The document summarizes key concepts about acids and bases: - The pH scale measures how acidic or alkaline a substance is from 0-14. Phenolphthalein and bromothymol blue are acid-base indicators that change color. Universal indicator can be used to test unknown solutions and determine pH. - Strong acids have a pH of 0-1 and strong bases 13-14. Acids contain hydrogen ions and bases contain hydroxide ions. Examples of acidic foods are citrus fruits and milk. Cleaners are often bases. - Acids taste sour and pure water is neutral. Stronger acids have lower pH numbers. The pH range of normal rain is 5.6-6.