# A lesson designed to guide you through the process of composing a suitable lab report

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A lesson designed to guide you through the process of composing a suitable lab report. Report Writing Guide. Overview. - PowerPoint PPT Presentation

### Transcript of A lesson designed to guide you through the process of composing a suitable lab report

Week 2*

A lesson designed to guide you through the process of composing a suitable lab report

Report Writing Guide

GenChem

Overview

This lesson will review the process you need to use to compose a proper report. Each section of the report is covered separately. The experiment covered is the first experiment performed this semester. For each section you will be presented with the questions you need to ask yourself as you compose your report.

GenChem

Section Order

The order in which the sections of the report should be composed is not the same as the order of the finished report.

Order of Sections in Report

Introduction

Procedures

Results

Calculation

Discussion

What were the major goals of today’s lab?

Determine the wavelength of maximal absorbance (λmax).

Determine the molar absorptivity at λmax ().

GenChem

Introduction

From p. 65 of your Technique Book:

Introduction. A description of what is already known, the plan of action and expected outcomes.

From p. 71 of your Technique Book:

Introduction. A description of:

Question to ask yourself:

For each goal, list the major techniques, formulas, and chemicals used:

λmax

Calipers- path length

Introduction: Goal 1

In a paragraph, introduce Goal 1. Include all items on your list.

Introduce Goal 1. Define λmax and give expected outcomes.

Plan of action. How was Goal 1 achieved? Introduce techniques/formulas/chemicals in context.

Relevance of results. What can you do with your newly found λmax?

GenChem

Introduction: Goal 1

*

Introduction: Goal 2

In a paragraph, introduce Goal 2. Include all items on your list.

Introduce Goal 2. Define ε and give expected outcomes.

Plan of action. How was Goal 2 achieved? Introduce techniques/formulas/chemicals in context.

Relevance of results. What can you do with your newly found ε?

GenChem

Introduction: Goal 2

Goal 2 was to find ε for the assigned dye. ε is a measure of how strongly a substance absorbs light at a particular wavelength and is a large value for dark colorful substances. In Beer’s Law, ε is the proportionality constant that relates absorbance to concentration (A=εbC).

To determine ε, Absorption Spectroscopy was used to measure absorbance values (at the λmax) of several dilutions of dye with known concentrations. An Excel graph of A vs. C was generated so slope=εb. The slope was given by the Excel trend line and the path length (b) of the cuvette was measured with calipers. ε can be used to determine the concentration of food dye in unknown solutions.

GenChem

Introduction

The first goal was to determine the λmax of the assigned food dye. The λmax of a substance is the wavelength of light with the highest absorbance and is the wavelength opposite the color seen by the human eye. The λmax was determined using Absorption Spectroscopy, a technique that measures the wavelengths of light absorbed by a colored solution. The λmax was then used to conduct a Beer’s Law analysis in Goal 2.

Goal 2 was to find ε for the assigned dye. ε is a measure of how strongly a substance absorbs light at a particular wavelength and is a large value for dark colorful substances. In Beer’s Law, ε is the proportionality constant that relates absorbance to concentration (A=εbC).

To determine ε, Absorption Spectroscopy was used to measure absorbance values (at the λmax) of several dilutions of dye with known concentrations. An Excel graph of A vs. C was generated so slope=εb. The slope was given by the Excel trend line and the path length (b) of the cuvette was measured with calipers. ε can be used to determine the concentration of food dye in unknown solutions.

GenChem

Introduction: Helpful hints

Only include information that is known before lab. No results, observations, etc.

200 word maximum for one week lab.

Paragraph format. Subheadings okay.

Give items in context. No lists.

See Technique Book pp. 65, 67 and 71 for more help with writing an Introduction

See Technique Book pp. 52-55 for more help with scientific writing.

GenChem

Procedures

Also known as “experimental”. This section will be discussed with the next report.

GenChem

Calculations

Calculations. Examples of all calculations performed to manipulate the numerical data. Include one example for each type.

