2. Lab Reports Everything You Didn’t Want to Know!

3. Components of a Lab Report Title Purpose Procedure Safety Data Calculations Conclusion

4. 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 physics equation Safety: Specify safety rules 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: Beware of glass cuts Wipe up any spills immediately

5. 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 9.0 brass 15.60 2.0 7.8 lead 22.80 2.0 11.4 iron 15.80 2.0 7.9 Data

6. 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

7. 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.

8. 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.

9. 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.

10. Lastly If you have questions or need help… Please ASK!