Ions carry the current
Acid and base solutions carry electricity because they hold ions.
The bulb test
A bulb is connected to a battery and two electrodes. The electrodes dip into a liquid. If current flows through the liquid, the bulb glows.
Which liquid will make the bulb glow?
What this lesson covers
The idea
Acidic and basic solutions in water conduct electricity because they contain ions, which carry the electric current through the solution.
The bulb test
A bulb is connected to a battery and two electrodes. The electrodes dip into a liquid. If current flows through the liquid, the bulb glows.
Which liquid will make the bulb glow?
- Hydrochloric acid solution
- Glucose solution
- Alcohol solution
Switch on
A teacher sets up the circuit with dilute solutions. Test every liquid: switch on and look at the bulb and at the particles in the liquid.
Ions carry the current
Acidic and basic solutions in water conduct electricity because they contain ions, which carry the electric current through the solution.
Glucose and alcohol have hydrogen too, but they do not make ions. So they do not behave like acids.
- Liquid | Bulb | Particles
- Acid solution (HCl, H₂SO₄) | glows | ions
- Base solution (NaOH) | glows | ions
- Glucose, alcohol | dark | no ions
Notes
Acidic and basic solutions in water conduct electricity because they contain ions, which carry the electric current through the solution.
Check yourself
Why does the bulb glow with HCl solution?
Which solution will not light the bulb?
What carries the electric current through an acid solution?
A solution makes the bulb glow. We can say that the solution …
- The solution is hot. Heat is not the reason. Ions carry the current.
- The solution has glucose in it. Glucose does not carry current.
- The ions in the solution carry the current — correct. Yes!
- Glucose solution — correct. Yes! It has no ions.
- Dilute sulphuric acid. An acid solution has ions, so the bulb glows.
- Sodium hydroxide solution. A base solution has ions, so the bulb glows.
- Sugar molecules. Neutral molecules cannot carry a current. Ions can.
- Ions — correct. Yes!
- The glass beaker. The current flows through the liquid, carried by ions.
- contains only molecules. Molecules alone cannot carry a current.
- is always an acid. Bases also make the bulb glow. We can only say it has ions.
- contains ions — correct. Yes!