Grade 7 Science: Acids and Bases

Substances may also be classified into acids and bases. In the laboratory, we identified which common household substances are acidic or basic by using blue and red litmus paper.

acid base indicator

We tested the following substances:

  • toothpaste
  • vinegar
  • calamansi
  • detergent powder
  • chlorine
  • soda

The substances were dissolved in water. Blue and red litmus paper were dipped in each of the solutions. After which, pH paper was used to determine the specific pH of each substance.


  1. What happened to each strip of litmus paper dipped in each solution?
  2. Which solutions can be grouped together based on your observations on the litmus paper?
  3. What properties to the substances grouped together have in common?
  4. What does the number on the pH meter indicate?

Here is a presentation that can be used in discussing acids and bases as well as the neutralizations process:


You may also find more information about acids and bases on this site: Acids and Bases

As an extension activity, students will be asked to produce their own acid-base indicator using plant extracts. They will also be asked to devise and experiment that will put their indicator to test.


Ariel Lalisan

Ariel Lalisan

Ariel Lalisan is a physics teacher at Alabel National Science High School. He is an advocate of constructivism approach in education. He employs active learning and independent learning in his lessons, and, of course, a lot of technology integration. His goal is to produce students who can solve problems on their own using the concepts they learn in the classroom. Ariel Lalisan is a Google Certified Innovator (Google Teachers Academy Southeast Asia 2014) and a community leader at Google Educator Group Sarangani. He is a co-founder of SoCCSKSarGen and he won the Globe Media Excellence Blogger of the Year Award in 2015.

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