A control group is the comparison group that helps to "make sure your experiment works." A control group is separated from the rest of the experiment and nothing happens to it kinda like a controlled variable. Controlled variables are the variables in a experiment that remains the same for example a temperature, time, type of products, etc..
Hope this helps!
The pH of pure water is 7.0, which is neutral.
For a pH below this, the water is acidic. Substances that are acidic are often corrosive and thus could cause weather damaging. The pH of the precipitation in NY is below that of the precipitation in IL, and NY receives more precipitation, so for both of those reasons, it is likely to have more chemical weathering.
A weak acid has a low concentration of H+ Ions and a dilute acid is a solution where acid is dissolved in a more volume of water than that of acid.
