What's the difference between 'open' and 'open up' here?

Question

We usually say:

I'm open to new experiences

and not 'open up'.

why is that?

Answer 1

In the sentence

I'm open to new experiences.

"open" is an adjective, modifying "am", or one might better say that "open to new experiences." is an adjectival phrase.

"Open up" is a phrasal verb. It can be an instruction, as in:

Open up, this is the police!

Or it can be declarative. For example

• I want you to open up to me, so that I understand your feelings.

• I am ready to open up to new expereinces.

In this form it often takes an indirect object after "to", although this can be omitted. For example:

I was tired of keeping secrets. i just wanted to open up.

It can als be used in a less metaphorical way, such as:

I saw the ground open up and a car fall in.

"Open up" is a present tense form, but can be used with both past and future events, through auxiliary verbs to set the tense.

Answer 2

"Open up" is an instruction. In the sentence

I'm open to new experiences.

you are already open. Last week perhaps you could have said

I hope to open up to new experiences.

(I'm not sure how to describe the difference in formal grammatical terms. I'm trying to answer the OP's question as to why the first sentence sounds wrong with "open up".)