Calmly explain there is much to do in this class and to get to do the fun stuff I will need you complete attention. Have the students follow along with the top chart in their guides. Acids have a pH less than 7. Put your finger on the 7. The strongest acid has a pH near 0.
Most fruits are acids.
It is normal that most fruits are acids, it keeps them from spoiling as quick. 14 is the strongest alkaline. Drain cleaner is almost that strong. The closer the pH is the 7 the less strong the alkaline. Sometimes it may help to compare temperature to pH using cold, hot and comfortable.