Describe a characteristic of a fissionable substance that is essential for a chain-reaction to sustain itself.

The fissionable substance that is essential for a chain reaction in order to sustain itself shows that atomic mass needs to be heavier for it to release more than one neutron. Because of this reaction it is expected to release some energy.

plasma is the state of matter where the substance is ionized and has no definite shape or volume. the fact of being ionized makes the substance a good electrical conductor.

i'm wiling to try and you : )