An irreversible change would be? A. chipping ice to flakes
B. getting a hair cut
C. condensing steam
D. boiling water

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?

A40 kilogram skier starts at the top of a 12 meter high slope. at the bottom, she is travelling 10 meters per second. how much energy does she lose to friction

Which of the four hypothetical substances you investigated would be most harmful to living organisms? 50 points!