Which energy transformation occurs when an
electrolytic cell is in operation?
(1) chemical energy → electrical energy
(2) electrical energy → chemical energy
(3) light energy → heat energy
(4) light energy → chemical energy

Compare and contrast physical changes with chemical changes.

Calculate the number of kilojoules to warm 125 g of iron from 23.5°c to 78.0°c.

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?