In chemistry experiments, not only the report submitted after the experiment but also the “laboratory notebook” used to record information during the experiment is very important. If the laboratory notebook is incomplete, it may become difficult to determine measured values, observations, the order of procedures, causes of failure, and other details when writing the report later.
This article clearly organizes the items that should be recorded in a chemistry laboratory notebook, how to write during an experiment, and how to use the notebook when preparing a report. Use it as a reference for students writing reports for university basic chemistry experiments, organic chemistry experiments, analytical chemistry experiments, and similar laboratory courses.
Note: The format and submission method for laboratory notebooks may differ depending on the university, course, or instructor. The content of this article is a general reference example. In actual classes, give priority to the laboratory manual provided and the instructions of your instructor.
- What Is a Laboratory Notebook?
- Difference Between a Laboratory Notebook and a Laboratory Report
- What to Write Before the Experiment
- Items to Record During the Experiment
- Basic Principles for Writing a Laboratory Notebook
- Information That Is Useful in a Report When Recorded in a Laboratory Notebook
- Example of a Laboratory Notebook That Is Easy to Use in a Report
- Common Examples of Poor Laboratory Notebook Entries
- How to Write a Discussion from a Laboratory Notebook
- Process for Converting a Laboratory Notebook into a Report
- Common Mistakes in Laboratory Notebooks
- Example Expressions That Are Easy to Use in Reports
- Checklist for Writing a Laboratory Notebook
- Summary
What Is a Laboratory Notebook?
A laboratory notebook is a notebook in which you record the procedures performed during an experiment, observed changes, measured values, things you noticed, and other information at the time they occur. It is not a draft for writing a report, but a primary record for accurately documenting the experiment.
In chemistry experiments, even when you believe you are following the same procedure, the results may change depending on the amount of reagent, temperature, time, order of mixing, filtration conditions, drying conditions, and other factors. Therefore, recording what occurred during the experiment is useful for later discussion.
A laboratory notebook is used for purposes such as the following.
- To review experimental procedures later
- To preserve measured values and observations accurately
- To provide material for writing the results and discussion sections of a report
- To consider why an experiment did not go well
- To provide a reference when repeating an experiment or changing conditions
Particularly in university chemistry experiments, the content of the laboratory notebook directly affects the quality of the report. This is because information that was not recorded during the experiment can be difficult to remember accurately later.
Difference Between a Laboratory Notebook and a Laboratory Report
A laboratory notebook and a laboratory report may seem similar, but their roles are different. A laboratory notebook is a “record made during the experiment,” while a report is “a written document in which experimental results are organized and discussed.”
| Item | Laboratory Notebook | Laboratory Report |
|---|---|---|
| Purpose | Record facts during the experiment | Organize and discuss the results |
| When to write | Before, during, and immediately after the experiment | After the experiment |
| Content | Procedures, measured values, observations, things noticed | Purpose, principles, methods, results, discussion, conclusion |
| Writing style | Record specific details on the spot | Organize the information so that it is understandable to the reader |
A laboratory notebook does not need to be written in polished prose. However, it is important to clearly record numerical values, units, times, and observations so that the meaning can be understood when the notebook is read later.
What to Write Before the Experiment
A laboratory notebook is not something that should only be started after the experiment begins. Organizing the necessary information beforehand makes it easier to record information during the experiment without becoming rushed.
Items to Record Before the Experiment
- Date of experiment
- Experiment title
- Names of laboratory partners
- Purpose of the experiment
- Principles of the experiment
- Reagents to be used
- Equipment to be used
- Reagent concentrations and molecular weights
- Necessary calculations
- Hazards and safety precautions that require attention
In particular, reagent concentration, molecular weight, density, amount used, and similar values will be needed for calculations after the experiment. Checking them again during the experiment takes time, so it is useful to organize them in advance.
Example of a Pre-Experiment Record:
Experiment title: Determination of Acetic Acid Concentration by Acid–Base Titration
Purpose: To determine the concentration of acetic acid in vinegar using a standard sodium hydroxide solution.
Values to record: Concentration of the sodium hydroxide solution, dilution factor of the vinegar, volume of sample used, and type of indicator.
Items to Record During the Experiment
During the experiment, record information that may be related to the results as much as possible at the time it occurs. If you plan to write everything down later, you may forget small changes and differences in procedures.
Measured Values
Measured values should be recorded together with units and significant figures. Mass, volume, temperature, pH, time, absorbance, titration volume, and similar values are directly related to the experimental results and discussion.
- Mass: g, mg
- Volume: mL, L
- Temperature: °C, K
- Time: s, min
- Concentration: mol/L, g/L
- pH
- Absorbance
- Titration volume
If you record only a number and forget the unit, it may become impossible to use the value in later calculations. For example, instead of writing only “12.4,” record it as “12.40 mL.”
Observations
In chemistry experiments, observations are important in addition to numerical values. Changes in color, formation of precipitates, gas evolution, heat generation, odor, crystal shape, and similar observations provide clues for determining whether a reaction proceeded.
