// FIELD GUIDE 03 — LEVEL L1–L2
Acids, bases, and the pH scale
Lemon juice stings a paper cut. Soap feels slippery. Both are chemistry — just opposite ends of the same scale. Slide through it below.
// L1 — TWO OPPOSITE FAMILIES
Acids taste sour, react with metals, and turn litmus paper red. Alkalis (bases dissolved in water) feel soapy, turn litmus blue, and neutralise acids. Vinegar and lemon juice are acids you've tasted; soap and oven cleaner are alkalis you've touched.
// L2 — WHAT pH ACTUALLY MEASURES
Every acid releases H⁺ ions in water; every alkali releases OH⁻ ions. pH just counts how many H⁺ ions are floating around — low pH means loads of them (acidic), high pH means hardly any (alkaline), and pH 7 is the perfect balance (neutral, like pure water). Each step on the scale is ten times more concentrated than the last — pH 4 has 10× more H⁺ than pH 5.
// L2 — NEUTRALISATION (INTERACTIVE)
Mix an acid and an alkali and their ions cancel out: an H⁺ from the acid grabs an OH⁻ from the alkali to make plain water, while the leftover ions stay behind as a dissolved salt. Add alkali to the acid below, drop by drop, and watch the H⁺ ions disappear.
// FIG. 04 — HCl + NaOH → NaCl + H₂O
H⁺ — from the acid
OH⁻ — from the alkali
H₂O — water made
Na⁺ & Cl⁻ — the salt
+ ADD ACID (H⁺)
+ ADD ALKALI (OH⁻)
RESET
{{ verdict }}
pH ≈ {{ nPh }}
free H⁺: {{ freeH }} · free OH⁻: {{ freeOH }} · H₂O made: {{ waterCount }}
Once every H⁺ has paired with an OH⁻, only water and the dissolved salt (Na⁺ and Cl⁻) are left — that's neutral. It's the same reaction that lets a bee-sting cream (alkaline) soothe a sting (acidic), and lets farmers spread lime (alkaline) on acidic soil.
// REFERENCES & FURTHER READING
Cross-check against your own exam board's specification (AQA, Edexcel, OCR, SQA).