Lab Reports

Everything You Didn’t Want to Know!

Components of a Lab Report

Title Purpose Procedure Safety Data Calculations Conclusion

How to Write a Lab Report

Title:

• Placed at top center of page one

• Descriptive and appropriate

Purpose:

• One sentence telling why the lab was performed

Procedure:

• A paragraph summarizing how the lab was performed.

• Include key concept(s), formula, and/or

chemical equation

Safety:

• Specify safety rules by contract #

Density of Solids

Purpose: TPOTLIT investigate the density of various solids.

Procedure: The relationship between the mass of an object and its volume is called density. The mass and volume of various cubed shaped substances were determined. The density was calculated by dividing the mass of the cube by its volume.

Safety: #1,4,5,7 & 8

Includes both qualitative and quantitative observations

Quantitative data should be arranged in a data table format

Always use units of measurements

Always use Significant Figures

Data:

Cylinder Mass (g) Volume (ml) Density (g/ml)

aluminum 5.40 1.8 3.0 copper 18.00 2.0 9.0brass 15.60 2.0 7.8lead 22.80 2.0 11.4iron 15.80 2.0 7.9

Data

Calculations * Show a sample of

how the calculation was performed.

* Usually use first data set

* Write Formula

* Sub in #s with units

* Answer with units rounded off to the correct # of sig figs

Calculations:

D = M V

D = 5.40 g 2.0 ml

D = 2.7 g/ml

Conclusion It is the most important part of the lab

report.

It is where you tell me what you learned from the lab.

It always relates back to the purpose of the lab.

It should include a discussion of sources of error.

It is written in the third person.

It could suggest further investigations.

Conclusion: Different materials seem to have different densities. The five cubes have the same volume but their masses are different and consequently they have different densities. Aluminum, copper and lead have densities that are very different from each other. Of these three aluminum has the smallest density and lead has the largest density. Brass and iron have similar densities.

The density of the copper, brass, lead and iron cubes are exactly the same as the values reported in the CRC handbook of chemistry and physics. The density of aluminum should have been 2.7 g/ml. A source of error in this experiment is the measurement of the volume of the cubes using the water displacement method. When the cubes were dropped into the graduated cylinder water tended to splash out. This made the volume of the cube smaller than it really was and the density of the cube larger than the actual value. This would account for the measured density of aluminum being 3.0 g/ml.

Another experiment might be to measure the density of aluminum cubes that have different volumes. If the densities of these cubes were the same, density would be a characteristic property. A characteristic property allows one to distinguish substances regardless of the size of sample tested.

Conclusion Conclusion: Different materials seem to have different densities. The five cubes have the same volume but their masses are different and consequently they have different densities. Aluminum, copper and lead have densities that are very different from each other. Of these three aluminum has the smallest density and lead has the largest density. Brass and iron have similar densities.

The density of the copper, brass, lead and iron cubes are exactly the same as the values reported in the CRC handbook of Chemistry and Physics. The density of aluminum should have been 2.7 g/ml. A source of error in this experiment is the measurement of the volume of the cubes using the water displacement method. When the cubes were dropped into the graduated cylinder water tended to splash out. This made the volume of the cube smaller than it really was and the density of the cube larger than the actual value. This would account for the measured density of aluminum being 3.0 g/ml.

Another experiment might be to measure the density of aluminum cubes that have different volumes. If the densities of these cubes were the same, density would be a characteristic property. A characteristic property allows one to distinguish substances regardless of the size of the sample tested.

Sample Lab Report - Qualitative Data

  Raw Eggs and Chemicals

Purpose: TPOTLIT investigate the effects of chemicals on raw eggs.

Procedure: Sulfuric acid was added to a raw egg. In order to neutralize the acid, sodium hydroxide was then added. As a last resort, water was added to the raw egg.

Safety: #23, 26, 31

 Data:

Observations

Raw Egg Yellow yolk in center, 1” diameter Egg white clear, surrounding the yolk

Raw Egg with Acid Yolk congealed Egg white congealed and became opaque

Raw Egg with Base Egg became gel like

Raw Egg with Water Spread out the mixture

Conclusion: When the acid was added to the egg a chemical reaction occurred forming a white substance that was opaque. Although bases neutralize acids when the base was added the egg did not return to its normal state. This indicates that the acid was no longer present when the base was added because the acid had reacted with materials in the egg. Instead, the base reacted with the remaining material and formed a gel. This indicates that another chemical reaction occurred. The water was not able to return the egg to its “normal” state. The only effect of the water is to dilute the remaining chemicals. This activity demonstrated the meaning of the words “corrosive” and “caustic”. In a chemical sense these words mean “to destroy”. Since human eyes are made of protein materials just as the egg, this activity demonstrated the importance of always wearing safety glasses when performing labs.

F A Q’ S Yes, each person must record all data while performing the lab. Yes, all parts of the lab reports must be typed and each section clearly

labeled. Yes, each person must submit his/her own lab report. Yes, you may help each other with the calculations but each person

must work individually on the conclusion. NO, “warm and fuzzy” and personal comments are not included in the

lab report. Especially conclusions. ie “I really liked this lab. It was easy to do. I learned a lot about density.”

Yes, the lab report must be in the proper order. Reports are due on the following block lab day. Only one late lab report will be accepted a marking period. Yes, there is a 10 point penalty for each day that the report is late. EXTRA CREDIT: 10 point bonus if turned in before due date!

Lab Report MUST be complete.

Rubric for Lab ReportComponent Description Points

Title Clear and concise 1 point

PurposeOne sentence why the lab was performed

2 points

ProcedureOne paragraph summarizing how the lab was performed

2 points

Safety Rules cited by # 5 points

DataQualitative and quantitative observations

5 – 10 points

CalculationsSample calculation using problem solving technique

5 – 10 points

ConclusionAnalysis of what was learned from the lab including error analysis

20 – 30 points

Rubric for Lab Technique

Category Points

Participation in lab and Pre-Lab – Data – Post Lab Sheet

20 points

Accuracy of data 10 points

Adherence to safety rules 10 points

Cleaning of equipment and lab station 10 points

Laboratory Make-Up Policy

All labs are made up after school at 2:15PM on the following Thursday or Friday for Wednesday blocks

and Friday or Monday for Thursday blocks. If you are on a field trip on lab day, plan on making up the

lab that day at 2:15 PM.

If you miss a lab, see me to schedule make-up.

Once corrected labs are passed back to the class, late labs for that experiment can not be accepted.

Lastly

If you have questions or need help…

Please ASK!