- The color of the solution changed
- A precipitate formed
- Bubbles were produced
- The temperature increased
- Crystals precipitated
- The solution became cloudy
- The mixture separated into two layers
- An emulsion formed
Observations should be written as specifically as possible rather than using only descriptions such as “beautiful,” “a lot,” or “a little.” For example, writing “the colorless, transparent solution changed to pale yellow” is more useful for the report than simply writing “it turned yellow.”
Changes in Procedure and Mistakes
If the experiment did not proceed as planned, record that information as well. Rather than hiding mistakes, recording what happened allows the information to be used in the discussion.
- The order of adding reagents was incorrect
- The heating time became longer than planned
- Part of the sample was lost during filtration
- The endpoint was exceeded during titration
- The crystals were insufficiently dried
- Temperature control was insufficient
Such information may be used in the discussion section of the report as a “cause of low yield” or a “cause of large error.”
Basic Principles for Writing a Laboratory Notebook
A laboratory notebook should be written so that the sequence of the experiment can be understood when it is reviewed later. It does not need to be perfect prose, but at minimum, the record should be understandable to anyone who reads it.
Write Information on the Spot
A laboratory notebook should not be written all at once after the experiment is finished; information should be recorded during the experiment as it occurs. In particular, titration volumes, temperatures, color changes, formation of precipitates, and similar details can be difficult to remember accurately after time has passed.
Write in Chronological Order
Procedures and observations should be recorded in the order in which the experiment proceeds. Writing chronologically makes it easier to confirm later “after which operation a particular change occurred.”
Include Units with Numerical Values
Always include units with measured values. A numerical value without a unit may become meaningless when viewed later.
Leave Corrections Legible
In a laboratory notebook, rather than completely erasing incorrect information, it is preferable to leave the original entry legible. For example, cross it out with a double line and write the correct value.
Example of a Correction:
Titration volume: 12.10 mL 12.40 mL
Reason: The burette graduation was reread.
Correction fluid and erasable pens may be prohibited in some classes because they make the original record impossible to identify.
Information That Is Useful in a Report When Recorded in a Laboratory Notebook
A laboratory notebook provides material for writing a report. Recording the following types of information is useful when writing the results and discussion.
| Information Recorded | Where It Can Be Used in the Report |
|---|---|
| Measured values | Results, calculations, graphs |
| Color changes | Reaction progress, discussion of qualitative analysis |
| Presence or absence of precipitate | Confirmation of reaction, discussion of causes of error |
| Titration volume | Concentration calculation, discussion of endpoint determination |
| Heating time and temperature | Discussion of reaction progress, decomposition, and side reactions |
| Conditions during filtration, washing, and drying | Discussion of reduced yield and reduced purity |
| Mistakes and operational errors | Causes of error, improvements |
Even information that does not seem important during the experiment may become necessary when writing the report. Detailed laboratory notebook records are particularly useful when considering questions such as “Why did the result differ from the theoretical value?” or “Why was the yield low?”
Example of a Laboratory Notebook That Is Easy to Use in a Report
It is convenient to write a laboratory notebook in a form that can easily be converted into a report later. The following is an example of a record for a titration experiment.
Example of a Laboratory Notebook Entry:
10:15 Collected 10.00 mL of vinegar using a volumetric pipette and diluted it to 100 mL in a volumetric flask.
10:25 Placed 10.00 mL of the diluted sample in a conical flask and added two drops of phenolphthalein.
10:30 Started titration with 0.100 mol/L NaOH solution.
1st measurement: Slightly exceeded the endpoint, and the solution became dark red. Titration volume: 8.95 mL.
2nd measurement: Pale red color remained for approximately 30 seconds. Titration volume: 8.72 mL.
3rd measurement: Pale red color remained for approximately 30 seconds. Titration volume: 8.70 mL.
If the information is recorded in this way, it can be used in the report as follows.
Example of Use in a Report:
In the first titration, the endpoint was exceeded and the solution became dark red, so the titration volume may have been larger than the actual value. Therefore, the average titration volume was calculated mainly using the values from the second and third titrations. The titration volumes from the second and third measurements were close to each other, suggesting that endpoint determination had relatively good reproducibility.
By recording observations such as “the endpoint was exceeded” or “the color became darker” in the laboratory notebook, these details can be explained specifically in the discussion.
Common Examples of Poor Laboratory Notebook Entries
If a laboratory notebook is incomplete, it becomes difficult to write the report. The following types of entries should be avoided.
Writing Only Numerical Values
8.95, 8.72, 8.70
With this type of entry, it is impossible to determine what the values represent, what the units are, or which measurement each value corresponds to.
Titration volume: 1st measurement 8.95 mL, 2nd measurement 8.72 mL, 3rd measurement 8.70 mL
Vague Observations
The color changed.
Because this does not indicate which color changed into which other color, it is difficult to use in the report.
The colorless, transparent solution changed to pale red near the titration endpoint, and the color remained for approximately 30 seconds.
