For an observer who stays in one spot when the source of a sound is moving,

the sound wave's:

O

A. frequency changes.

O

B. amplitude decreases.

O

C. speed increases.

O

D. amplitude increases.

3. how much energy in joules is required to evaporate .0005 kg of liquid ammonia to vapor at the same temperature? 4. how much energy ( in megajoules ) is given up by .75 kg of water at 0c when it freezes to form ice at 0c? 5. explain how heat works between and at critical temperatures?