Question

read the experiment below and answer the next four questions. a scientist wants to know what happens to limestone when it is exposed to acid rain. the scientist gets two limestone rocks of the same mass. one rock is soaked in acid rain but the other rock is soaked in distilled water. both containers with rocks are left outside. after one week, the scientist weighed the mass of each rock. which of these is a control variable? * 1 point rock soaking in acid rain rock soaking in distilled water starting mass of the rocks mass of the rocks after soaking

Explanation:

A control variable is kept the same in an experiment to ensure that only the independent variable (type of water - acid rain or distilled water) affects the dependent variable (mass of rock after soaking). The starting mass of the rocks is made equal for both samples, so it is a control variable. The rock soaking in acid rain is the experimental group, the rock in distilled water is the control group, and the mass after soaking is the measured outcome.

Answer:

C. Starting mass of the rocks