Lab Report Format

GENERAL GUIDELINES FOR WRITING LAB REPORTS

Always write in the third person passive voice. Say "If the lab were to be repeated," rather than "If I were to do the lab again."
Write in a professional manner. Be complete and detailed, but also concise.
Your work must be your own. Do not copy or even re-word someone else's work.

The lab report has five main sections:

Abstract
Observations
Data Table and Graphs
Sample Calculations
Error Analysis
Details about each section are provided below.

FORMAT

Name:
Title of Lab
Partner
Date

1. Abstract

The abstract is a two-three paragraph summary of your entire report. The purpose of an abstract is to allow the reader to quickly understand your work. Many readers only read the abstracts, so it is important to include all of the relevant information, but in a concise form.

The first paragraph of the abstract should include:

The purpose of the experiment (Good purpose:“..to measure the heat capacity of copper and aluminum and compare them to the accepted values.” Bad Purpose: "..to learn about heat." ). Do not start your abstract with "The purpose of the experiment was..." Instead just get right into what was measured.
A brief summary of the procedure
Your results, including comments on accuracy and precision.
A final sentence commenting on the quality of this work

The second paragraph should include

List at least three things that could be changed to make the procedure more accurate or precise. Explain why each change should be made.
- Example of a good suggestion: “If the lab were to be a repeated, the sample could be reheated a third time. This would drive any remaining water from the sample.”
- Examples of poor suggestions:
  - "The instructions should have provided more detail."
  - "I should time things more closely because I let one trial heat too long."
  - "I should do more trials."

The third paragraph should answer any Additional Questions that are provided with some labs. You may also use this final paragraph to add any additional explanations pertinent to the lab.

A sample abstract for a simple density experiment might read:

"The density of a sample of aluminum was determined and compared to the literature value of 2.70 g/mL. The volume was measured using water displacement in a graduated cylinder, and the mass was measured on an electronic balance. The density was calculated using the formula: density=mass/volume. The average experimental density of 2.65 g/mL agreed with the literature value with a percent error of 1.9%. The four trials had a precision of 0.13 g/mL. These results indicate that this is an effective method for determining the density of a solid sample of metal.

If the lab were to be repeated, students should carefully slide the metal pieces down the side of the graduated cylinder. This would prevent any splashing that would lower the recorded volume of the sample. A second way to improve the accuracy would be to first melt the zinc pieces into a smooth sample. The zinc pieces had a number of holes and pits which could have trapped air bubbles. This would increase the recorded volume of the sample. A third way to improve the experiment would be to dry the metal pieces between trials with a hair dryer to drive off any excess water."

2. Observations (A short paragraph)

Example- "When copper and sulfur were heated, a blue flame was seen at the top of the crucible. Towards the end of the heating, the flame disappeared."
Write the chemical reaction that occurred as part of this paragraph.

3. Data Tables and Graphs

Sample Data Table


trial	1	2	3	4

P(atm)	0.2	0.5	0.7	1.0
T(^oC)	50	50	100	100
yield (%)	25	60	80	85
average yield (%)	63

Sample Graph

4. Sample Calculations (only show one trial)

This section should allow the reader to follow every step of your calculations clearly. You should label each step with a short sentence or phrase. One possible format is:

Calculating density

	Calculating the total volume (Final volume - Initial volume):	37.2 mL - 26.4 mL = 10.8 mL
	Calculating the mass (Total mass - Mass of Dish):	54.96 - 25.80 g = 29.16 g
	Calculating the Density (D=M/V):	29.16 g/10.8 mL = 2.70 g/mL

5. Error Analysis (Show the calculation)

Accuracy

% Error = |(Experimental - Accepted)/Accepted| X 100

Note that the Percent Error is always a positive number.

Precision

The precision should always refer to one (and only one) measurement in the lab. It should be the item you said you were going to measure in the first sentence of your abstract. For example, in the sample abstract given, your range would be the range of the densities of aluminum measured in the trials.

Range = Highest Value - Lowest Value

Remember to always compare the size of your range to the size of the numbers being measured. For example, 1.5 is a small range if you are measuring the boiling point of water, 100^oC. However, 1.5 is a large value if you are measuring an acceleration of 3.3 m/s².

APPENDIX: KEEPING A PROPER LAB NOTEBOOK

On the Cover

Your name
A.P. Chemistry
Room 20, Mr. Fredericks

Centered on the First Page

Your name
A.P. Chemistry
Room 20, Mr. Fredericks
August 2009 to May 2010

On the Second Page

Table of Contents
List the name of all of the labs and the page numbers in your notebook (number your pages when you get time.)

General Rules

You must sign and date the top of the page whenever you start a new lab. Use the first line and the upper right hand corner. If you are continuing from a previous day, sign and date the first line where you right new information.
All writing must be in PEN. Pencils are not allowed in formal lab notebooks.
No recopying. All information is taken in the lab book. Do not take information on scrap paper and transfer it later.
Both partners are responsible for copying all information. No excuses.
Use a single line ~~cross-out~~. Do not scribble or color in bad information. You must be able to read even crossed-out information.