What can thermal energy can be transferred I conduction from one piece of matter to another only if the two pieces are

Correct and complete question:

Thermal energy can be transferred by conduction from one piece of matter to another only if the two pieces are.

liquids touching solids fuel

Answer:

Touching

Explanation:

Thermal energy is also known as the internal energy of a system. The system is comprised of atoms that are always in moving condition. If the internal energy of the system is low, the movement would be slow and so the thermal energy would be lesser; however, if the movement of atoms is faster, then the thermal energy is higher. In a situation where thermal energy is needed to transfer by conduction from one piece of matter to the other, they should come in contact. Here, moving atoms in high thermal energy system (material) will collide to the other material (system) and transfer their kinetic energy. This process will continue until both system are touched and they reach equilibrium.

It doesn't matter if the solution is liquid or solid, or fuel because movement of atoms would take place in all materials (for some it will be slower and for other it will be faster).