Predicting the Density of an Element
Predicting the Density of an Element
Background
The periodic table is not random in its arrangement. Elements are arranged by increasing atomic number and elements with similar properties are placed in the same group. As we moved across a period (or row) or down a group (or column) certain properties change in predictable ways. Since the change is predicable, we can gather information about a few elements in a group and use this to make predictions about other elements in the same group. In this lab we will find the density of three elements in Group 14 and then use this information to predict the density of a fourth element in the same group.
Purpose
To determine the density of germanium using periodic properties.
Materials
electronic balance
weighing dishes
10 g sample of tin
25 g sample of lead
5 – 10 g sample of silicon
25-mL graduated cylinder
graph paper
Procedure
1. Place a weighing dish on the electronic balance. Tare the balance so that the reading on the balance is zero.
2. Place the metal sample in the weighing dish. Record the mass of the sample in the data table.
3. Place approximately 15 mL of water in the graduated cylinder. Measure the volume of water to the nearest 0.1 mL. Record the volume in your data table.
4. Carefully place the metal sample in the graduated cylinder with the water. Measure and record the volume of the water and the metal sample.
5. Repeat steps 1 – 4 for the other two metal samples.
Calculations
1. Subtract the volume of water from the volume of water and the metal sample to obtain the volume of the metal alone. Record this volume in your data table.
2. Calculate the density of each metal sample. Remember: Density is mass divided by volume. Show all of your work in the space below. Record your final density value in the data table.
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Silicon Tin Lead
3. Find the period number for each metal and record in the data table.
4. Make a line graph that shows the relationship between the densities of the metals and the periods in which they are located in the periodic table. Place the number of the period (from 1 to 7) on the horizontal axis and the density (in g/mL) on the vertical axis. Draw a straight line that comes as close as possible to all three points.
5. Germanium is in Period 4. To estimate the density of germanium, draw a dotted vertical line from the 4 on the horizontal axis to the graphed line. Then, draw a dotted horizontal line from the solid line to the vertical axis. Read and record the density of germanium.
Data Tables
|Metal |Mass (g) |Volume of Water (mL) |Volume of Water + Metal Sample |Volume of Metal Sample (mL) |
| | | |(mL) | |
| | | | | |
| | | | | |
| | | | | |
|Metal |Period Number |Density (g/mL) |
| | | |
| | | |
| | | |
Analysis and Conclusions
1. What is the density of germanium based on your graph? (Be sure to include units!) ____________
2. List lead, silicon and tin in order of increasing density.
3. Use the formula shown below to calculate a percent error for the density of germanium. The actual value for the density of germanium is 5.3 g/mL.
4. How does the density of the elements change from silicon to lead in Group 14?
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