Independent Variable: It is the substances used on the mild steel. The substances used were water, vinegar, and ammonia. The role played by these substances is if we change the substance we change the outcome of the experiment.

Dependent Variable:  It is what the substance does to the mild steel. That is what we are testing to see what will happen if we apply acids and bases (the substances) to mild steel.

Control Variables:

Ø    size of nail

Ø    condition of nail

Ø    kind of nail

Ø    how wet the paper  towel is

Ø    length of time in paper towel

Ø    temperature of room

Ø    humidity of room

Ø    how long the nails are out of paper towel         

 Ø  substance used on nails

Ø    air flow in the room

Ø    temperature of substance

Ø    purity of the substance

Ø    how old the substance is

Ø    the amount of air hitting the nail