Heat conduction is a heat transfer phenomenon when there is no macroscopic motion in the medium, which can occur in solids, liquids and gases, but strictly speaking, only in solids is pure heat conduction, in fluids (generally refers to liquids and gases) In another case, even if the fluid is in a static state, natural convection will occur due to the density difference caused by the temperature gradient
thermal convection and heat conduction may occur simultaneously in the fluid.
One end of the iron rod is placed in hot water, and the temperature of the other end increases