Final answer:
When the pH of a glass of orange juice decreases, it becomes more acidic as a result of a higher concentration of hydronium ions.
Step-by-step explanation:
As the pH of a glass of OJ decreases, it becomes more acidic. The pH scale is used to measure how acidic or basic a solution is. A pH less than 7 indicates an acidic solution. The more acidic a solution is, the lower its pH value will be. This is because an increase in the concentration of hydronium ions ([H3O+]) corresponds to a more acidic solution and thus a decrease in pH value.