tea
• хочу додавати мед до чаю = I want to be adding honey to tea / I want to add honey regularly

The perfective додати fits this sentence better.

Because мед is a masculine inanimate noun, and in the singular, masculine inanimate nouns usually have the same form in the nominative and accusative.

Here мед is the direct object of додати, so it is in the accusative, but the form stays the same:

• nominative: мед
• accusative: мед

This is normal for many masculine inanimate nouns:

• чай → чай
• хліб → хліб
• мед → мед

Because the verb додавати / додати commonly uses the pattern:

додати щось до чогось = to add something to something

So:

• додати мед до чаю
• додати цукор до кави
• додати сіль до супу

The preposition до requires the genitive case, which is why чай becomes чаю.

Because до takes the genitive case.

The base form is чай, but after до, it changes:

• nominative: чай
• genitive: чаю

So:

• до чаю = to the tea / to tea

This is one of the most common preposition + case patterns in Ukrainian:

• до дому
• до міста
• до чаю

Yes. Ukrainian word order is more flexible than English word order.

The original sentence is natural:

• Я відкриваю банку, коли хочу додати мед до чаю.

But you could also say:

• Коли хочу додати мед до чаю, я відкриваю банку.

Both are correct. The difference is mostly about emphasis:

• starting with Я відкриваю банку emphasizes the main action first
• starting with Коли хочу додати мед до чаю emphasizes the condition or situation first

Because коли хочу додати мед до чаю is a subordinate clause.

In Ukrainian, subordinate clauses are normally separated by commas, including clauses introduced by коли (when).

So the structure is:

• main clause: Я відкриваю банку
• subordinate clause: коли хочу додати мед до чаю

That is why the comma is required.

It most naturally describes a usual action or general habit.

The clue is the imperfective present відкриваю, together with коли хочу. It sounds like:

• whenever I want to add honey to tea, I open the jar

So the sentence is not mainly about one single event. It is about what the speaker generally does.

A useful stress pattern is:

• Я відкрива́ю ба́нку, коли́ хочу́ дода́ти мед до чаю́.

A few helpful points:

• відкрива́ю — stress on ва
• ба́нку — stress on ба
• коли́ — stress on the last syllable
• хочу́ — stress on the last syllable
• дода́ти — stress on да
• чаю́ — stress on the last syllable

Stress matters in Ukrainian, so it is good to learn words together with their stressed syllables.