Isothermal process

Imagine you have a toy balloon filled with air. Now, put the balloon in the fridge. After some time, you'll notice that the balloon seems to have become smaller in size. This is because the air particles inside the balloon have lost some of their energy and have slowed down, causing the balloon to deflate. The process by which the balloon cools down (loses heat) and gets smaller in size is called an isothermal process.

So, an isothermal process is a process where the temperature of a system remains constant while some other property, such as pressure or volume, is changed. In other words, during an isothermal process, the energy in the system remains constant, but the system changes in other ways.

For example, when you boil water in a pressure cooker, the temperature of the water and the pressure inside the cooker remain constant, but the volume of the steam that forms inside the cooker increases. This increase in volume happens because the energy from the heat makes the water particles move faster, and they push against the walls of the pressure cooker, increasing the pressure inside. As a result, the volume of the steam increases (even though the temperature remains the same).

In summary, an isothermal process is when the temperature of a system remains constant while some other property (such as pressure or volume) changes. It's like when you put a balloon in the fridge and it gets smaller - the temperature stays the same, but the size changes.