PENNIES OVER TIME

CLASS DATA is HERE!
You will need to save it to your disk and open it with Excel.
Or, if you are using QuatroPro, download this format for the CLASS DATA.

INTRODUCTION

Scientists acquire knowledge by following a systematic procedure called the Scientific Method. The Scientific Method involves several steps. The first step is a statement of the question to be answered in a particular investigation, referred to as the purpose of the investigation. The next step is to collect data. This is accomplished by making careful observations specifically designed to answer the question asked in the Purpose. Such observations are called experiments. The data or results of the experiments are then interpreted and a conclusion is drawn from them. Ideally, the conclusion contains the answer to the question asked in the purpose. A tentative explanation of the results or hypothesis is then formulated. The hypothesis is then tested by performing further experiments. Once a hypothesis has been verified repeatedly by experimentation it becomes the basis for a theory. A theory is a unifying principle that explains a body of facts.

Click here, for an extension of these ideas to the laboratory notebook. Note, that in this course the word "experiment" is used in two ways: it refers to the observations used to obtain data within a scientific investigation. It also refers to the overall investigation, which itself consists of four parts: purpose, procedure, results and conclusion.

Purpose

The purpose of today's experiment is to illustrate the Scientific Method and to give you some experience in performing some common laboratory operations. The experiment will involve the measurement of the masses and volumes of pennies of different mint dates.

The purpose of Part 1 is to answer the question, "does the mass of a penny vary with the mint date?" Data will be collected to answer this question. You will then be asked to formulate at least two hypotheses to explain your results. In Part 2, you will perform experiments to test your hypotheses.

Procedure

Part 1: Obtain a sample of 30 pennies from the Stockroom. Weigh each one to 0.001 g, measure its diameter and thickness in cm, with calipers. For each penny record these data and the mint date.

To combine your data with that of the other honor student, promptly send it to Dr. Stone via Email (koni@chem.csustan.edu). In the body of the email message, list the date and weight separated by a comma. 

e.g.:

1952, 2.452
1968, 2.543

This data will be available as an Excel file that you can download from this page.  When the browser asks you what to do with the file, just save it to your disk.  Once you have the class data, make a graphs to analyze it.  You may to manipulate the data (i.e. calculations) to answer the questions asked in the purpose.

You will also need to analyze the data for statistical significance.   Directions for calculating averages and standard deviations can be found here.  Be sure to use your class data and not the file that is located on the "statistics" page.

Use your results to draw a conclusion which answers the question asked in the purpose.

Formulate at least two hypotheses to explain your results. For example, if the penny masses do show a variation with mint date, what are some possible reasons for this variation? A review of intensive and extensive properties might be helpful at this point: Click here.

Part 2: Test two of your hypotheses. this may be accomplished by further interpretation of the data obtained in Part 1 or by doing more experiments.

In your notebook, write up each of the two tests as separate experiments, containing a purpose, procedure, results and conclusion. Note that the hypothesis becomes the purpose of the experiment.

Part 3: Do your results in Part 2 provide any information about the kind of metal found in pennies?  What metals are present in pennies?   Have all pennies been minted with the same composition?  Do pennies wear out?