Question

finn noticed that he could make a dome of water on a penny if he added drops of water slowly enough. he wondered if adding soap to the water would allow him to fit more or less water on the penny. finn put equal - sized drops of pure water, one at a time, onto a penny. he recorded the number of drops he could add before the water spilled over the edge of the penny. then, he rinsed and dried the penny, and repeated the test using water mixed with hand soap. finn repeated these trials on seven additional pennies.
a dome of water on the surface of a penny
complete the sentence.
in this experiment, the pennies with pure water were part of ______.

a control group
an experimental group

Explanation:

In an experiment, a control group is used as a standard for comparison. Here, the pennies with pure water are the control because they are not exposed to the variable (soap) being tested, while the pennies with soapy water are the experimental group. So the pennies with pure water are part of the control group.

Answer:

a control group