On your list you can easily identify by knowing which is not a chemical change.
A physical change is a change not involving the material composition of the water. e.g. (melting, solidifying, evaporation). As long as the change does not change the molecular composition of the water which is H20 it is physical change.
C. The Uniformity of Cosmic Background Radiation
A. A control group is given the experimental treatment.
Answer: 5 m
Explanation:
We have the following data:
is the intensity of the sound at 7.5 m from the source
is the distance at which the intensity 
was measured
is the intensity of the sound at 
from the source
We have to find
Since the object is radiating the signal uniformly in all directions, we can use the <u>Inverse Square Law for Intensity:</u>
Isolating :
This is the distance at which the intensity is the "threshold of pain"
Now, we have to substract this value to 
to find how much closer to the source can we move:
The genotype for all offspring will be Pp making the flower color white.
