Why can two clear liquids cancel each other out?
You can mix an acid and a base, and instead of getting something “extra strong,” you can end up much closer to plain water. That happens because the key particles from each solution remove each other.
When you use the Arrhenius idea, you treat substances in water by the ions they make.
An acid is a substance that, once dissolved in water, increases the amount of H⁺(aq).
A base is a substance that, in water, increases the amount of OH⁻(aq).
If you zoom in one level deeper, the Brønsted–Lowry model is about proton transfer.
You call something an acid when it gives away a proton, H⁺, during a reaction.
You call something a base when it takes in a proton, H⁺, from something else.
In your MYP work, you’ll usually use the water-based Arrhenius picture for solutions and the proton-transfer picture when you explain what particles are doing.
Think of it like your phone battery and a charger cable. One side is supplying what the other side needs. In acid–base reactions, the “thing being passed” is H⁺, not electricity.
A really useful surprise is that water itself can play both roles.
A substance is amphiprotic if it can either donate H⁺ or accept H⁺ depending on what it reacts with.
Water can hand over a proton to a stronger base, or grab a proton from a stronger acid.
In water, acids and bases show up through ions. Hydrochloric acid separates like this:
Sodium hydroxide separates like this:
Those H⁺ ions are why acidic solutions have low pH and react in familiar ways. Those OH⁻ ions are why alkaline solutions have high pH and can cancel acids.
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