can i put hot soup in mason jar for travel
I have had mason jars break when filling with hot items.  It is best to warm the jar first, just by running hot water into it.  A someone else pointed out, a mason jar is, of course, not insulated.  You mention this is to take to work, I assume for lunch or dinner.  I also want to point out that you need to consider food safety, as your soup will soon be in the "danger zone."  You should read this.  It is much safer to chill the soup to refrigeration temperature, pack it in a cooler, or refrigerate at work, then reheat at meal time.