pH
In chemistry, pH is a logarithmic scale used to specify the acidity or basicity of aqueous solutions.
Also known as: pH value
At a glance
Key signals
0% cross fields · reaches 1 more
- Chemistry
- Explanation
- Examples
- Misconception 2
- Sourced relations 3
- Attribution
Structural role & consequence
Interpreted from the current atlas graph — what the connections mean, not just how many there are.
Currently dark in the atlas: no key date stored · 1 of 3 of its relations lack claim-level evidence.
atlas representation · Describes the current Thinking OS representation, not the state of the world.
Structural neighbourhood: 3 → 8 → 19 concepts reachable within 3 hops.
structural · Structural reach — being reachable is not the same as being understood.
All 3 of its relationships stay within its own discipline — a field-specific concept in the current atlas.
structural · Structural graph analysis — not a claim of importance, causation or history.
cross-field
3 within-field, 0 cross-field
Strengths & constraints
Strengths
- Well-evidenced in the atlas — a verified source and 67% of its relations carry claim-level evidence. atlas representation
Constraints
- No dated history stored — the atlas records no key date for this concept. atlas representation
Seen through each discipline
How this concept sits in each of its fields — derived from its real connections in the graph, not asserted.
Through this lens it connects to Acid, Base and Buffer solution.
Formula
Source: Wikidata
What it looks like
Concrete cases that make this idea recognisable in the real world.
Stomach acid vs lemon juice
Lemon juice near pH 2 is about 100 times more acidic than black coffee near pH 4 — two pH units means two factors of ten, not 'twice as sour'.
Check yourself
A quick check against a common misconception. Nothing is scored — picking the tempting-but-wrong answer just flags an idea worth revisiting.
Which statement is correct?
Which statement is correct?
A pH of 4 is just a little more acidic than a pH of 5.
The pH scale is logarithmic, so pH 4 is ten times more acidic than pH 5. Small pH differences mean large changes in acidity.
Look for: Learner reads pH steps as equal, linear amounts.
pH 5 is just a bit more acidic than pH 6, and pH 7 is always neutral.
pH is logarithmic: each unit is a tenfold change in hydrogen-ion concentration, so pH 5 is ten times more acidic than pH 6. And exact neutrality is 7 only at 25 °C — the neutral point shifts with temperature.
Related ideas to explore
Concepts that look related but are not yet connected here — candidates for a connection to reason about, not established links.
This idea also appears in…
The same structure shows up in other disciplines. These are real recurrences drawn from the graph — a starting point for asking “what carries over, and what changes?”
Scale32 disciplines · 42 concepts
Concepts
shares a mental model
shares a mental model
shares a mental model
shares a mental model
shares a mental model
shares a mental model
pH is a scale from 0 to 14 that says how acidic or basic something is. Below 7 is acidic (like lemon juice), 7 is neutral (pure water), above 7 is basic (like soap). It's measured with indicator paper or a meter.
pH is the negative logarithm of the hydrogen-ion concentration, pH = −log[H⁺]. Because it is logarithmic, each unit is a tenfold change: pH 3 is ten times more acidic than pH 4 and a hundred times more than pH 5.
Mental models at work here
- Connects 3 other ideas across 1 discipline.
- Most of its connections are of the “Explains & models” kind.
- It exercises 1 reusable thinking pattern.
Derived from the graph’s real structure — observations, not a score.
Sources
- Wikipedia (English & German editions) verifiedmoderate evidence
- Wikidata verifiedmoderate evidence
- Chemistry 2e (OpenStax) (2019) verifiedmoderate evidence