Question

does particles of matter become denser on increasing the temperature?

Answer 1

We never find the density of particle but we explain the density of system or medium or substance.
The density of a substance is defined as the mass per unit volume of the substance.We can also say that it is the amount of matter in unit volume of a substance. As the temperature increases, the kinetic energy of molecules increases results in increase in movements of particles. As the molecular movements increases, it will create more spaces in between the molecules and hence the mass per unit volume decreases and density also decreases.