When you add thermal energy to a substance, it affects it in various ways, even without causing a change of state. Here's a breakdown:

Impact on Kinetic Energy:

• Directly Increases Kinetic Energy: The main effect is directly increasing the kinetic energy of the individual particles, be it atoms or molecules, within the substance. Imagine tiny balls representing the particles. Adding thermal energy is like giving them a push, making them move faster and vibrate more intensely.
• Temperature and Kinetic Energy Relation: Remember, temperature itself isn't the energy but rather a measure of the average kinetic energy of the particles. So, adding thermal energy raises the average and, consequently, the temperature.

Effects without State Change:

• Increased Particle Movement: Even if the substance stays solid, liquid, or gas, the increased kinetic energy translates to more active movement. In solids, the particles vibrate more within their fixed positions. In liquids, they flow more freely. In gases, they collide more frequently and rapidly.
• Expansion: Thermal expansion is a common effect. As particles move faster, they take up more space, causing the overall volume of the substance to expand. This is why metals expand when heated (think train tracks) and liquids fill more of their container.
• Increased Diffusion: The faster movement also leads to enhanced diffusion, where particles spread out and mix more readily. This plays a role in various processes like cooking, dissolving, and chemical reactions.
• Increased Internal Energy: Thermal energy adds to the substance's overall internal energy, even if the temperature doesn't necessarily change significantly. This internal energy can then be used for other processes, like driving chemical reactions or phase changes later.

Further Points:

• Material Specifics: The effect of adding thermal energy can vary depending on the material's specific properties. For example, water has a high specific heat capacity, meaning it requires more energy to raise its temperature compared to other materials like metals.
• Limited Expansion: Even without a state change, expansion has limits. If confined, the added energy might convert to other forms, like increasing the internal pressure or even causing structural changes.

Overall, adding thermal energy, even without inducing a phase change, significantly affects the behavior and properties of substances, primarily by increasing the kinetic energy of their constituent particles.

Dr Murtadha Shukur thank you for your contribution to the discussion