Are the following physical or chemical changes?

1. weathering:
2. deposition:
3. metamorphism:
4. melting:

How does a nuclear reactor produce electricity? a. high-energy gamma rays are converted by a generator into electricity. b. the heat from the reaction turns water to steam, which runs a generator. c. the reaction produces a stream of electrons that flow through wires and into batteries. d. the heat released from the reaction is used to burn coal or gas to produce electricity. e. control rods absorb the neutrons emitted and release a stream of electrons as electricity.