How can one measure the mass change of nails in an experiment on rusting?

To measure the mass change of nails in an experiment on rusting, using a balance scale is the appropriate method. This instrument allows for precise measurement of mass, enabling the experimenter to determine the initial weight of the nails before the rusting process occurs and then measure the weight again after a certain period. The difference in mass will indicate how much rust has formed as a result of the reaction between the iron in the nails and the oxygen in the environment, aided by moisture.

Other options are unsuitable for this specific measurement: a thermometer measures temperature, which does not directly relate to mass; a measuring tape is used for length rather than weight; and a pH meter measures the acidity of a solution, which is also not relevant to the mass of the nails. Thus, using a balance scale is essential for obtaining accurate measurements needed to analyze the rusting process.