Semipermeable means the cell membrane can pick and choose what goes out of it and into it. At least, that's what I believe it is.
Answer:
pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic. Since pH can be affected by chemicals in the water, pH is an important indicator of water that is changing chemically.