From p. 70 of your Technique Book:

One example for each type of calculation. Each example should consist of three parts:

The formula that describes the calculation

The formula in use

Question to ask yourself:

For each goal identify the important calculations that should be included.

Determine λmax

Determine at λmax.

Calculation of a value for .

GenChem

Calculations

Your presentation of your calculations should always use a three step format:

Write out the equation

Plug in your numbers

Give the answer

This method ensures that your instructor can follow your thought process during the calculation.

Do not forget to add units and watch significant figures during your calculations!

GenChem

Calculations: Goal 1

For a dilution the product of the concentration times the volume is constant.

C1V1 = C2V2

C2 = 5.37 x 10-5 M

*

Calculations: Goal 2

The first calculation of goal 2 is the same as that of goal 1: dilution. Since we have already shown this calculation, we do not need to show it again.

If we calculated the concentration a different way, then we would need to show a second calculation.

GenChem

Calculations: Goal 2

The second calculation we have listed is density. We obtained this value from the graph, but it would be helpful to make a note in the calculations so that the reader does not think you forgot one:

Density of known plastic: Determined from the slope of the graph

GenChem

Calculations: Helpful Hints

Include a calculation for all types of calculations that you do, but only include one example for the type of calculation

Watch significant figures and units

GenChem

Results

From p. 65 of your Technique Book:

Results. An organized presentation of the observations and calculated results. This section is frequently dominated by figures, tables and graphs. It will contain little to no text.

From pp. 67-8 of your Technique Book:

Results. An objective and clear description of experimental findings following an appropriate order and including relevant:

Tables

Graphs

Figures

GenChem

Question to ask yourself:

For each goal identify the important results and supporting data that should be included.

Determine λmax

Calculation of a value for .

GenChem

Results: Goal 1

Sometimes, it makes more sense to list numbers and answers in a clear order rather than putting them in a table.

Dye: Indigo carmine

λmax : 610 nm

Figure 1: Visible-UV spectrum of indigo carmine

GenChem

Results: Goal 2

For repetitive and/or related data a labeled table is best. Compile all of the items on your list in a logical order.

Table 1. absorbance of standard solutions

* Ratio of stock solution volume to final solution volume

** absorbance values measured at 610 nm

Dilution*

Results: Goal 2

It is often a good idea to display this information in a graph as well. If we plot the absorbance on the x-axis and the concentration on the y-axis, the slope will be the molar absorptivity of the dye.

Graph 1. absorbance vs concentration of standard food dye solutions.

at 610 nm = 5.50 x 105 abs/cmM

*

Results: Helpful Hints

Only include results that are important to the conclusions that you make

Be careful about the amount of significant figures you have, especially when copying tables that you’ve made from Excel

GenChem

Discussion

From your Technique Book:

Discussion. Analysis of the data and presentation of conclusions regarding original hypothesis. This should include a defense of the conclusions citing the results and a discussion of the reliability of the data used.

GenChem

What does it mean?

Does it make sense?

Is it consistent with your observations?

Comparisons to literature or peers.

If something went wrong: What were you expecting and why? What went wrong? How do you know? How could you fix it next time?

GenChem

Discussion: Goals

The λmax of Blue #1 was 610 nm which lies in the orange region of the visible light spectrum. As expected, the orange color absorbed is opposite the blue color observed.

Using the λmax, the ε for Blue #1 was found to be 55,000 M-1cm-1. This is a larger ε than the other three dyes, which means Blue #1 is the best at absorbing light. This is consistent with the observation that Blue #1 had the darkest appearance out of the four dyes.

GenChem

Discussion: Data quality

In a paragraph, discuss the quality and reliability of your data:

Discuss pros/cons/accuracy/precision of tools/techniques.

Be specific and give examples.

Suggest fixes for the problems you identify and additional experiments to improve findings.

Avoid discussing general human error. Only specific, documented errors should be addressed.

GenChem

Discussion: Data quality

The λmax value seems reliable because the spectrometer gives readings that vary by a maximum of 1 nm. Also, 610 nm is an exact match to the class average λmax. The ε value also came close to the class average ε of 55,000 M-1cm-1. The calipers used to measure the path length are accurate to 0.01 cm and the volumetric kit used for dilutions measures volumes accurate to 0.01 mL.

