In university basic chemistry experiments, not only the experiment itself but also the report submitted afterward is important. In particular, many students struggle because they do not understand the difference between “results” and “discussion” or what they should write in each section.
This article clearly organizes the basic structure of a basic chemistry laboratory report, how to summarize results, how to write the discussion, and how to think about causes of error. Because experimental data differ depending on the university and experimental conditions, use the content introduced here as a reference and adapt it to your own measured values and observations rather than copying it directly.
Note: This article is a reference for students who have performed experiments in university or similar classes to understand how to approach laboratory report writing. For experimental procedures and safety management, always follow your university’s laboratory manual and the instructions of your instructor or teaching assistant (TA).
- Important Points in a Basic Chemistry Laboratory Report
- Basic Structure of a Laboratory Report
- Difference Between “Results” and “Discussion”
- How to Write the Results
- How to Write Calculation Results
- How to Create and Interpret Graphs
- How to Write the Discussion
- How to Think About Causes of Error
- Common Discussion Points for Different Experiments
- Useful Expressions for the Discussion
- Discussions That Should Be Avoided
- How to Write the Conclusion
- Checklist for Writing a Basic Chemistry Laboratory Report
- Summary
Important Points in a Basic Chemistry Laboratory Report
What is important in a basic chemistry laboratory report is not simply writing “the experiment was performed” and “these were the results.” Based on the data obtained from the experiment, it is necessary to explain why the result occurred, how it compared with theoretical values or expectations, and, if there was an error, what may have caused it.
In university laboratory reports in particular, the following three points are emphasized.
- Whether the experimental results are organized accurately
- Whether the results are discussed scientifically
- Whether the causes of errors and failures are explained specifically
Simply writing “it did not go well” or “I think the experiment failed” is insufficient as a discussion. It is important to explain specifically what affected the result and how.
Basic Structure of a Laboratory Report
A basic chemistry laboratory report is generally written using the following structure. If your university or course specifies a particular format, always give priority to that format.
- Title
- Purpose
- Principle
- Equipment and Reagents
- Experimental Procedure
- Results
- Calculations
- Discussion
- Conclusion
- References
Among these sections, students often have the most difficulty with “Results” and “Discussion.” The Results section presents facts obtained from the experiment, while the Discussion section explains the meaning of those results.
Difference Between “Results” and “Discussion”
In a laboratory report, it is important not to confuse the Results and Discussion sections. The Results section contains facts obtained from the experiment, such as measured values, observations, calculated results, and graphs. In contrast, the Discussion section explains what those results mean, whether they agree with theory, and what caused any errors.
| Section | What to Write | Examples |
|---|---|---|
| Results | Facts obtained from the experiment | Measured values, color changes, presence or absence of precipitate, yield, pH, graphs |
| Discussion | What can be inferred from the results | Causes of error, differences from theoretical values, progress of the reaction, improvements |
For example, in a recrystallization experiment, writing “1.20 g of crystals was obtained” belongs in the Results section. Writing “One possible cause of the low yield is that some crystals adhered to the filter paper or equipment during filtration” belongs in the Discussion section.
How to Write the Results
When writing the Results section, organize the data obtained from the experiment clearly. Using tables and graphs in addition to text can make the results easier to read.
What to Include in the Results
- Measured values
- Observations
- Calculated results
- Amount obtained and yield
- Measured values such as pH and temperature
- Values read from graphs
- Changes such as color changes, precipitation, and gas evolution
Results should be written as objectively as possible. Writing only “beautiful crystals formed” is subjective, so it is better to describe the observed facts, such as “white needle-like crystals were obtained” or “coloration was observed in part of the crystals.”
Example of Writing the Results
After recrystallization, white crystals were obtained. The mass of the crystals after drying was 1.20 g. Assuming a theoretical yield of 1.80 g, the yield was 66.7%. In addition, the melting point of the obtained crystals was 132–134°C, which was slightly lower than the literature value, and the melting point range was also broader.
In this way, the Results section should focus on “what was obtained” and “what values were obtained.” The meaning and causes of the results are discussed in detail in the following Discussion section.
How to Write Calculation Results
In chemistry laboratory reports, measured values are often used to calculate concentration, amount of substance, yield, error percentage, and other quantities. Do not omit too much of the calculation process; write it so that it is clear which values were used.
