The four states of matter all have different density. A way to compare the states of matter would be by density. The density of a small solid would be more than the density of a liquid of the same amount because of how close the particles are. Solids are the most dense and then liquids, gasses, and plasma. Another way to compare them is by there Kinetic energy. Kinetic energy is measured by the amount of motion. Plasma has the most Kinetic energy then gas, liquid, and solid.
Conduction is the transfer of heat through solids. Convection is the transfer of heat though liquids and gasses.