Not Recording Mistakes
If a mistake occurred during the experiment and it is not recorded, it becomes impossible to explain the cause of error in the report. Rather than hiding a mistake as something bad, record it as a fact that may have affected the results.
How to Write a Discussion from a Laboratory Notebook
A laboratory notebook provides the material used to write the discussion. When writing the discussion, consider “how the result was affected” based on the facts recorded in the notebook.
Examples of Records That Can Be Used in the Discussion
| Laboratory Notebook Entry | What Can Be Written in the Discussion |
|---|---|
| Part of the crystals remained on the filter paper during filtration | The recovered amount may have decreased, resulting in a lower yield |
| Drying time was short | Moisture may have remained in the sample, causing the measured mass to be larger than the actual value |
| The endpoint was exceeded during titration | The titration volume may have been overestimated, causing an error in the concentration calculation |
| The heating temperature became too high | Side reactions or decomposition may have occurred, affecting yield or purity |
| The pH meter value did not stabilize | Insufficient electrode cleaning or temperature changes may have caused variation in the measured values |
In the discussion, simply writing that “the value differed because the experiment failed” is insufficient. Explaining “which operation,” “which measured value,” and “in which direction” the result was affected makes the discussion more convincing.
Process for Converting a Laboratory Notebook into a Report
A laboratory notebook is rarely submitted directly as a report, but by organizing the notebook contents, they can be converted into the various sections of the report.
- Extract measured values from the laboratory notebook
- Organize them into tables
- Perform the necessary calculations
- Create graphs
- Write the observations in sentences
- Compare the results with theoretical or literature values
- Consider causes of error
- Write improvements
When writing a report, first dividing the information in the notebook into “results” and “discussion” makes it easier to organize.
| Notebook Content | Classification in the Report |
|---|---|
| Measured values, mass, volume, pH, titration volume | Results |
| Average values, yield, concentration calculations | Results / Calculations |
| Color changes, precipitates, crystal shape | Results / Observations |
| Operational mistakes, temperature changes, insufficient drying | Discussion / Causes of error |
| Points to improve next time | Discussion / Improvements |
Common Mistakes in Laboratory Notebooks
Knowing common mistakes in laboratory notebooks can help prevent problems when preparing the report.
Forgetting to Write Units
If only numerical values are recorded and units are omitted, the values may become unusable in later calculations. Always include units for mass, volume, temperature, time, concentration, and similar measurements.
Ignoring Significant Figures
Record values with attention to significant figures according to the precision of the instrument used in the experiment. For example, a value read from a burette and a value measured approximately do not have the same number of reliable digits.
Not Recording Observations
Record not only measured values but also color, precipitates, bubbles, heat generation, the appearance of crystals, and similar observations. Observations provide information for determining whether the experiment proceeded correctly.
Not Recording Mistakes or Abnormal Events
If something different from what was planned occurs, record it. This information is useful when writing causes of error and improvements.
Planning to Write Everything Later
If you plan to write everything after the experiment, you may forget small changes or exact measured values. The basic rule is to write the laboratory notebook on the spot during the experiment.
Example Expressions That Are Easy to Use in Reports
Information recorded in a laboratory notebook should be rewritten into objective sentences when used in a report. The following are examples of converting laboratory notebook entries into report-style expressions.
| Laboratory Notebook Entry | Example Expression for a Report |
|---|---|
| It turned a little red | The solution changed from colorless to pale red. |
| Spilled a little during filtration | Because part of the sample was lost during filtration, the recovered amount may have decreased. |
| Maybe it was not dry enough | If drying was insufficient, moisture may have remained in the sample, causing the measured mass to be larger than the actual value. |
| The temperature became too high | The high heating temperature may have caused side reactions or decomposition to proceed. |
| The values varied | Possible causes of the variation in measured values include individual differences in endpoint determination and errors in reading the instrument. |
In a report, it is important to avoid conversational expressions and use objective, specific wording.
Checklist for Writing a Laboratory Notebook
If you are unsure what to write during an experiment, checking the following items can be useful.
- Did you write the date and title of the experiment?
- Did you briefly organize the purpose and principles?
- Did you record the concentrations and amounts of the reagents used?
- Did you include units with measured values?
- Did you record temperature and time?
- Did you record observations such as color changes and precipitate formation?
- Did you record operational mistakes and unexpected events?
- Did you preserve the values needed for calculations?
- Will the meaning be understandable when you review it later?
- Did you record information that may be useful in the discussion section of the report?
Summary
A chemistry laboratory notebook is not merely a collection of notes but an important record for accurately preserving experimental results and writing the results and discussion sections of a report. Specifically recording measured values, observations, changes in procedures, mistakes, and abnormal events during the experiment can greatly improve the quality of the report.
Detailed records in the laboratory notebook are particularly useful when writing the discussion. Even when the yield is low, measured values vary, or results differ from theoretical values, the causes can be explained specifically if the conditions during the experiment were recorded in the notebook.
When writing a laboratory notebook, focus on recording information “on the spot,” “specifically,” “with units,” and “in a way that can be understood later,” rather than trying to write polished prose.
