Um zu vs Zum – Interchangeable?

Question

Ich gehe in den Park, um zu essen.

Or:

Ich gehe in den Park zum Essen.

Both say that I plan to eat in the park, so do they both work?

Ich gehe nach Hause zum Schlafen.

Or:

Ich gehe nach Hause um zu schlafen.

If not both of them work, which one is correct in both examples?

It feels to me that um zu is stronger than zum – I can't sleep anywhere but my house, or I only eat at parks.

Answer 1

In your examples - when you have specific goal, for example:

Ich gehe in den Park, um Hamburger zu essen. Here I would use um zu because I specifically go because of the Hamburger.

If it is general - Ich gehe in den Park zum Essen. Here I don't have a specific goal but eating in general, so I would use zum.

As you mentioned in your question, um zu is stronger than zu - you need a specific goal to use it.

Answer 2

Infinitive Groups

Um zu initiates an infinitive group which is usually an adverbial determination. It describes the objective of a prerequisite or the purpose of a circumstance (final clause). Examples:

Ich gehe in den Park, um zu essen.

The circumstance is that you will go into the park and the purpose of this action is that you want to eat there.

Ich gehe nach Hause, um zu schlafen.

The circumstance is that you will go home and the purpose of this action is to sleep.

Ich bin zu müde, um nachher noch in den Park zu gehen.

The prerequisite is that you are tired and the objective of this is that you cannot go into the park.

There are also other conjunctions:

• um – final clause (objective or purpose)
• ohne – negation, restriction (actions or facts which do not occur together with the events mentioned in the main sentence)
• (an)statt – alternative circumstances, substitution sentence (something other than the expected situation happens)
• außer – restrictive sentence (restricts the scope of the events mentioned in the main sentence)
• als – comparative sentence (compares the statement of the subordinate clause with the statement of the main clause)

Nominalization (similar to English gerund)

Nominalization is the use of a word which is not a noun (usually a verb) as a noun. If there is an article in front of the verb, it is nominalized and therefore we capitalize it. Articles sometimes hide, e. g. zum is short for zu dem. So it contains an article.

Nominalization can be used equivalent to infinitive groups, however it is usually used for shorter phrases, since it is difficult to form larger nominalized phrases and if you do it sounds strange. Examples:

Zum Schlafen gehe ich nach Hause. = Um zu schlafen, gehe ich nach Hause.

Zum Essen gehe ich in den Park. = Um zu essen, gehe ich in den Park.

This is an example where a nominalization does not make sense:

Statt des Putzens des Hauses sehe ich mir lieber einen Film an. = Anstatt das Haus zu putzen, sehe ich mir lieber einen Film an.

The following equivalences exist:

• um zu – zum

Um zu essen, gehe ich nach Hause.

Zum Essen gehe ich nach Hause.

• ohne

Ohne die Katze gefüttert zu haben, gehe ich zur Arbeit.

Ohne das Füttern der Katze gehe ich zur Arbeit.

• anstatt

Anstatt zu spielen, solltest du lieber deine Hausaufgaben erledigen.

Statt des Spielens solltest du lieber deine Hausaufgaben erledigen.

• außer

Ich konnte nichts tun, außer die Polizei zu rufen.

Ich konnte außer des Rufens der Polizei nichts tun.

• als

Es ist besser nach Hause zu gehen, als sich zu verletzen.

Das Nachhausegehen ist besser als das Verletzen.

However, as you see, both are not always perfectly interchangeable, hence one should not use nominalization for longer phrases.