Example of Yield Calculation
Yield indicates how much was actually obtained relative to the theoretical maximum amount.
Yield (%) = Actual amount obtained ÷ Theoretical yield × 100
For example, if the theoretical yield is 1.80 g and the actual amount of crystals obtained is 1.20 g, the yield is calculated as follows.
Yield = 1.20 ÷ 1.80 × 100 = 66.7%
Possible reasons why the yield is below 100% include incomplete reaction, loss of sample during filtration or transfer, and part of the desired substance remaining in the mother liquor during recrystallization.
Example of Error Percentage Calculation
When comparing an experimental value with a theoretical or literature value, an error percentage may be calculated.
Error (%) = |Experimental value − Theoretical value| ÷ Theoretical value × 100
After calculating the error percentage, it is important not to stop with the numerical value but to discuss what caused the error.
How to Create and Interpret Graphs
Graphs may be created in experiments involving titration, spectrophotometry, reaction rates, temperature changes, and similar measurements. A graph is not merely decorative; it is an important resource for visually presenting experimental results and identifying trends or anomalous values.
Elements Required in a Graph
- Graph title
- Labels for the horizontal and vertical axes
- Units
- Measurement points
- Regression line or fitted curve
- Correlation coefficient or equation when necessary
For example, when creating a calibration curve in spectrophotometry, concentration is plotted on the horizontal axis and absorbance on the vertical axis. If absorbance increases linearly as concentration increases, the measurement range can be considered to approximately follow the Beer–Lambert law.
Discussion Example for a Graph
In the calibration curve, absorbance increased as concentration increased, and an approximately linear relationship was observed within the measurement range. This indicates that the relationship in which absorbance is proportional to concentration was generally followed. On the other hand, possible reasons why measurement points at higher concentrations deviated slightly from the regression line include an excessively high sample concentration, contamination of the cell, bubbles during measurement, and deviation in zero adjustment.
How to Write the Discussion
In the Discussion section, explain “why the result occurred” based on the results. It is one of the most important sections of a laboratory report.
When writing the discussion, following the sequence below can make it easier to organize.
- Briefly confirm the obtained result
- Compare it with theoretical values, literature values, or expectations
- Organize the points that agreed and the points that differed
- Consider the causes of differences and errors
- Write improvements and points to be careful about next time
In the discussion, simply writing “I was bad at the experiment” or “I made a mistake” is insufficient. Explain specifically which operation or condition affected the result and how.
Example of a Superficial Discussion
The yield was low. This is considered to be because the experiment failed. I want to be more careful next time.
Example of an Improved Discussion
The yield of the obtained crystals was 66.7%, which was lower than the theoretical value. Possible reasons for the reduced yield include some of the desired substance remaining dissolved in the mother liquor during recrystallization and some crystals adhering to the filter paper or equipment during suction filtration. In addition, if too much washing solution was used when washing the crystals, part of the desired substance may have dissolved, reducing the amount recovered.
The improved example lists multiple specific causes for the low yield. Relating the discussion to experimental procedures and chemical properties in this way makes it more appropriate as a scientific discussion.
How to Think About Causes of Error
Experimental values rarely agree perfectly with theoretical or literature values. Therefore, considering possible causes of error is important in a laboratory report.
However, when writing causes of error, avoid explaining everything simply as “human error.” Errors may arise from procedures, instruments, reactions or sample properties, and environmental conditions.
| Type of Error | Examples | Example of How to Write It in the Discussion |
|---|---|---|
| Operational error | Transfer, filtration, washing, reading | Part of the sample may have been lost during the procedure. |
| Instrument error | Burette, pipette, balance, pH meter | The reading accuracy or calibration condition of the instrument may have affected the result. |
| Reaction-related error | Incomplete reaction, side reaction, decomposition | The amount of product may have decreased because the reaction did not proceed to completion. |
| Sample-related error | Impurities, moisture absorption, insufficient drying | The sample may have contained moisture or impurities. |
| Environmental error | Temperature changes, carbon dioxide in the air, humidity | Temperature changes during measurement may have affected the measured value. |
Common Discussion Points for Different Experiments
In basic chemistry experiments, the points that should be discussed differ depending on the experimental topic. This section briefly organizes the direction of discussion for commonly performed experiments.
