For dilute aqueous solutions near 25°C, neutral pH is approximately 7. Acids and bases shift the balance of hydrogen and hydroxide ions. An indicator responds to its chemical environment by changing its own molecular form and colour. This schematic uses an illustrative colour scale rather than promising that every indicator produces the same colours at every pH.
Matter and chemistry · Discover & try
What can an indicator tell us about a solution?
Reading level 3 of 5 · IndependentChange
Word help
pH
A logarithmic quantity related to hydrogen-ion activity.
indicator
A substance whose appearance responds to chemical conditions.
Watch · Try · Explain
See how it works
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Virtual room-temperature pH with an illustrative indicator palette; no tasting, mixing or handling of real chemicals.
What to look for
- Neutral is near 7 under these conditions
- Lower and higher values differ
- Indicator palettes are not universal
Explain what you noticed
Two virtual solutions have pH 6 and pH 8 near 25°C. How are they classified?
Keep this idea: Compare pH with the stated neutral point; colour is a clue, not a safety verdict.
Follow the sources
- American Chemical Society — pH and Color Change
- American Chemical Society — Neutralizing Acids and Bases
Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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