Answer:
from fast-moving to slow-moving particles during particle collisions.
Explanation:
The molecules in every substance are constantly in random motion, which is called thermal motion. This means that they continuously move in random directions with random velocities. In particular, their speed depends on the temperature of the substance: the higher the temperature, the higher the average kinetic energy of the particles, the higher their speed.
However, not all particles move with same speed: some of them move faster, some of them move slower.
Since there are many particles, quite often these particles collide with each other: in the collision, energy is transferred from one particle to another.
In conduction, which is one of the 3 methods of heat transfer (the other 2 being conduction and radiation), the heat is transferred via collision between the molecules.
In particular, according to the laws of thermodynamics, energy is always transferred from particles moving faster (which have therefore more energy) to particles moving slower (which have therefore less energy).
So the correct answer is
from fast-moving to slow-moving particles during particle collisions.
