A scientific control is an experiment or observation designed to minimize the effects of variables other than the independent variable.
Answer: The new pressure is 3 psi.
Explanation:
Given:
= 12 psi, 
= ?, 
Formula used is as follows.

Thus, we can conclude that the new pressure is 3 psi.
Answer:
the newspaper one is a chemical change because the chemicals in the paper have reacted with something and turned a different color. the wax one is a physical change because it is a change in the phase of matter, which is always a physical change (still the same substance chemically)
1 property
2 procedure
Results
The correct name for the N3- ion is a nitride ion.