*

GenChem

Discussion

A lesson designed to guide you through the process of composing a suitable lab report

Report Writing Guide

GenChem

Overview

This lesson will review the process you need to use to compose a proper report. Each section of the report is covered separately. The experiment covered is the first experiment performed this semester. For each section you will be presented with the questions you need to ask yourself as you compose your report.

GenChem

Section Order

The order in which the sections of the report should be composed is not the same as the order of the finished report.

Order of Sections in Report

Introduction

Procedures

Results

Calculation

Discussion

What were the major goals of today’s lab?

Determine the wavelength of maximal absorbance (λmax).

Determine the molar absorptivity at λmax ().

GenChem

Introduction

From p. 65 of your Technique Book:

Introduction. A description of what is already known, the plan of action and expected outcomes.

From p. 71 of your Technique Book:

Introduction. A description of:

Question to ask yourself:

For each goal, list the major techniques, formulas, and chemicals used:

λmax

Calipers- path length

Introduction: Goal 1

In a paragraph, introduce Goal 1. Include all items on your list.

Introduce Goal 1. Define λmax and give expected outcomes.

Plan of action. How was Goal 1 achieved? Introduce techniques/formulas/chemicals in context.

Relevance of results. What can you do with your newly found λmax?

GenChem

Introduction: Goal 1

*

Introduction: Goal 2

In a paragraph, introduce Goal 2. Include all items on your list.

Introduce Goal 2. Define ε and give expected outcomes.

Plan of action. How was Goal 2 achieved? Introduce techniques/formulas/chemicals in context.

Relevance of results. What can you do with your newly found ε?

GenChem

Introduction: Goal 2

Goal 2 was to find ε for the assigned dye. ε is a measure of how strongly a substance absorbs light at a particular wavelength and is a large value for dark colorful substances. In Beer’s Law, ε is the proportionality constant that relates absorbance to concentration (A=εbC).

To determine ε, Absorption Spectroscopy was used to measure absorbance values (at the λmax) of several dilutions of dye with known concentrations. An Excel graph of A vs. C was generated so slope=εb. The slope was given by the Excel trend line and the path length (b) of the cuvette was measured with calipers. ε can be used to determine the concentration of food dye in unknown solutions.

GenChem

Introduction

The first goal was to determine the λmax of the assigned food dye. The λmax of a substance is the wavelength of light with the highest absorbance and is the wavelength opposite the color seen by the human eye. The λmax was determined using Absorption Spectroscopy, a technique that measures the wavelengths of light absorbed by a colored solution. The λmax was then used to conduct a Beer’s Law analysis in Goal 2.

Goal 2 was to find ε for the assigned dye. ε is a measure of how strongly a substance absorbs light at a particular wavelength and is a large value for dark colorful substances. In Beer’s Law, ε is the proportionality constant that relates absorbance to concentration (A=εbC).

To determine ε, Absorption Spectroscopy was used to measure absorbance values (at the λmax) of several dilutions of dye with known concentrations. An Excel graph of A vs. C was generated so slope=εb. The slope was given by the Excel trend line and the path length (b) of the cuvette was measured with calipers. ε can be used to determine the concentration of food dye in unknown solutions.

GenChem

Introduction: Helpful hints

Only include information that is known before lab. No results, observations, etc.

200 word maximum for one week lab.

Paragraph format. Subheadings okay.

Give items in context. No lists.

See Technique Book pp. 65, 67 and 71 for more help with writing an Introduction

See Technique Book pp. 52-55 for more help with scientific writing.

GenChem

Procedures

Also known as “experimental”. This section will be discussed with the next report.

GenChem

Calculations

Calculations. Examples of all calculations performed to manipulate the numerical data. Include one example for each type.

From p. 70 of your Technique Book:

One example for each type of calculation. Each example should consist of three parts:

The formula that describes the calculation

The formula in use

Question to ask yourself:

For each goal identify the important calculations that should be included.

Determine λmax

Determine at λmax.

