Learn Hardcore German: Mein alter Laptop ist gestern kaputtgegangen.

verbs of movement from A to B: gehen, kommen, fahren, fliegen
verbs of change of state: einschlafen, sterben, wachsen, verschwinden, etc.

Kaputtgehen describes a change of state (from working → broken), so it takes sein:

Mein alter Laptop ist gestern kaputtgegangen.
= My old laptop broke yesterday.

If kaputtmachen were used (to break something actively), it would take haben:

Ich habe den Laptop kaputtgemacht.
= I broke the laptop.

Why is kaputtgegangen written as one word, and where does the ge- go?

The basic verb is kaputtgehen (to break, to stop working). It is a separable verb:

infinitive: kaputtgehen
present: Der Laptop geht kaputt.
simple past: Der Laptop ging kaputt.

In the Perfekt, separable verbs split into:

prefix (here: kaputt)
ge-
- past stem
  - -en / -t

So:

gehen → gegangen
add the separable part in front: kaputt + gegangen = kaputtgegangen

Word order in the sentence:

ist (conjugated auxiliary in 2nd position)
kaputtgegangen (past participle at the end)

So you get:

Mein alter Laptop ist gestern kaputtgegangen.

Spelling: kaputtgehen and kaputtgegangen are written as one word in modern standard German.

Can I also say Mein alter Laptop ging gestern kaputt? Is there a difference?

Yes, that sentence is correct:

Mein alter Laptop ging gestern kaputt.

Difference:

ist kaputtgegangen = Perfekt (present perfect)
ging kaputt = Präteritum (simple past)

In spoken German, people usually prefer the Perfekt:

Mein alter Laptop ist gestern kaputtgegangen. (more natural in everyday speech)

In written German (narratives, reports, fiction), the Präteritum is more common:

Mein alter Laptop ging gestern kaputt.

In meaning, they are basically the same here; it’s more about style and register than time/aspect (unlike English has broken vs broke).

Why is it Mein alter Laptop and not Mein alte Laptop or Mein alten Laptop?

This is about adjective endings.

Laptop is masculine: der Laptop
In this sentence, Laptop is the subject → nominative case
singular, nominative, masculine, with a possessive determiner (mein)

In this pattern, the adjective takes the ending -er:

mein (no ending)
alter (with -er)
Laptop

So:

Mein alter Laptop … ✅
Not:
Mein alte Laptop … ❌
Mein alten Laptop … ❌

A quick mini-paradigm for Laptop:

Nominative: Mein alter Laptop ist kaputt.
Accusative: Ich habe meinen alten Laptop verkauft.
Dative: Mit meinem alten Laptop hatte ich Probleme.

How can I know that Laptop is masculine (der)?

Unfortunately, for most modern loanwords like Laptop, there is no reliable rule; you usually have to learn the gender together with the noun.

Some hints:

Many technical devices that are similar to Computer tend to be masculine:
der Computer, der Monitor, der Drucker, der Fernseher
and der Laptop fits into that group.
Dictionaries always list nouns with their gender:
- der Laptop

So when you learn a new noun, learn it as a full chunk:

der Laptop, not just Laptop
So you can produce forms like mein alter Laptop, den alten Laptop, etc.

Why is gestern in the middle and not at the end like in English (broke yesterday)?

Typical neutral word order for adverbs in German main clauses follows the TMP rule:

Time
Manner
Place

In your sentence, gestern expresses time, and a time adverb usually comes before the main verb complex at the end:

Mein alter Laptop ist gestern kaputtgegangen.

You can also move the time element to the beginning for emphasis or to link with previous context:

Gestern ist mein alter Laptop kaputtgegangen.

Putting gestern at the very end:

Mein alter Laptop ist kaputtgegangen gestern.

is possible in some colloquial speech, but sounds less standard and more marked. The most natural neutral version is the original: … ist gestern kaputtgegangen.

