Question

acids have ph ____ than 7, bases have ph ____ than 7. higher, lower lower, higher

Explanation:

The pH scale ranges from 0 - 14. Acids have a higher concentration of hydrogen ions ($H^+$) and thus have a pH lower than 7. Bases have a lower concentration of hydrogen ions and a higher concentration of hydroxide ions ($OH^-$), resulting in a pH higher than 7.

Answer:

lower, higher