Calculation of a value for .

GenChem

Calculations

Your presentation of your calculations should always use a three step format:

Write out the equation

Plug in your numbers

Give the answer

This method ensures that your instructor can follow your thought process during the calculation.

Do not forget to add units and watch significant figures during your calculations!

GenChem

Calculations: Goal 1

For a dilution the product of the concentration times the volume is constant.

C1V1 = C2V2

C2 = 5.37 x 10-5 M

*

Calculations: Goal 2

The first calculation of goal 2 is the same as that of goal 1: dilution. Since we have already shown this calculation, we do not need to show it again.

If we calculated the concentration a different way, then we would need to show a second calculation.

GenChem

Calculations: Goal 2

The second calculation we have listed is density. We obtained this value from the graph, but it would be helpful to make a note in the calculations so that the reader does not think you forgot one:

Density of known plastic: Determined from the slope of the graph

GenChem

Calculations: Helpful Hints

Include a calculation for all types of calculations that you do, but only include one example for the type of calculation

Watch significant figures and units

GenChem

Results

From p. 65 of your Technique Book:

Results. An organized presentation of the observations and calculated results. This section is frequently dominated by figures, tables and graphs. It will contain little to no text.

From pp. 67-8 of your Technique Book:

Results. An objective and clear description of experimental findings following an appropriate order and including relevant:

Tables

Graphs

Figures

GenChem

Question to ask yourself:

For each goal identify the important results and supporting data that should be included.

Determine λmax

Calculation of a value for .

GenChem

Results: Goal 1

Sometimes, it makes more sense to list numbers and answers in a clear order rather than putting them in a table.

Dye: Indigo carmine

λmax : 610 nm

Figure 1: Visible-UV spectrum of indigo carmine

GenChem

Results: Goal 2

For repetitive and/or related data a labeled table is best. Compile all of the items on your list in a logical order.

Table 1. absorbance of standard solutions

* Ratio of stock solution volume to final solution volume

** absorbance values measured at 610 nm

Dilution*

Results: Goal 2

It is often a good idea to display this information in a graph as well. If we plot the absorbance on the x-axis and the concentration on the y-axis, the slope will be the molar absorptivity of the dye.

Graph 1. absorbance vs concentration of standard food dye solutions.

at 610 nm = 5.50 x 105 abs/cmM

*

Results: Helpful Hints

Only include results that are important to the conclusions that you make

Be careful about the amount of significant figures you have, especially when copying tables that you’ve made from Excel

GenChem

Discussion

From your Technique Book:

Discussion. Analysis of the data and presentation of conclusions regarding original hypothesis. This should include a defense of the conclusions citing the results and a discussion of the reliability of the data used.

GenChem

What does it mean?

Does it make sense?

Is it consistent with your observations?

Comparisons to literature or peers.

If something went wrong: What were you expecting and why? What went wrong? How do you know? How could you fix it next time?

GenChem

Discussion: Goals

The λmax of Blue #1 was 610 nm which lies in the orange region of the visible light spectrum. As expected, the orange color absorbed is opposite the blue color observed.

Using the λmax, the ε for Blue #1 was found to be 55,000 M-1cm-1. This is a larger ε than the other three dyes, which means Blue #1 is the best at absorbing light. This is consistent with the observation that Blue #1 had the darkest appearance out of the four dyes.

GenChem

Discussion: Data quality

In a paragraph, discuss the quality and reliability of your data:

Discuss pros/cons/accuracy/precision of tools/techniques.

Be specific and give examples.

Suggest fixes for the problems you identify and additional experiments to improve findings.

Avoid discussing general human error. Only specific, documented errors should be addressed.

GenChem

Discussion: Data quality

The λmax value seems reliable because the spectrometer gives readings that vary by a maximum of 1 nm. Also, 610 nm is an exact match to the class average λmax. The ε value also came close to the class average ε of 55,000 M-1cm-1. The calipers used to measure the path length are accurate to 0.01 cm and the volumetric kit used for dilutions measures volumes accurate to 0.01 mL.

*

GenChem

Discussion