Im not positive but i think it is When it is a gas?
Methane
CH₄
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1- physical
2-chemical
3-Physical
4-Chemical
5-I’m not sure
I haven’t done this in a while so these may be wrong sorry
When a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more lighter nuclei, (the fission products), releasing kinetic energy, gamma radiation, and freeneutrons