The source of power in a nuclear power plant comes from a) burning hydrogen atoms. b) reacting uranium atoms. c) splitting uranium nuclei. d) combining hydrogen nuclei.

C) splitting uranium nuclei

Explanation:

Nuclear energy is the energy that is obtained by manipulating the internal structure of atoms, usually useful to produce electricity.

This type of energy can be obtained by nuclear fusion and by nuclear fission:

So, the source of power in a nuclear power plant comes from splitting uranium nuclei, since when a nuclear fission (or a nuclear fusion) occurs, the atoms experience a slight loss of mass, which becomes a large amount of heat energy.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.