Question: Can you explain the difference between an object that is hot and the same object when it was cold - without using the word Temperature?
The most important point is this:
All objects have more energy when they are hotter.
We know this because: Hot objects can do things that they could not do when they were cold.
For instance, hot objects can cause other objects to become warmer (think radiator or cooker), they can glow (emit visible radiation), they can cause another object to melt or boil, they can cook eggs, etc..
So what? Well, being able to do more is the simplest definition of having more energy.