Deep Dive: What Actually Makes an Acid?
This deep dive covers Deep Dive: What Actually Makes an Acid? 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 2 of 12 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 2 of 12
Practice
25 questions
Recall
21 flashcards
🔬 Deep Dive: What Actually Makes an Acid?
When an acid dissolves in water, it releases hydrogen ions (H⁺) into the solution. These tiny, positively charged particles are what make acids behave the way they do — they are responsible for the sour taste of citric acid, the corrosive nature of concentrated acids, and the reactions with metals and carbonates. The more H⁺ ions in a solution, the more acidic it is and the lower the pH.
Think of an acid as a "hydrogen ion donor". When you dissolve it in water, it breaks apart and releases H⁺. The water molecules play an essential role — without water, acids cannot fully ionise or show their acidic properties. That is why pure (anhydrous) acids are far less reactive than their aqueous solutions.
The key equations:
Hydrochloric acid: HCl → H⁺ + Cl⁻
Sulfuric acid: H₂SO₄ → 2H⁺ + SO₄²⁻
Nitric acid: HNO₃ → H⁺ + NO₃⁻
Alkalis are the opposite: they release hydroxide ions (OH⁻) when dissolved in water.
Sodium hydroxide: NaOH → Na⁺ + OH⁻
Potassium hydroxide: KOH → K⁺ + OH⁻
Remember: An alkali is a base that dissolves in water. All alkalis are bases, but not all bases are alkalis (e.g., copper oxide is a base but doesn't dissolve).
Keep building this topic
Read this section alongside the surrounding pages in Acids and Alkalis. That gives you the full topic sequence instead of a single isolated revision point.
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
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