When dry ice heats up, it turns into a gas. Is that a chemical or physical change?

Achange in the number of neutrons in an atom will change an blank . when the number of protons changes in an atom, a new element will form.

Select all of the methods through which a drug can enter your body. injection swallowing inhalation absorption

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?