Why are experimental investigations the best type of scientific investigation to demonstrate cause-and-effect relationships?

: Experimental investigations are the best type of scientific investigation to demonstrate cause-and-effect relationships because they allow the investigator to actively manipulate variables and control conditions. The independent variable can be isolated and manipulated, producing a change (or no change) in the dependent variable. This change can be measured to gather evidence to support or refute the cause-and-effect relationship. Experimental investigations also use a control group (a group that does not receive the factor being tested) for comparison.

Copper, silver, aluminum, cobalt, chromium, mercury 

Iwould you figure it out but you don't have a picture or in your question as to what the physical property you're looking for is