Question

Suna passes an electric current through a sample of clear, colorless, and odorless liquid. As the experiment continues, bubbles form, and the volume of liquid decreases. Suna collects samples of two colorless, odorless gases that bubble out of the liquid. One of the gases burns. Neither the original liquid nor the other gas burns.

Which is the best explanation of her results?

The electric current changed some of the sample to gas even though the sample was not breaking down. Therefore, the original liquid is a compound.
The electric current released a gas that was odorless and colorless, like the original sample. Therefore, the original liquid is an element.
The sample was broken down by the electric current and formed a new substance that could burn. Therefore, the original liquid is a compound.
The sample lost some of its volume, but the gas still had the same chemical makeup as the original sample. Therefore, the original liquid is an element.

Answer 1

The best explanation is: "The sample was broken down by the electric current and formed a new substance that could burn. Therefore, the original liquid is a compound."

Reason: Passing current through the liquid caused electrolysis, which decomposed the compound into two different gases (e.g., hydrogen, which burns, and oxygen, which is colorless/odorless and supports burning). Elements cannot be broken down into simpler substances by chemical means, so the original substance must have been a compound (like water).