Hi, I am going to teach a class of year 9 students on the topic "Thermal Properties of Matter" and the concept of Internal Energy is mentioned inside. As I was trying to anticipate the types of questions that will be asked by them, this question suddenly struck me: Is there a limit to the internal energy of a system? As far as the syllabus is concerned, Internal energy = Kinetic energy (KE) + Potential energy (PE). So, I am thinking: Once the matter reaches the gaseous state, can we continue to increase the KE and is there a limit to it? Thank you! P.S.: Feel free to add in extra information as they will be helpful for me to answer any questions from the students and improve my knowledge.