International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

How can you determine if a liquid is an electrolyte?

1. By measuring its temperature

2. By putting it in a circuit with an ammeter

3. By putting it in a circuit including a bulb

4. By observing its viscosity

The correct answer is: By putting it in a circuit including a bulb

To determine if a liquid is an electrolyte, one effective method is to put it in a circuit including a bulb. Electrolytes are substances that dissociate into ions when dissolved in water, allowing them to conduct electricity. When such a liquid is included in a circuit with a light bulb, the flow of electric current can cause the bulb to light up. If the bulb lights up, it indicates that ions are present and can move through the liquid, confirming that the liquid is indeed an electrolyte. This method directly tests the electrical conductivity of the liquid, which is a key characteristic of electrolytes. In contrast, measuring the temperature may not provide relevant information about the liquid's electrolytic properties. Using an ammeter alone can measure current but does not provide a visual confirmation like a bulb. Observing viscosity does not correlate with the presence or absence of ions, as viscosity primarily relates to the flow characteristics of a liquid rather than its conductivity.