lab1

Density of Rubber and Four Pure Metals

Introduction:

1) Density is an important feature of matter and is equal to its mass per unit volume. (d = m/V)

2) The SI unit for density is kg/m3.

a. This unit of measure is not practical so the conversion is made to g/cm3.

b. kg/m3 = (1000g/1kg) x (1m)3/(10dm)3 x kg/m3 = g/cm3.

c. In addition, 1cm3 = 1mL, so density can be reported as g/mL.

3) This property of matter can help identify unknown substances.

a. If the mass and volume are measured, the density can be calculated.

4) Since density is characteristic of a substance, it can help assess purity.

a. The purity of a substance can be assessed by comparing the determined value to the actual value of density.

5) The density is a conversion factor between mass and volume.

6) Density is an intensive property of matter.

a. Intensive properties are independent of the amount of a substance.

b. Extensive properties depend on the amount of a substance such as mass, volume, and moles.

Substances to include in the Table of Chemical and Physical Properties:

The density of the following substances: zinc, copper, nickel, lead, polypropylene (rubber), water.

Procedure for Part 1: Density of Rubber Stoppers

1) Add 50.0 mL of distilled (or deionized) water to a 100.0 mL graduated cylinder.

a. Measure the exact volume of water added to the nearest tenth or first decimal place.

2) Place graduated cylinder onto a top-loading balance.

a. Once a stable mass is displayed, tare the balance (or set the mass to zero).

3) Obtain a combination of 5 rubber stoppers with sizes of 00, 0, 1, and/or 2.

4) Add one stopper at a time to the graduated cylinder and record the mass (or cumulative mass) of the stopper(s), the total volume to the nearest tenth, and the volume of water displaced.

a. Be careful not to splash out any of the water.

b. Record the mass indicated on the balance using all decimal places provided.

5) Continue to add rubber stoppers (without removing the previous ones) and record the cumulative masses, total volumes to the nearest tenth, and volumes of water displaced.

6) Graph the cumulative mass versus the cumulative volume displaced using a computerized graphing program.

a. The mass should go on the y–axis and the volume displaced should be placed on the x–axis.

b. Ensure that the plot has an appropriate title and both axes are labeled with the variables and units.

c. If using Microsoft Excel or a similar computerized program, ensure that all major and minor gridlines are turned on.

d. Have the program draw the best fit straight line using a linear regression.

i. Do NOT just connect all the points!

ii. Have the program report the equation for the line on the graph using the following generic formula: y = mx + b.

e. The density of the material is the slope of the line indicated by the coefficient of x.

i. If the equation is not available, to calculate the slope, choose two points that fall on the line and calculate the change in y over change in x via the formula: (y2 – y1)/ (x2 – x1).

Procedure for Part 2: Density of Four Pure Metals

1) Place 15.00 mL of distilled (or deionized) water into a 25.00 mL graduated cylinder (that is marked with 0.2 mL increments.)

a. Measure the exact volume of water added to the nearest hundredth or second decimal place.

2) Place graduated cylinder onto a balance.

a. Once a stable mass is displayed, tare the balance (or set to zero).

3) Carefully, place approximately 5 grams of the first metal into the graduated cylinder.

f. Record the mass (or cumulative mass) of the metal, the total volume to the nearest hundredth, and the volume of water displaced.

g. Be careful not to splash out any of the water.

4) Without removing the previous mass, add enough metal to bring the cumulative mass to ~10 grams.

a. Record the mass (or cumulative mass) of the metal, the total volume to the nearest hundredth, and the volume of water displaced.

b. If you overshoot the mass, do not remove anything from the graduated cylinder. Record the mass (or cumulative mass) of the metal, the total volume to the nearest hundredth, and the volume of water displaced.

5) Continue adding for mass amounts of ~12 grams, ~15 grams, and ~20 grams.

a. Record the cumulative mass of the metal, the total volume to the nearest hundredth, and the volume of water displaced.

b. If you overshoot the mass, do not remove anything from the graduated cylinder. Record the cumulative mass of the metal, the total volume to the nearest hundredth, and the volume of water displaced.

