A laboratory experiment is a method of testing a hypothesis. The specific procedure can vary greatly, but an experiment must be repeatable. The results of a good laboratory experiment must also be subject to significant analysis.
Overview
The scientific process begins with an observation that results in the scientist asking a question. The scientist proposes a possible answer to this question, which is known as a hypothesis. An experiment is the part of the scientific process that allows the scientist to identify the best hypothesis of two or more competing hypotheses. The results of a laboratory experiment will ideally favor one hypothesis over the others, no matter what the results are. An experiment can never disprove a hypothesis; it can only add support for the hypothesis. However, a single counterexample can disprove the hypothesis.
Quantitative Experiments
A quantitative experiment focuses on the measurement of some quantity. Galileo Galilei was one of the first scientists to perform quantitative experiments, including the speed of falling bodies. Galileo accurately measured the time needed for objects to fall from different heights. These experiments were used to disprove Aristotle’s assertion that the speed of the object was affected by its weight. This experiment was successful because Galileo could measure the time of the object’s fall with unprecedented accuracy by using a pendulum. Algebra was a new branch of mathematics at the time, which allowed him to describe the relationship between the height of the object and the time needed for the object to reach the ground.
Chemistry
Antoine Lavoisier performed some of the earliest laboratory experiments in chemistry during the late 18th century. These experiments established that matter is neither created nor destroyed during a chemical reaction. Lavoisier burned phosphorus and sulfur in the presence of air within a sealed container. While the weight of the solid material increased after the reaction, the total weight of the container’s contents did not change. This result added support for the hypothesis, which became known as the Law of Conservation of Mass.
Biology
Some of the first laboratory experiments in biology were performed by Louis Pasteur during the 19th century. Scientists of this era generally believed that bacteria appear spontaneously from nonliving matter. Pasteur disproved this idea by showing that bacteria would not grow on a medium unless existing bacteria could reach the medium.