Which observation most likely indicates that only a chemical change has taken place? the change cannot be reversed.
the shape changes.
states of matter changes.
a reaction occurs.

Which type of orbits are found in the principal energy level n = 2 a - s b - s, f c - s, d d - s, p e - s, p, d

There are main groups in the modern periodic table of elements

Which process does not require the presence of a physical substance in order to transfer heat? air in the atmosphere is heated by the ground. this warm air then rises, and cooler air falls. this is an example of what type of process? how is conduction different from radiation?