A/a physical change is when an object goes through a natural change such as weather etc.
B/ the different is that 1) chemical change is more quick to change rather than physical (ex: I’d there is rocks flying around and is wearing down another rock it would take longer rather than acid)
The type of substances that would make good conductors would be substances that has greater density. This would mean that the particles of the substance are much closer to each other and would allow the free flow of the electrons in the substance. With this, current would be able to flow freely.
There are 70 atoms in 5CaC12