This is possible because in a solid the atoms and molecules are constrained to fixed position called lattice sites . Their thermal vibrations pass heat energy along to other nearby molecules, and thus heat is transferred from the hot end of the solid substance to the cooler end. Warm fluids expand and rise because their density becomes less than the density of the rest of the surrounding fluid. The hottest portion of the heated fluid then rises, causing convection loops to form, by means of which the circulating fluid carries heat energy to other parts of the fluid. Winds on the surface of Earth are also driven by complex and powerful convection processes within the atmosphere.
Radiation can take place through any transparent medium.
You may have noticed how radiated heat from a campfire can be felt when it is transferred through the air to your body if you are standing close enough to the fire. The actual heat transfer is made by a form of electromagnetic waves called infrared radiation . In solids, the atoms or molecules are constrained to lattice sites. This explains the basic properties of a solid, such as rigidity, constant shape, and constant volume. The atoms and molecules in a liquid, however, are free to move around each other, although the distance between the molecules remains about the same.