The Periodic Trend of Density Or What S Up/Down with That Group?

The Periodic Trend of Density or What’s up/down with that Group?

Purpose: To investigate the physical property of density (D=m/v).

To determine if there is a periodic trend for density.

Background: When elements are arranged in order of increasing atomic number they exhibit a periodic trend for different properties. The elements in a horizontal line across the periodic table are in the same period. As elements are analyzed in a vertical line down the periodic table they are in a group (family). The similar physical and chemical properties for a family of elements are due, in large part, to the fact that all of the elements within a group/family have the same number of valance electrons and electron configuration pattern. In this experiment it will be determined if density is a physical property that can be considered as a periodic trend.

Procedure: Obtain the three metal samples Lead (Pb), Silicon (Si), and Tin (Sn). Mass one dry metal sample and record the mass in the quantitative data table. Observe the physical properties of the three samples and record observations in the qualitative data table.

Fill a graduated cylinder with water (about half full), record the exact volume in the quatitative data table. Gently slide the metal sample down the side of the tilted cylinder so that no water splashes out and the metal does not hit the bottom of the cylinder and break it. Now record the exact final volume of water with metal submerged in the quantitative data table. Record your qualitative observations.

Now carefully pour out the water and place the metal sample on a paper towel to dry, record your qualitative observations for any changes in the metal.

Repeat the procedure with the other two metal samples.

Quantitative Data Table

Lead (Pb) Silicon (Si) Tin (Sn) Mass of Metal (g) Volume of water alone (mL) Volume of water + metal (mL)

Qualitative Dat Table

Observations Lead (Pb) Silicon (Si) Tin (Sn) Before During After Calculations: Show one sample calculation for one type of metal. DO NOT show all the work for all three metals. A calculation consists of a statement, a formula, a number set up and a final answer. Do not forget significant digits and round correctly.

1. Calculate the volume of the metal sample.

Volume of water + metal (mL) - Volume of water (mL) = Volume of metal (mL)

1 mL is equal to 1cm3

2. Calculate the density of the metal sample.

Density = mass (m)/volume (V)

Results Table:

Lead (Pb) Silicon (Si) Tin (Sn) Volume of metal (cm3) Mass of metal (g/cm3)

Graph:

Make a graph plotting Density (y) vs. Period Number (x).

You can make the graph using the graphical analysis/logger pro or excel/Microsoft office on the computers or you can make the graph by hand. Be sure to label the “x” and “y” axis and give the graph a title. The grid should have equal distribution of numbers along both the x and y axis.

Questions:

1. Estimate the density of Germanium (Ge), using your graph.

2. Explain how the density of Germanium form the graph compares to the actual density of Germanium (5.46g/cm3).

3. Calculate the percent error between your estimated value for the density of Germanium and the theoretical value for the density of Germanium.

Formula: % error = (Theoretical value- Estimated (experimental) value) X 100

Theoretical Value

Number Set Up: % error = ( 5.46g/cm 3 - Estimated (experimental) value) X 100

5.46g/cm3 Answer: %error = %

4. Is density a physical property of a substance? Defend your answer with an explanation.

Conclusion:

Restate the purpose (1-2 sentences)

Brief procedure (1-2 sentences)

Discussion of theory and what was learned in the laboratory experiment. Discuss the results. Incorporate new terms into the discussion (the background sections may provide some assistance). (4-5 sentences)

Sources of error: there must be two possible errors discussed. These would be errors that could have occurred during the procedure of the experiment. Finally the effect that the error would have on the final results for density must be explained. (through 2-4 sentences).