Unequal amounts make a liquid acidic or basic/ alkaline.
Acids are substances that donate H+ ions to the solution:
Bases are substances that donate OH- ions to the solution:
The pH scale is a logarithmic scale. So, for every "1" on the scale, it's really a power of 10. A four is 10 times more acidic than a 5, 100 times more than 6, and 1,000 times more than 7.
|Equations graphics used from: www.all-about-ph.com|