Boxi Learn › Chemistry › Stage 4 · Systems and Argument
Adding base: the pH jump at the end
CHEM-1 Atoms are rearranged, never lostX-1 Guess, then checkX-2 Evidence outweighs opinion
What many people think
Each drop of base raises the pH by about the same amount, so the pH climbs steadily to 7.
The idea
H⁺ and OH⁻ pair into water one for one, so the pH barely moves until the counts are almost equal, then a single drop pushes it up several units.
Explain it
A friend adds 20 mL of base, sees the pH go only from 1.0 to about 2, and decides the base is too weak. Explain what is really happening, using the H⁺ that is left.
Try at home
Count out 1000 grains of rice as H⁺. Take away 900 (now 100 left: one pH step), then 90 (10 left: another step), then 9 (1 left: another). Each step removes less than the last; the next step would need you to remove a fraction of one grain. That last tiny amount is the single drop.