The Scientific Method

The Scientific Method

Introduction

Chemists use the scientific method in order to develop a better understanding of matter. The first step of the scientific method is to state the problem to be studied. The second step is to form a hypothesis, which is a prediction of the outcome of an experiment. Thirdly, an experiment is designed and performed with the purpose of confirming the hypothesis. Lastly, qualitative and quantitative data are collected and analyzed, which often leads to the revision of the hypothesis, followed by a new experiment.

This cyclical process usually involves many experiments. Experiments are repeated to ensure reproducible results. Reproducible behaviors that are observed may become scientific law. Consider the reaction of hydrogen with oxygen to form water, according to the equation, 2 H2 + O2 → 2 H2O. Many experiments were conducted when mass ratios of 4.0 grams of hydrogen react with 32.0 grams of oxygen. The data consistently showed that 36.0 grams of water are produced. Notice that the total mass of the reactants is identical to the mass of the products. Experiments were repeated with other reactions, and the results showed the total mass of the reactants is identical to the mass of the products. These observations of behavior led to the law of conservation of mass. A law permits the prediction of results based on previous behavior. A theory explains the reasons for the behavior.

This activity will provide you with the opportunity to practice utilizing the scientific method and to develop your critical thinking and analysis skills.

Objective

In this activity, you will develop an experimental procedure to solve a problem. Consider the following scenario:

You are the manager of a chemical stockroom, and find a bottle containing approximately one liter of a clear and colorless solution of unknown identity and concentration. Your only clue to its identity is that it was found between bottles of silver fluoride and sodium fluoride, so it is likely an aqueous solution of one of those two compounds. You will need to develop a procedure to determine the following:

1. a)  The identity of the unknown solution
2. b)  The concentration of the unknown solution

Write out a precise procedure, which includes all glassware, reagents, and steps. You will also need to write the calculations that you would need to determine the concentration of the solution. Assume that you have access to any reagent you might need. You may also assume that you have access to common laboratory equipment. You observed some examples of laboratory equipment within the Virtual Chemistry Laboratory simulations. You may visit the virtual lab at chemcollective.org to refamiliarize yourself with this equipment or to try out some techniques. To complete this assignment, consider both the techniques learned in the lab simulations and the information learned in lecture.

Your report should be written in Microsoft Word or a similar word processing program. Please be certain to include the following sections:

Title of Experiment
Note: the title of your experiment should not be “The Scientific Method.” Instead, you should give your procedure a title that reflects the objectives of your experiment.

Materials and Reagents
In this section, list the glassware you will need, including sizes, as well as any chemical reagent you might need for your analysis.

Procedure
This should include numbered step-by-step instructions for how to perform your analysis. It should be written in such a way that a fellow CHEM 131 student with similar lab skills can perform it exactly. Be certain to be precise and unambiguous with your language. Specify any data that needs to be collected during the procedure. Note any observations that would lead the experimenter to know the identity of the solute.

Calculations
Provide the equations and calculations necessary to determine the concentration of unknown solution. You may provide a set of sample calculations.

Discussion
Use this space to clarify any details from your procedure and describe your thought process. Be certain to address specifically how to tell one solute from another and the reason you would expect different results depending on the identity of the solute.

Julie@chegg.com