CH141 Laboratory

 

Name

CH141 Lab Section

Date

Partner

 

Report for Experiment 1 – Scientific Measurements and Introduction to Excel

 

Use complete sentences, use the proper number of digits and/or significant figures, and include units. Erase all the words in italics and type your answers/information into this template (your text/answers shouldn’t be in italics).

 

Over the semester, we will build up to writing full lab reports that include the following sections: Introduction, Procedure, Results, and Discussion/Conclusions. For Experiment 1, you will only add the reference in the Procedure section, and supply the requested information in the Results and Discussion sections.

 

Introduction: 2-sentence maximum; state the scientific purpose of the experiment. Describe the method you will use, in a general sense. Do not discuss the experimental procedure details or data analysis steps. We wrote the Introduction section for you this week . No additions are necessary.

 

The percent composition of pennies was determined by measuring the masses and volumes of zinc and copper samples as well as the pennies themselves. Excel was used to calculate sample densities and percent composition of the pennies.

 

Procedure : Give a brief description of the experimental procedure. Reference the experiment handout on the CH141 website. List any changes from the written procedure (if any). No other additions are necessary.

 

Densities calculated by mass and volume measurements were used to determine the percent composition of zinc and copper in pennies . [1]

 

Results : In future reports, you will supply full (raw) data in tabular form in this section, as well calculated quantities and graphs. For this week, you only need to include what is specifically asked for below. Table “templates” are included below if you wish to use them.

 

Remember to use proper number of digits and/or significant figures and include units. Please erase the bullets from the list below when you erase the italicized words. All tables and figures should be numbered and have a caption.

 

         Include a clearly labeled table of your data for % copper and density. Please provide an informative but succinct title.

         Include a graph of density verses % copper. The graph should occupy no more than half of a page and include a title, labeled axes that include units, and the linear regression curve fit results, with the appropriate number of significant figures. The graph should have a descriptive caption (no more than three or four lines, but less is fine).

         In tabular form, include your LINEST data for the graph of density vs. % copper.

         Mention any student errors that may have caused problems in the determinations. Include only actual errors that you made (not a list of possible errors). Hopefully there will be no such errors!

 

Percent Cu, %

Density of Cu/Zn composite (g/mL)

0

 

10

 

20

 

etc.

 

 

Table 1:  Write a table caption

 

 

Slope

Y-intercept

Value

 

 

Error

 

 

R 2

 

 

 

Table 2:  Write a table caption

 

Discussion For this report, you will not write a full Discussion but instead answer the following questions. On future reports you will be asked for more complete analysis and discussion. When citing results r efer to each Table/Figure with an explicit reference as necessary (e.g. see Table 1) in the relevant part of this section.

 

1. Look at your data (measurements) that you used to calculate the densities of copper, zinc and pennies. Suggest at least two sources of error that affected the accuracy/precision of your measurements. For each source of error: a) indicate whether it is systematic or random, b) briefly explain why you chose that type of error, and c) briefly describe how it affected your results (be as specific as possible)

 

2. In a sentence or two, compare the literature value for the % copper in a penny to your experimental value. To determine the accuracy of your measurement you can use the following formula (don’t show the calculation in your report, just report/discuss the result)

 

Percent accuracy = 100 - |literature value – experimental value|*100

  literature value                                          

 

What do you think was the limiting factor (specific type of error) in the accuracy of your value?              

 

3. In no more than three sentences, clearly explain how your group results inform you about designing experiments to make accurate/precise scientific measurements.              

 

Attachments:

 

Attach copies of your (three) Excel data tables for the calculation of the density of Cu, Zn, and the pennies. Please include captions on your attachments (these can be hand written). The tables should include the average, standard deviation, standard deviation of the mean, and % error of the trials – remember to refer to these data tables to answer your Discussion questions!


[1] This footnote should reference your lab handout from the website.