A soft keyboard (sometimes called an onscreen keyboard or software keyboard) is a system that replaces the hardware keyboard on a computing device with an on-screen image map.
An ideal gas is defined as one in which all collisions between atoms or molecules are perfectly eleastic and in which there are no intermolecular attractive forces. One can visualize it as a collection of perfectly hard spheres which collide but which otherwise do not interact with each other.
A Non-Ideal Gas â We noted above that the ideal gas law holds for low-density gases. In theoretically deriving the ideal gas law it is necessary to make two assumptions -- the gas molecules are very small (they have no volume) and the molecules are non-interacting (there is no force between them). In 1873 the Dutch physicist van der Waals derived an equation of state without these assumptions.