Lesson Plan: The pH Scale Chemistry • 7th Grade

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to define pH as a logarithmic measure of acid concentration and use it to determine the relative acidity or basicity of a substance.


Students will be able to

  • recall that pH is a relative measure of acidity and basicity,
  • define pH in qualitative terms as a logarithmic measure of the concentration of H+ ions,
  • draw and interpret a pH scale including common acids and bases,
  • identify acids and bases from their pH values,
  • estimate the pH values of common acids and bases (e.g., lemon juice),
  • understand and explain the change in pH during an experiment (e.g., adding powdered calcium hydroxide to dilute hydrochloric acid),
  • describe the use of simple indicators to provide an approximation of the pH of a solution (e.g., litmus paper, universal indicators).


Students should already be familiar with

  • acidity and basicity.


Students will not cover

  • quantitative descriptions of pH,
  • calculations of pH,
  • the relationship between pH, pKa, and other dissociative constants.

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