If you test grapefruit juice and find it has a pH of around 3, what does this indicate about its acidity compared to water?

A pH of 3 means the grapefruit juice is highly acidic, because the pH scale runs from 0 to 14 and lower numbers are more acidic. Water has a neutral pH of 7, so the juice is four units lower, which corresponds to a 10,000‑fold higher concentration of hydrogen ions. In other words, the juice is ten thousand times more acidic than water. For example, if you had 1 mL of water and 1 mL of grapefruit juice, the juice would contain about 10,000 times more acidity than the water. This shows that grapefruit juice is very acidic compared to neutral water.