When heat energy is added, two changes are observed: change a: solid changes to a liquid. change b: solid changes directly to a gas. what are the names for phase changes a and b?
a-- a is freezing and b is condensation.
b--a is freezing and b is sublimation.
c-- a is melting and b is condensation.
d--a is melting and b is sublimation.
the answer is d