Which best describes the purpose of a controlled experiment?

A controlled experiment is an experimental setup designed to test the hypotheses. It has one or more conditions (independent variables) and measures (dependent variables). It is necessary to change more than one variable, but all of the experimental conditions will be controlled so that only the variables being examined change and the amount or way of change is measured.  

Explanation:

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a controlled experiment is an experiment that you have 100% controll of so if something goes wrong you can controll it easily unlike an uncontrolled experiment that can turn out to be very dangerous.

Explanation:

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a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.