In the context of the kinetic theory of gases, the notion that a molecule of gas could have zero kinetic energy, even momentarily, while changing direction upon collision with the wall of the container is improbable. According to the kinetic theory, gas molecules are in constant, random motion and collide with each other and the walls of the container. These collisions are considered to be elastic, meaning that kinetic energy is conserved before and after the collision.

Kinetic energy (KE) for a particle is given by the formula:

Where $m$ is the mass of the particle and $v$ is its velocity.

• For a particle to have zero kinetic energy, its velocity would have to be zero ($v=0$).
• If a molecule were to momentarily stop moving (i.e., $v=0$) upon a collision, this would violate the principles of elastic collisions as outlined in the kinetic theory, because kinetic energy would not be conserved.
• In a perfectly elastic collision, both momentum and kinetic energy are conserved.
• In a real-world scenario, any deviation from this is usually because some of the energy is converted into other forms such as heat, vibration, or sound, but in the idealised model of kinetic theory, these are not factors.

Moreover, in statistical mechanics, it is understood that the velocities of particles in a system follow a distribution, commonly modelled by the Maxwell-Boltzmann distribution in classical gases. According to this distribution, the probability of finding a particle with zero velocity is effectively zero. Even if we consider quantum gases, the Heisenberg Uncertainty Principle prevents both the position and the momentum (and hence the kinetic energy) of a particle from being simultaneously zero.

Therefore, within the framework of kinetic theory and our current understanding of physics, it is not possible for a gas molecule to have zero kinetic energy when it is changing direction upon colliding with the wall of the container.