pH scale and universal indicator solution
I can measure the pH of an acid or alkali using the pH scale.
- Year 9
pH scale and universal indicator solution
I can measure the pH of an acid or alkali using the pH scale.
Lesson details
Key learning 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.
- 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.
Keywords
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 misconception
The difference between concentrated and dilute vs strong and weak when referring to acids and alkalis (not covered in this lesson).
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).
Equipment
Universal indicator paper or solution, test tubes, test tube racks, plastic pipettes, spotting tiles, indicator charts.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Match the keyword to the correct statement
Q2.Which of these statements about chemical reactions are true?
Q3.What is the result if blue litmus paper is dipped into lemon juice?
Q4.What is the result if red litmus paper is dipped into soapy water?
Q5.True or false? Vinegar can be used to neutralise sodium hydroxide.
Q6.Which containers of liquid may require a corrosive hazard label?
Assessment exit quiz
6 Questions
Q1.Match the keyword to the correct statement.
