iMac 27" 2017 5K needs more space and memory

Memory (RAM) and storage space / drive space are different things.

RAM is a fast working area that the processor needs. It loses all of its contents whenever you reset the computer or turn the power off.

It sounds like with your photos, you are running out of internal and external storage space - not out of RAM. Certain types of advanced photo processing can be demanding on RAM, but that is a separate issue.

Sounds like you need to make a plan on what to move to an external hard drive, and possibly need to buy a larger external hard drive.

Photos, videos, music, movies, TV shows, and high-end games are the usual culprits when it comes to devouring hard drive space like so much cotton candy.

Your problem is not that it doesn't have adequate RAM. Even with 8GB of RAM Chrome should launch unless there is something else wrong.

However in order for us to tell what may be causing your problem we need to know what has been installed on it and more information about the Mac itself. Please do the following and so we can help you out.

It will help us get a good idea of what is causing your problem if you provide a report of your system, that way we do not have to play 20 questions with you. The report we are requesting does NOT provide any personal information and is extremely safe to use. Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click How to use the Add Text Feature When Post… - Apple Community It is helpful to us if you download the report to your Desktop.

You can add or change memory yourself. You can buy from Crucial online however not sure your issue is with memory. The issue of not being able to open an app does not have to do with memory. How much hard drive space do you have? You probably have some other issues. You can run the free app Etrecheck and post here for review.