Learn Hardcore Dutch: Anna morst soep op haar nieuwe blouse.

morst is the present tense, third-person singular of the verb morsen. It corresponds to English “spills” or “is spilling.” Dutch often uses the simple present to describe ongoing actions (similar to the English present continuous).

What does morsen mean and how is it different from knoeien?

morsen means “to spill” (especially liquids) in a neutral sense.
knoeien can also mean “to spill,” but it more broadly means “to make a mess,” “to tamper,” or “to botch something,” often carrying a negative or careless connotation.

Why is there no article before haar nieuwe blouse?

When you use a possessive pronoun (like haar) in Dutch, you omit the article. So haar nieuwe blouse literally means “her new blouse.”
If you weren’t using a possessive, you’d say:

een nieuwe blouse (“a new blouse”)
de nieuwe blouse (“the new blouse”)

Why is it nieuwe blouse and not nieuw blouse?

In Dutch, adjectives preceding a noun get an -e ending when the noun is:
• a common‐gender noun with a definite article or possessive pronoun (like haar)
• a plural noun
Since blouse is a common‐gender noun (de‐word) and we have haar, the adjective takes -e: nieuwe blouse.

What does the preposition op indicate here? Why not over or in?

op indicates movement onto a surface, like “onto.”

Anna morst soep op haar nieuwe blouse = “Anna spills soup onto her new blouse.”
in would mean “into” (inside the blouse).
over implies “all over” (covering), so over haar blouse changes the nuance to “all over her blouse.”

Why does the verb morst come directly after Anna? How does Dutch word order work?

Dutch is a V2 (verb-second) language: the finite verb must occupy the second position in the sentence.
Here:
1) Anna (first position)
2) morst (verb in second position)
3) soep and op haar nieuwe blouse (the remainder)
If you place another element first (time, place, etc.), the verb still remains in the second slot.