Experiment 1 Mass Volume and Density

Name Partner(s) (2 pt penalty) Experiment 1: Mass Volume and Density In-Lab Notebook (Results and Observations) Record your general measurements, recorded data and observations directly into this section during the lab. Data can be transcribed directly into the tables provided below. Add titles and captions to all tables and figures for full credit. Remove and replace any highlighted text.      Present your data in the figures and tables below.*If you collected more data than the template tables allow, you can add more rows. Summarize your observations during the progress of the experiment. Observations should not include numbers (measurements). Tables should be accompanied by a caption which helps the reader understand what the data means and what conclusions can be drawn from the data in the table. Always fill in units in tables - in parentheses below. To avoid confusion, do not add units to numbers, but instead to data headers or labels (such as what was done in the Excel tutorial) Add observations between data tables to log what you see during the experiment (1-2 sentences is usually sufficient for any major steps - i.e. the volume increased noticeably when...) TABLES 1 & 2 (4) Table 1. Preliminary Measurements for Experiment 1 Trial 1 Type of sample (distilled, contaminated, purified water) Buret segment mass (units): Buret segment mass with sample (units): Mass of sample (units): Largest volume Increment, V b(units): Initial Volume reading, Vi (units): Volume reading with thermometer, Vt(units): Displacement Volume, Vd(units): 1 Trial 2 Purified Purified 19.83 g 24.04 g 4.21 g 50.00 mL 45.30 mL 45.10 mL 0.20 mL 19.83 g 23.99 g 4.16 g 50.00 mL 45.80 mL 45.40 mL 0.40 mL Fall 2019 Table 2. Data Observations for Experiment 1 Corrected Temperature Corrected Density (g/mL) Volume (mL) (ºC) Volume (mL) Trial 1 Trial 1 Trial 1 Trial 2 Temperature Density (g/mL) (ºC) Trial 2 Trial 2 4.70 mL 80.0 ºC 0.896 g/mL 4.70 mL 80.0 ºC 0.885 g/mL 4.60 mL 66.2 ºC 0.915 g/mL 4.60 mL 55.5 ºC 0.904 g/mL 4.10 mL 54.6 ºC 0.936 g/mL 4.50 mL 40.7 ºC 0.924 g/mL 4.10 mL 41.4 ºC 0.936 g/mL 4.50 mL 32.3 ºC 0.924 g/mL 4.10 mL 32.0 ºC 0.936 g/mL 4.50 mL 28.1 ºC 0.924 g/mL FIGURES 1 & 2 (6) Figure 1. This figure shows the negative relationship between density of water and temperature for our experimental data. It shows this relationship for two separate trials and both show that as temperature increases, density decreases. 2 Fall 2019 Figure 2. This figure shows the negative relationship between density of water and temperature. The trend shows that as temperature increases, density decreases. It shows the values as listed in the CRC Press Handbook of Chemistry and Physics. TABLE 3 (4) Table 3. Experimental Graph Data vs. Literature Value Graph Data 2nd Trial First Trial Literature Values (Experimental) (Experimental) 2 Coefficient of determination, R 0.8138 0.9521 0.9922 y-intercept 0.9697 0.9512 1.0115 Slope -8*10-4 -8*10-4 -5*10-4 Slope % error (exp vs. literature) -60% -60% 0% 3 Fall 2019 TABLE 4 (6) Make sure to have original titles for your figures that explain results. Table 4. Group Data Breakdown for Three Types of Water Samples Density Mean Slope of at room density temp. Mean Type of CV % temp. dependen slope Group at Sample (units) diff. ce (g/mL/ (units) (25 ºC; room temp g/mL) ºC) 1 0.088 -5.2*10-5 2 0.999 -7.5*10-4 0.693 -8.0* Distilled 75.6 30.5 10-4 g/mL 3 0.993 -1.6*10-3 4 5 0.990 -1.6*10-3 6 0.977 0.993 -1.6*10-3 -1.6* Contam. 1.37 0.401 g/mL 10-3 7 0.993 -1.6*10-3 8 1.01 -1.6*10-3 9 0.985 -8.0*10-4 10 1.01 0.995 -1.2*10-3 -1.2* 1.08 0.201 Purified g/mL 10-3 11 0.991 -1.1*10-3 12 0.992 -1.6*10-3 CV (units) % diff. -96.9 -60.0 0 -220 -27.5 -140 TA ONLY: Performance Points Post-Lab Analysis (Calculations, Discussion and Conclusions) Provide sample calculations for each sample requested in the space below. Answer the discussion questions within the limit provided. SAMPLE CALCULATIONS (20) Equation must be expressed algebraically, with clear labels, and one example with substituted numbers and units. - Mass of water: volume * density  ex, 4.70 mL*0.896 g/mL = 4.21 g - Corrected volume: Vb - Vt - Vd  ex, 50.00 mL - 45.10 mL - 0.20 mL = 4.70 mL - Density: mass / volume  ex, 4.21 g / 4.70 mL = 0.896 g/mL - % error: [(|reference value - mean of measurements|) / (reference value)] * 100  ex, [(|-.0005-(-.0008)|) / (-.0005)] * 100 = -60 % -CV: 100 * (standard deviation / mean)  100 * (0.010786 / 0.995) = 1.08 4 Fall 2019 Post-Lab Discussion Questions Questions should be answered in complete sentences directly after a question. You should only need 1-2 sentences to answer each question. 1. (6) Make sure to post your data on the shared google sheet within 48 hours of the end of lab. (TAs will confirm timestamps.) 