Carbon NMR spectroscopy produces a spectrum of only carbon-13 nuclei in a sample. The number of carbon signals in the spectrum corresponds to the number of in the molecule. In most carbon NMR spectra, the carbon signals appear as singlet peaks .

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.