True or false..
(A) Burning of magnesium ribbon is physical change

Compare and contrast the bohr model and the electron cloud models of the atom.

Which of the following is an indication that a substance has undergone a chemical change? a. no new product has been formed. b. the color of the substance has not changed. c. the original constitute has not changed. d. the molecular structure has changed.

Draw the aromatic compound toluene (methylbenzene). show all hydrogen atoms, including those on the ring.