Enough kinetic and proper orientation are the two
requirements for the collision to form a product.

The  grandmother cell  is a hypothetical  neuronthat represents a complex but specific concept or object.[1]  it activates when a person "sees, hears, or otherwise sensibly discriminates"[2]  a specific entity, such as his or her grandmother. the term was in use at least as early as 1966 amongst staff and students in the department of experimental psychology, university of cambridge, england. a similar concept, that of the  gnostic neuron, was proposed two years later

Density and pressure

No. an alpha particle is a pair of protons and a pair of neutrons, i.e. a helium