Recall that scientists use a systematic approach called the scientific method to discover knowledge about the natural world. The scientific method is based on making and testing hypotheses. A hypothesis is a tentative and testable statement that must be capable of being supported or not supported by observations. An experiment is a scientific investigation that is made to test the validity of a hypothesis.
An experiment usually has three identifiable types of variables. An independent variable is a variable that is specifically changed by the scientist in the experiment. A dependent variable is a variable that is measured in the experiment or that which can change in response to the independent variable selected. Control variables are sometimes called scientific constants. These are all other factors that could influence the results of the experiment, but they are kept constant, or unchanged, to rule out their effect.
Scientific experiments are performed under controlled conditions--that is, under conditions in which a single variable changes. This is to make sure a scientist can identify the exact cause of the relationship.
In this lesson, you will plan and conduct an experiment to gather evidence about the solubility or surface tension of a substance and relate it to the forces between particles of the substance.
Question
At the end of this lesson, you will plan and conduct a controlled experiment. What is a controlled experiment?
In a controlled experiment, only one independent variable is deliberately changed at a time.
A scientist goes about problem solving in an orderly manner, trying to determine the effect of a particular factor. A scientist sets up a controlled experiment to test the effect of a particular factor on something else. A controlled experiment attempts to test only one factor at a time. Scientific thinking attempts to isolate what factor causes something to happen and what happens or changes as a result of that factor.
