Asubstance that could be separated into two or more substances only by a chemical change is a(n)

Compound  

Explanation:

A compound is a substance that can be separated into two or more substances only by a chemical change.

For example, water is a compound.

We can separate it into hydrogen and oxygen by electrolysis.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.

there is none because earth is stationary and flat.