Science
Matter & Materials
Conceptual
12–13 yrs
Acids, Alkalis & pH
酸、碱与pH值
Description
Define acids and alkalis in terms of hydrogen ion concentration, describe the pH scale (0–14), and explain how indicators are used to identify and measure acidity or alkalinity
Mastery Evidence
- States that acids have pH below 7, alkalis have pH above 7, and neutral is pH 7
- Explains what hydrogen ions (H⁺) have to do with acidity
- Names common indicators (litmus, universal indicator) and describes colour changes
- Identifies everyday acids (vinegar, lemon juice) and alkalis (bleach, bicarbonate of soda)
Assessment Prompt
If your child used a piece of universal indicator paper to test lemon juice and baking soda solution, could they predict what colour each would turn and explain what that tells you about each substance?
