Final answer:
The dependent variable in Mrs. Gaubert's experiment is the time it takes for rust to form or the extent of rust on the nail when immersed in different liquids. Rust forms due to the chemical reaction of iron with oxygen to create iron (III) oxide, requiring both water and oxygen.
Step-by-step explanation:
In Mrs. Gaubert's experiment to determine which type of liquid would make a nail rust the fastest in a month, the dependent variable is the time it takes for the nail to rust or the extent of rusting that occurs. This is the outcome that she is measuring in each of the different liquids, which are Coke, Water, Gatorade, and Milk.
The reaction that occurs during the rusting of an iron nail can be represented by the chemical equation: Fe + O₂ → Fe₂O₃, where iron reacts with the oxygen to form iron (III) oxide, commonly known as rust. The presence of both oxygen and water is necessary for this reaction to occur, which means the different liquids will provide varying conditions that may affect the rate of rust formation.
For example, water is a key component for rusting to occur, whereas in organic solvents that lack water, such as kerosene, rusting would not occur despite the presence of oxygen.