6) Repeat the above experiment with the other three metals.

a. The metals that you will use are: copper, lead, nickel, and zinc.

b. Be careful pouring out the lead; it is easy to spill.

7) Graph the cumulative mass versus the cumulative volume displaced using a computerized graphing program.

a. The mass should go on the y–axis and the volume displaced should be placed on the x–axis.

b. Ensure that the plot has an appropriate title and both axes are labeled with the variables and units.

c. If using Microsoft Excel or a similar computerized program, ensure that all major and minor gridlines are turned on.

d. Have the program draw the best fit straight line using a linear regression.

i. Do NOT just connect all the points!

ii. Have the program report the equation for the line on the graph using the following generic formula: y = mx + b.

e. The density of the material is the slope of the line indicated by the coefficient of x.

i. If the equation is not available, to calculate the slope, choose two points that fall on the line and calculate the change in y over change in x via the formula: (y2 – y1)/ (x2 – x1).

c. Look up the true value for each metal and compare.

i. Using proper bibliographic technique, cite references for sources of true values.

Clean–Up:

1) Without allowing any of the metal fragments to fall into the drain, dispose of the water down the sink.

2) Dry off the metal fragments and place them in the labeled waste containers.

3) Stoppers should be dried off and returned to their storage bins.

Model Data Table:

Mass and Volume Measurements for Zinc Metal

Cumulative Mass of Metal (g) (y –axis on graph)	Total Volume of Water (mL)	Volume Displaced (mL) (x –axis on graph)
0	15.00	0
5.2289	16.45	1.45
10.1625	17.80	2.80
12.9912	18.40	3.40
14.8920	18.95	3.95
21.2055	19.80	4.80

Draw the best fit straight line and the density will be the slope of the graph: Δy/Δx.

Data Tables:

Mass and Volume Measurements for Rubber Stoppers

Stopper Size(s) (00, 0, 1, or 2)	Cumulative Mass of Stoppers (g) (y –axis on graph)	Total Volume of Water (mL)* *to tenth place	Volume Displaced (mL) (x –axis on graph)
	0.00		0.0

Experimental/Observed Density for Rubber: _________ g/mL

True/Theoretical Density for Rubber: _________ g/mL

Percent Error for Rubber Density: _________ %

Mass and Volume Measurements for Copper

Approximate Mass (g)	Cumulative Mass of Metal (g) (y –axis on graph)	Total Volume of Water (mL)* *to hundredth place	Volume Displaced (mL) (x –axis on graph)
0	0.0000		0.00
~5
~10
~12
~15
~20

Experimental/Observed Density for Copper: _________ g/mL

True/Theoretical Density for Copper: _________ g/mL

Percent Error for Copper Density: _________ %

Mass and Volume Measurements for Lead

Approximate Mass (g)	Cumulative Mass of Metal (g) (y –axis on graph)	Total Volume of Water (mL)* *to hundredth place	Volume Displaced (mL) (x –axis on graph)
0	0.0000		0.00
~5
~10
~12
~15
~20

Experimental/Observed Density for Lead: _________ g/mL

True/Theoretical Density for Lead: _________ g/mL

Percent Error for Lead Density: _________ %

Mass and Volume Measurements for Nickel

Approximate Mass (g)	Cumulative Mass of Metal (g) (y –axis on graph)	Total Volume of Water (mL)* *to hundredth place	Volume Displaced (mL) (x –axis on graph)
0	0.0000		0.00
~5
~10
~12
~15
~20

Experimental/Observed Density for Nickel: _________ g/mL

True/Theoretical Density for Nickel: _________ g/mL

Percent Error for Nickel Density: _________ %

Mass and Volume Measurements for Zinc

Approximate Mass (g)	Cumulative Mass of Metal (g) (y –axis on graph)	Total Volume of Water (mL)* *to hundredth place	Volume Displaced (mL) (x –axis on graph)
0	0.0000		0.00
~5
~10
~12
~15
~20

Experimental/Observed Density for Zinc: _________ g/mL

True/Theoretical Density for Zinc: _________ g/mL

Percent Error for Zinc Density: _________ %

Banerjee

General Chemistry-I Lab