At what pH value is a substance considered acidic?

A substance is considered acidic when its pH is less than 7. The pH scale ranges from 0 to 14, where values below 7 indicate acidity, values of exactly 7 indicate neutrality, and values above 7 indicate alkalinity (or basicity).

When the pH is below 7, it means there is a higher concentration of hydrogen ions (H+) compared to hydroxide ions (OH-). This is characteristic of acidic substances such as vinegar or lemon juice, which have pH values considerably lower than 7. The lower the pH number, the stronger the acid typically is, meaning that a substance with a pH of 5 is more acidic than one with a pH of 6.

Thus, any substance that has a pH less than 7 is classified as acidic, confirming that this choice appropriately reflects the criteria for acidity in the context of the pH scale.