Hey, is there any difference between "apart" and "separately"? For example:

Please say each word apart.
Please say each word separately.

When they are apart they behave differently.
When they are separately they behave differently.

Question

Hey, is there any difference between "apart" and "separately"? For example:

Please say each word apart.
Please say each word separately.

When they are apart they behave differently.
When they are separately they behave differently.

Answer

They are not the same. Say each word separately. When they are apart. Those are correct. The others are not.

Apart means to be physically away from something.  It’s a state of being. 
Separately always goes with an action: do, say, work.

It’s easier to count (action) separately when we are apart (state of being).

Answer

Hello I have a hunch you meant to say "break ing apart words" which just means dividing words into sylables/ prefixes +word+ suffixes.

starfish   star+fish

On the other hand saying a word separately means reading each word one at a time.

I (pause) like(pause) starfish.

Answer

Hey Rafal!

Both words can be used in a variety of contexts, so it's hard to concisely express when one word is more fitting than the other. Here’s how to use them in your sentences ;

Please say each word separately.

AND

When they are apart they behave differently.
When they are separate they behave differently.

However, there are times when the two words could be used pretty much interchangeably: The hermit lived separate/apart from everyone else. And another example is your second sentence.

Hope this helps