Where does the verb go in a normal German main clause like this?

German main clauses are generally verb-second (V2):

First position: one element (subject, time, object, etc.)
Second position: conjugated verb (here: ist)
Then the rest of the sentence
If there’s a participle or infinitive, it goes to the end

In your sentence:

Mein alter Laptop → subject (1st position)
ist → conjugated verb (2nd position)
gestern → time adverb
kaputtgegangen → past participle at the end

So the skeleton is:

[X] – ist – … – kaputtgegangen.

If you start with Gestern, you still keep the verb in 2nd position:

Gestern (1)
ist (2)
mein alter Laptop (…)
kaputtgegangen (end)

Is kaputt an adjective or an adverb here? What does kaputtgehen literally mean?

Originally, kaputt is an adjective meaning broken:

Der Laptop ist kaputt.
= The laptop is broken.

In kaputtgehen, it forms a compound separable verb with gehen:

kaputtgehen = literally to go broken → to break / to stop working

So:

Der Laptop geht kaputt.
= The laptop is getting broken / breaking.

Over time, kaputtgehen is treated as a single verb with its own meaning: a device stops working, breaks down. The gehen part does not mean to walk here anymore; it just indicates a change of state.

Could I say Mein alter Laptop ist gestern kaputt geworden instead?

You can say:

Mein alter Laptop ist gestern kaputt geworden.

It is grammatically correct, but in this context it sounds less idiomatic than ist kaputtgegangen.

Nuances:

ist kaputtgegangen → the standard, very common way to say a device broke (especially mechanical/electronic things).
ist kaputt geworden → more like became broken, somewhat less common, a bit more descriptive.

In everyday speech about devices, native speakers strongly prefer:

Mein alter Laptop ist gestern kaputtgegangen. ✅

Why do you use a perfect tense (ist kaputtgegangen) instead of a simple past like English broke?

English distinguishes clearly between:

simple past: My laptop broke.
present perfect: My laptop has broken.

In German, the distinction between Perfekt and Präteritum is less about aspect and more about style / register:

Perfekt (ist kaputtgegangen) is the usual past form in spoken German.
Präteritum (ging kaputt) is common in written narratives, newspapers, books, etc.

Both normally refer to a finished past event. So ist kaputtgegangen here is simply the normal conversational way to say broke.

Why is it just gestern and not am gestern or an dem gestern?

Some time expressions in German are used without any article or preposition, as bare adverbs:

gestern = yesterday
heute = today
morgen = tomorrow

So you say:

Mein alter Laptop ist gestern kaputtgegangen. ✅

You only use am (an dem) with specific days or dates as nouns:

am Montag (on Monday)
am 3. Mai (on May 3rd)
am Wochenende (on the weekend)

But:

gestern, heute, morgen → no preposition, no article.

How would the sentence change in the plural (for multiple laptops)?

Plural changes:

mein → meine
alter → alten (plural adjective ending)
Laptop → Laptops
ist → sind (plural auxiliary)

So:

Meine alten Laptops sind gestern kaputtgegangen.
= My old laptops broke yesterday.

Structure stays the same; only agreement (possessive, adjective, noun, verb) changes to plural.

Is there any difference between kaputtgegangen and other words like defekt or zerbrochen?

Yes, there are nuance differences:

kaputtgegangen
- verb form (Perfekt of kaputtgehen)
- commonly used for devices or things that stop working / break down
- Mein Laptop ist kaputtgegangen.
kaputt (adjective)
- state: broken, often casually
- Mein Laptop ist kaputt.
defekt (adjective)
- more technical/formal: faulty, defective
- Der Laptop ist defekt. (e.g. in a repair shop, on a sign)
zerbrochen (participle of zerbrechen)
- usually for things that physically break into pieces (glass, cups, etc.)
- Das Glas ist zerbrochen.

For an electronic device that just stops functioning, kaputtgegangen is the natural choice.