: Litmus paper is a basic indicator but cannot determine exact pH values; for precise measurements, use a pH meter .

Understanding circuits is a major part of the 2B curriculum.

: In a simple buzzer circuit, energy typically transforms from chemical energy (cell) →right arrow electrical energy →right arrow sound energy . Unit 9: Acids and Alkalis

Assignments cover using the pH scale and natural indicators, such as red cabbage extract, which turns red in acids and green in alkalis. Unit 10: Sensing the Environment

Leo looked at the answer key in his hands at home that evening. He realized the truth. The answer key didn't know the context. It didn't know Mr. Harrison had changed the elements. It didn't know the specific focus of the lesson.