Recrystallization
In recrystallization, the relationship between yield and purity is important. When attempting to increase purity, part of the desired substance may remain in the solvent, causing the yield to decrease. If the melting point is close to the literature value and the melting point range is narrow, the purity can be considered relatively high.
Melting Point Measurement
In melting point measurement, not only the melting point value but also the range from the beginning to the end of melting is important. If impurities are present, the melting point may decrease or the melting point range may broaden.
Filtration
In filtration, how much of the precipitate or crystals could be recovered is important. If the recovery is low, possible causes include adhesion to filter paper, loss during washing, and fine precipitate particles passing through the filter paper.
Distillation
In distillation, the boiling point, distillation temperature, and amount of each fraction are used to discuss how effectively the mixture was separated. If the temperature does not remain constant or components other than the desired component are present, the heating rate, tightness of the apparatus, and fractionation efficiency should be examined.
pH Measurement
In pH measurement, calibration of the pH meter, cleaning of the electrode, temperature, and sample uniformity affect the result. If the measured value differs from the expected value, it is useful to consider whether calibration with standard solutions was appropriate and whether the previous sample remained on the electrode.
Volume Measurement
In experiments using volumetric flasks, volumetric pipettes, and burettes, possible sources of error include meniscus reading, bubbles, insufficient rinsing of the instrument with the solution, and dripping. Particularly in titration, adding solution beyond the endpoint may cause a large error in the concentration being determined.
Useful Expressions for the Discussion
In the Discussion section, it is important not to make overly definitive statements and to use expressions that remain within what can reasonably be inferred from the experimental results. The following expressions can make the writing more appropriate for a laboratory report.
- From this result, it is considered that ~.
- Compared with the theoretical value, the experimental value was slightly higher.
- One possible reason for this difference is ~.
- One factor that may have contributed to the reduced yield is ~.
- The broad melting point range suggests the presence of impurities.
- One possible cause of the variation observed in the measured values is ~.
- As an improvement for future experiments, ~ should be performed more accurately.
However, rather than simply using these expressions as they are, it is important to make the content specific to your own experimental results.
Discussions That Should Be Avoided
In laboratory reports, the following types of discussion should be avoided.
- Writing only “because the experiment failed”
- Writing only “human error”
- Simply repeating the results
- Making unsupported definitive statements
- Writing only general information unrelated to the experimental results
- Copying explanations directly from the laboratory manual or textbook
For example, simply writing “the yield was low because of human error” does not explain the actual cause. It is necessary to connect a specific operation with the result, such as “some crystals may have remained on the filter paper or equipment during suction filtration.”
How to Write the Conclusion
In the Conclusion section, briefly summarize what was confirmed through the experiment as a whole. It is not necessary to repeat everything stated in the Discussion section.
Example of a Conclusion
In this experiment, the crude product was purified by recrystallization, and white crystals were obtained. The yield was 66.7%, which was lower than the theoretical yield, but melting point measurement confirmed that the purity improved to some extent through recrystallization. The main causes of the reduced yield are considered to be dissolution losses in the mother liquor and adhesion losses during filtration.
A conclusion is easier to organize when it directly answers the purpose of the experiment.
Checklist for Writing a Basic Chemistry Laboratory Report
After finishing the report, check the following points before submitting it.
- Is the purpose of the experiment clearly stated?
- Are the Results and Discussion sections kept separate?
- Are units included with measured values?
- Are significant figures consistent?
- Are the equations and calculation steps written clearly enough to follow?
- Are axis labels and units included on graphs?
- Are causes of error described specifically?
- Is the discussion based on your own experimental results?
- Are references cited appropriately?
- Is the explanation written in your own words rather than copied directly?
Summary
In a basic chemistry laboratory report, it is important to accurately organize the experimental results and explain what can be inferred from them. In particular, it is important to separate the Results and Discussion sections, consider causes of error specifically, and compare the experimental results with theoretical or literature values.
To write a good discussion, rather than simply writing that “the experiment failed” or “there was an error,” it is necessary to consider specifically which operation or condition affected the result. Use your own measured values, observations, graphs, and calculation results to explain the meaning of the experiment.
Basic chemistry experiments provide the foundation for progressing to more specialized chemistry experiments. Through laboratory report writing, it is important to develop the ability to organize data, interpret results, and discuss them scientifically.
