- Acids have pH less than 7 and produce H⁺ ions in solution
- Alkalis have pH greater than 7 and produce OH⁻ ions in solution
- Neutral substances have pH exactly 7 (equal H⁺ and OH⁻)
- Universal indicator shows a range of colours across the pH scale
- Litmus is red in acid, blue in alkali
- Phenolphthalein is colourless in acid, pink in alkali
- Methyl orange is red in acid, yellow in alkali
- The three common lab acids are: HCl, H₂SO₄, HNO₃
- The two common lab alkalis are: NaOH, KOH
- Concentrated = lots of acid/alkali particles per volume
- Dilute = few acid/alkali particles per volume
This key facts covers Key Facts: Acids, Alkalis and Indicators within Acids and Alkalis for GCSE Chemistry. Revise Acids and Alkalis in Chemical Changes for GCSE Chemistry with 25 exam-style questions and 21 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 7 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Acids and Alkalis
Which ion do acids produce when dissolved in water?
Explain the difference between a strong acid and a concentrated acid.
Quick recall flashcards
Name two common alkalis
Sodium hydroxide (NaOH), Potassium hydroxide (KOH)
What is universal indicator?
An indicator that shows a range of colours across the pH scale (rainbow of colours from red to purple)