2. (6) Do the values obtained by the class support the literature values? Use specific numbers from your data tables above to support your answer. The class values support the literature values in some ways and not others. For example, the purified water samples had the closest mean density at room temperature (0.995 g/mL) to the literature values (0.997 g/mL), as expected. Unexpectedly, the distilled sample appears to have the closest mean slope (-8.0*10-4) to the literature values slope (-5.0*10-4). If the class data fully supported the literature values, we would expect the purified samples to have the closest mean slope to the literature values. 3. (4) Based on Figures 1 and 2, what is the relationship between density and temperature? According to Figures 1 and 2, density decreases as temperature increases. 4. (6) Why does density change with temperature? (Consider what is happening at a molecular level.) Do not copy/paste from an external source. Explain this in your own words. Include a citation if necessary. The higher the temperature of a substance, the faster molecules are moving and more spread out they are. This “spreading out” increases the volume of the substance, because it is taking up more space but not necessarily changing in mass. Because density = mass/volume, increasing the value of volume will decrease the value of density. So, when temperature rises, volume increases, which causes density to decrease. 5. The coefficient of determination, R2, can range between boundary values of 0 and 1. Values closer to 1 indicate a better fit of a linear trend line to the experimental data points. o (3) Consider the density of your samples: Do you predict the data would be completely linear from 0 to 100ºC, why or why not? I do not think the data would be completely linear from 0 to 100 ºC. Density appears to be decreasing faster the higher the temperature gets, so there is no constant rate of change or slope. 5 Fall 2019 o (4) Based on your values in Table 3, did the experimental or literature density values better fit the linear trend? Postulate a reason for this. Based on the values in Table 3, the literature density values fit better in the linear trend. I believe this is because the literature values were probably derived from more controlled experiments containing less systematic and/or random errors. o (4) What does R2 represent in a general sense? How should it be interpreted? In a general sense, R2 represents how close data points are to a trend line. It can be interpreted as a value that tells you how firm the relationship between your two variables on a graph are. 6. (5) Think about sources of error within this experiment. Besides human error (inability to read clearly, spilling, etc), what are possible sources of error? Define these as systematic or random. Besides random human errors like misreading the buret or electronic balance measurements, sources of random error in this experiment could be the temperature or pressure of the room, which may have unexpected effects on data values. Sources of systematic error could be improperly calibrated electronic balances, thermometers, or buret segments. o (5) When you measure the mass of the water, you use 4 significant figures. Why is the reported density only given in 3 significant figures? Because our volume measurements have 3 significant figures and determining density requires division of mass and volume, the reported value will have 3 significant figures. This is because it can have no more significant figures than the item in the operation with the smallest number of significant figures. 7. Consider the last three columns of Table 4, and answer the following questions: o (3) How well do the measurements of distilled water reproduce the literature values? (Remember to cite specific data.) The measurements of distilled water show a similar slope (-8.0*10-4) to the literature values (-5.0*10-4). Though it has the smallest % difference compared to the literature values, it has the highest CV. This means the data varies a lot around the mean, so more tests may be needed to support this observation. 6 Fall 2019 o (3) How different are the densities of the contaminated and purified water from distilled water? The densities of the contaminated (0.993 g/mL) and purified water (0.995 g/mL) are quite different from that of distilled water (0.693 g/mL). This could be due to experimental error, but as it stands there is a 30.3% difference between them. o (3) How well do different groups' measurements of the same type of water sample reproduce each other? The groups with contaminated and purified samples seemed to reproduce each other’s results consistently, with a standard deviation of only about 0.01 for each group. The groups with distilled samples seemed to have a harder time reproducing each other’s results, with a standard deviation of about 0.52. CONCLUSIONS (8) Write a brief (1-2 sentence) conclusion making the strongest statement you can make relating your experimental results to the purpose statement developed in your pre-lab. I believe that density can be used, at least in part, to determine the effectiveness of water purification tablets. Our experimental results show that the purified water samples had the closest density to values present in accepted literature for the standard density of pure water. TA ONLY: Formatting Late Penalty 7