Name: ______________________________ Period: _____ Date: _______________ Lab: Density of an Unknown Solid Problem: How do you determine the identity of a substance using the density of the solid? Objectives: Students will calculate and measure the volumes of unidentified cylinders Students will measure the masses of unidentified cylinders Students will calculate the densities of unidentified cylinders Students will use calculated densities to identify the cylinders’ elements. Students will compare their calculated densities to the given density values and calculate the error and percent error. Students will plot the relationship between atomic number and density to determine if there is a density trend in the perioidic table Students will plot the relationship between atomic mass and density to determine if there is a relationship between them. Equations: Density = mass / volume Volume of cylinder; v = πr2h Error = Accepted Value – Calculated Value Percent Error = (Accepted Value – Calculated Value) / Accepted Value Hypothesis: 1.) Can you determine the identiy of an unknow metal from its density? Why or Why not? ______________________________________________________________________________________________ ______________________________________________________________________________________________ ______________________________________________________________________________________________ 2.) Will the densities you determine be within 10% error to the accepted values? Why or Why not? ______________________________________________________________________________________________ ______________________________________________________________________________________________ ______________________________________________________________________________________________ Procedure: 1. Obtain the four metal cylinders and record their physical description in the table below 2. Measure the mass of each cylinder and record it in the table below 3.Fill a PLASTIC 100 mL graduated cylinder with 50 mL of water. Record this as your INITIAL water volume. If you have more or less than 50 ml, record your exact initial volume in ml. 4. Convert the volumes from ml to cm3. Record the cm3 value in the space below 5. Gently slide the first metal cylinder into the graduated cylinder and read the volume of water. Record this as your FINAL water volume in ml. Then convert it to cm3. 6. Calculate the displacement of the water (the CHANGE in water level.) This is the VOLUME occupied by the metal cylinder. Record this value in cm3. 7. Dry the metal cylinder and measure its radius and height in cm. Round to the nearest 0.1 cm. Record this in the space below. Then place the cylinder back in the bag. 8. Repeat steps 3-7 for each of the four cylinders. 9. Calculate the densities for each of the four cylinders both with you measured volume and you calculated volume. 10. Compare the densities you calculated to the accepted values table. Identify the unknown samples using the value that most closely matches the one you calculated. Name: ______________________________ Period: _____ Date: _______________ Results Cylinder Physical Description of Cylinder Mass in grams Initial Volume of Water in ml Final Volume of Water in ml Initial Volume of Water in cm3 Final Volume of Water in cm3 Water Displacement in cm3 Volume of Cylinder Measured in cm3 Radius of Cylinder in cm Height of Cylinder in cm Volume of Cylinder Calculated in cm3 Density with measure volume Density with calculated volume Identity of unknown cylinder based on density Error Table density – calculated density Percent error Error/ Table Density A C L Z Name: ______________________________ Period: _____ Date: _______________ Element lithium beryllium boron carbon sodium magnesium aluminum silicon potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium rubidium strontium silver cadmium indium tin cesium barium platinum gold mercury thallium lead Atomic Number 3 4 5 6 11 12 13 14 19 20 21 22 23 24 25 26 27 28 29 30 31 32 37 38 47 48 49 50 55 56 78 79 80 81 82 Density Atomic mass 0.53 1.85 2.34 2.26 0.97 1.74 2.7 2.33 0.86 1.55 2.99 4.54 6.11 7.19 7.44 7.874 8.9 8.9 8.96 7.13 5.91 5.32 1.532 2.54 10.5 8.65 7.31 7.31 1.87 3.59 21.45 19.3 13.55 11.85 11.35 6.941 9.01218 10.811 12.011 22.98977 24.305 26.98154 28.0855 39.0983 40.078 44.9559 47.88 50.9415 51.996 54.938 55.847 58.9332 58.6934 63.456 65.39 69.723 72.61 85.4678 87.62 107.868 112.41 114.82 118.71 132.9054 137.33 195.08 196.9665 200.59 204.383 207.2 Discussion questions: Answer all questions on a separate sheet of loose leaf and attach it to this lab. Graphing question should include a graph drawn on the graph paper provided. 1. Why is density considered an intensive property and volume and mass are considered extensive properties? 2. Was there a difference in the volume you measured with the graduated cylinder and the one you determined using geometry? If so what would account for those differences? 3. Did the cylinders have equal volume or mass? 4. What caused the cylinders to be different densities? 5. What happens to the density as the volume increases? 6. What happens to the density as the mass increases? 7. Using the table, create a graph of the relationship between atomic number and density. Is there a relationship? If so what is it? Is there a periodic trend evident? If so what is it? 8. Using the table, create a graph of the relationship between atomic mass and density. Is there a relationship? If so what is it? 9. Using the data from your table, Graph Volume vs Density. What Type of relationship is this? 10. Using the data from your table: Graph Mass vs Density. What Type of relationship is this? 11. Would any of these sample float in water? Why or why not? 12. Given that the density of water is 1.00 g/mL and the density of ethylene glycol (antifreeze) is 1.114 g/mL, if 100.0 mL of water is combined with 10.0 mL of ethylene glycol, which liquid would you expect to float on top? Draw a picture to support your answer.