Year 9 - Science
pH scale and universal indicator solution
Acids and bases
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit covers acids, alkalis, and their neutralisation reactions, the pH scale, and the reactions of acids with metals and alkalis. It also examines the chemical properties of metal and non-metal oxides. Emphasis is on evaluating risks, using appropriate techniques, and making observations.
Lesson Summary
You will learn to measure the pH of an acid or alkali using the pH scale.
Key Notes
- Most acids and alkalis are colourless solutions, so indicators can be used to identify them.
- pH stands for 'potential of hydrogen' and acids contain hydrogen.
- The higher the concentration of hydrogen, the lower the pH.
- The pH scale goes up and down in factors of ten, so an acid of pH 2 is ten times more acidic than pH 3.
- A low pH means acidic, a high pH means alkaline and solutions with a pH of 7 are neutral.
Vocabulary To Learn
- pH scale: A scale from 1 to 14 used to measure the acidity or alkalinity of solutions. pH7 is for neutral solutions.
- acidic: A solution that has a pH of less than 7.
- alkaline: A solution that has a pH of more than 7.
- neutral solution: A solution that has a pH of 7.
- concentration: The amount of chemical dissolved in a certain volume of solution.
Common Mistakes To Avoid
- The difference between concentrated and dilute vs strong and weak when referring to acids and alkalis (not covered in this lesson).
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
Most acids and alkalis are colourless solutions, so indicators can be used to identify them. pH stands for 'potential of hydrogen' and acids contain hydrogen.
2. Define this scientific word and use it in context. 'pH scale'
A scale from 1 to 14 used to measure the acidity or alkalinity of solutions. pH7 is for neutral solutions. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: The difference between concentrated and dilute vs strong and weak when referring to acids and alkalis (not covered in this lesson). Correction: For acids and alkalis concentration is the amount of hydrogen dissolved in a certain volume of solution. The higher the concentration, the lower the pH. Strong and weak refer to the ability of an acid to release hydrogen (not covered in lesson).
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