What happens when a substance undergoes a physical change?
Some physical properties change, but the substace keeps its identity.
No physical properties change, and the substance keeps its identity.
Some physical properties change, and the substance changes its identity.
No physical properties change, but the substance changes its identity.

The picture represents the process that produces most of the energy used by living organisms on earth. which process is represented in the picture? a) the magnetic attraction between two hydrogen nuclei. b) the fusion of hydrogen nuclei to produce a helium nucleus in the core of the sun. c) the fission of hydrogen nuclei to produce a helium nucleus in the core of the sun. d) the chemical reaction between hydrogen nuclei to produce a helium nucleus in earth's atmosphere.