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

The answer is d-- A is melting and B is sublimation.

Explanation:

A is melting because a solid is changing into a fluid and B is sublimation because a solid changing straight into a gas.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

fe 55.85 g/mol and h2o 18.02 g/mol.