Why the conjugations of verb Estar are used with food-items like sopa está caliente
I've been taught to use the conjugations of estar with the temporary state of things.
The usage of
estar (because it's a auxiliar verb, as
haber) is quite different than the other verbs.
Estar it is common useful to express a quality that has been changed as a result of another action. In your case, the soup is hot because has been heated.
For more information about different usages take a look at: