Könnten Sie bitte Backpapier auf das Blech legen und den Ofen vorheizen?

Könnten Sie ...? is a more polite, less direct way to make a request. It is the Konjunktiv II form of können and works a lot like English Could you ...?

• Können Sie ...? = Can you ...? / Are you able to ...?
• Könnten Sie ...? = Could you ...? / a softer, more polite request

In everyday German, this is a very common way to sound courteous.

Capital Sie is the formal word for you in German.

This is different from:

• sie = she
• sie = they

So in this sentence, Sie tells you the speaker is addressing someone formally, such as a customer, colleague, stranger, or guest.

You would usually use du instead of formal Sie.

A natural informal version would be:

Könntest du bitte Backpapier auf das Blech legen und den Ofen vorheizen?

That is the informal equivalent of Could you please ...?

If you were speaking to several people informally, you might use:

Könntet ihr bitte ...?

Because könnten is a modal verb, and in German modal verbs push the main verb to the end in the infinitive form.

So the structure is:

• Könnten = the finite modal verb
• Sie = subject
• the rest of the sentence
• legen and vorheizen = infinitives at the end

This is very normal German word order:

• Sie können den Ofen vorheizen.
• Könnten Sie den Ofen vorheizen?

When there are two main verbs connected by und, both usually stay at the end:

• ... legen und ... vorheizen

Because auf can take either the accusative or the dative, depending on meaning.

• auf das Blech = movement onto the tray
• auf dem Blech = location on the tray

Here, the action is putting the baking paper onto the tray, so German uses accusative:

• Backpapier auf das Blech legen

If you were describing where it already is, you would use dative:

• Das Backpapier liegt auf dem Blech.

This is a very common German pattern:

• motion/change of position → accusative
• location/no movement → dative

Yes. Auf das is often contracted to aufs.

So this would also be correct and very natural:

Könnten Sie bitte Backpapier aufs Blech legen und den Ofen vorheizen?

Both are correct:

• auf das Blech = a little more explicit
• aufs Blech = very common in everyday German

Because den Ofen is the accusative form of der Ofen.

The verb vorheizen takes a direct object, and that object must be in the accusative:

• der Ofen = nominative
• den Ofen = accusative

So:

• Der Ofen ist heiß. = the oven is hot
• Ich heize den Ofen vor. = I preheat the oven

Since the sentence is asking someone to preheat the oven, Ofen appears in the accusative: den Ofen.

Yes. Vorheizen is a separable-prefix verb.

That means:

• In an infinitive or after a modal verb, it stays together:
  den Ofen vorheizen
• In a normal finite clause, the prefix often separates:
  Sie heizen den Ofen vor.

Examples:

• Ich will den Ofen vorheizen.
• Ich heize den Ofen vor.

So in your sentence, it stays together because it is at the end as an infinitive after könnten.

In German, words for materials or uncountable substances often appear without an article when speaking generally.

So Backpapier here is being treated like a material or substance, not as one specific item.

That is why Backpapier auf das Blech legen sounds natural.

You could also hear:

• das Backpapier if a specific baking paper is meant
• ein Stück Backpapier if you want to emphasize a piece/sheet of baking paper

So the version in the sentence is normal and idiomatic.

In everyday kitchen German, das Blech usually means a baking tray or baking sheet.

Literally, Blech can also mean sheet metal or metal plate, but in cooking context it very often refers to the oven tray.

A more explicit word is:

• das Backblech = baking tray / baking sheet

In many situations, native speakers simply shorten that to:

• das Blech

So here, das Blech is understood as the tray that goes into the oven.

Bitte makes the request polite, just like please in English.

Its exact position is somewhat flexible. In your sentence, Könnten Sie bitte ...? is very natural.

You may also hear things like:

• Könnten Sie Backpapier auf das Blech legen und bitte den Ofen vorheizen?
• Könnten Sie Backpapier auf das Blech legen und den Ofen bitte vorheizen?

But Könnten Sie bitte ...? is one of the most common and smooth-sounding placements.

Because the two actions are connected by und and share the same subject and modal verb.

So German does not need to repeat Könnten Sie:

• Könnten Sie bitte Backpapier auf das Blech legen und den Ofen vorheizen?

This is understood as:

• Could you please do action 1
• and do action 2

You could repeat it, but it would usually sound heavier or more formal than necessary.

Normally, no.

In this sentence, und simply connects two infinitive phrases under the same modal verb, so no comma is needed:

Könnten Sie bitte Backpapier auf das Blech legen und den Ofen vorheizen?

That is the standard punctuation.

Yes, definitely.

Both are possible:

• das Blech = shorter, very common in kitchen context
• das Backblech = more specific and explicit

So you could also say:

Könnten Sie bitte Backpapier auf das Backblech legen und den Ofen vorheizen?

That may be especially helpful for learners, because it makes the meaning clearer.