Name: __________________________     Period: _________  Group #: _____________

 

DENSITY LAB    Std 4e

 

PURPOSE:

1. To calculate the different densities of several substances and become familiar with the use of calibrated metric or SI measuring instruments and their units.

 

                                         mass

                      density = ---------

                                       volume

 

2. To determine the level of accuracy by determining the percent of  experimental error.

 

                        value (from experiment) - theoretical value  (given by teacher)

% error =    --------------------------------------------------------------        x  100

                                       theoretical value

 

                (note:  vertical lines indicate absolute value)

 

MATERIALS:

10 ml & 50 ml graduated cylinders, metric ruler, thread, rectangular metallic object. irregular metallic object, water, methanol, corn oil, and centigram balance.

 

PROCEDURE 1:      Finding density of a rectangular piece of aluminum (Al)

1. Measure and .record the-length, width, and height of the aluminum.to the nearest tenth of a centimeter (0.1 cm).

2. Calculate and record the volume, and then the density. 

 

      Data Table 1 – Calculating the density of a rectangular Al object

 

             your measurements                                      calculations

 

      length _______________ cm                     volume ________________ cm3

      width _______________  cm                    density ________________  g/cm3

      height _______________ cm                     given density ___________  g/cm3

      mass ________________ g

 

      CALCULATIONS:   (show your work)

 

            Compare your measured density with the given (theoretical) value given in the information in Date Table for Procedure 1  and  calculate the percent error . 

 

 

PROCEDURE 2:        Find the volume of an irregularly shaped metallic object

 

1. Select an irregular object.  Note the symbol on the metal and then record the name of the element the metal is made from.

2. Mass the metal on the balance to the nearest hundredth of a gram (.01g) and record that mass in the data table below.

3.  Fill the 10 ml graduated cylinder with enough water so that your metal wilt be covered by water when immersed, but not too much, so that the volume of the water with the object in it may be read and recorded.

4. Read the level of the water at the meniscus and record that volume.

5. Immerse the massed metal.  Read the new level of water at the meniscus and record that volume.

6. Calculate the volume of the metal by subtracting the two water levels.

7. Calculate the experimental density of your metal and record it.  Look up and record the known theoretical density of your metal from the reference table.

8. Calculate the percent of experimental error and record it.

 

Data Table 2 – Density of an irregular metal object

 

Element object made from                                                  ____________________

Mass of metal (your massed)                                              _____________ g

Initial water level in graduated cylinder without sinkers _____________ ml  (cm3)

Water level with lead sinkers                                               _____________ ml  (cm3)

Volume of metal (calculated)                                               _____________ ml  (cm3)

Density of metal (calculated)                                               _____________ g/cm3

Theoretical density (given)                                                   _____________ g/cm3

Percent experimental error (calculated)                                _____________ % error

 

CALCULATIONS:  (show your calculations)

      volume of object  = 

 

 

      density of object =

     

      % error =

 

QUESTIONS:

 

1.  Whose principle did you employ to find the density of the objects? __________

 

2.  State at least two reasons why we have experimental errors (concentrate on the equipment we are using and the materials supplied)

 

PROCEDURE 3:   Determining the density of two liquids

 

1.   Measure the mass of a 10ml graduated cylinder to the nearest hundredth of a gram (.01 g). Do not change graduated cylinders throughout the experiment or it will affect your results.

2. Fill the graduated cylinder with 7-8 mL of water. (The second time you do this procedure you will be using Methanol instead of water.).  Read the volume of the liquid at the meniscus to the nearest tenth of a ml (0.1 ml).

3. Mass the graduated cylinder with the liquid and record. Be careful not to spill any of the liquid.

4. Calculate the experimental density of the liquid with the proper number of

      significant digits.

5. Look at theoretical density in Information Table 1 below (last page) and record the theoretical density for the liquid.

6. Calculate the % error.

7. When you are finished, be sure and wash out the cylinder with soapy water and

      rinse thoroughly.

 

DATA TABLE 3:  Calculating the density of two liquids

 

      mass  of 10 ml cylinder____________ g

 

 

Mass

 

Volume

Exp. Density

Theo. (from chart) density

 

% Error

cyl. & water   =        g

XXXXX

XXXXXX

XXXXXX

XXXXX

water (calc)    =        g

ml

g/ml

      g/ml

 %

cyl. & alcohol =       g

XXXXX

XXXXXX

XXXXXX

XXXXX

alcohol  (calc) =       g

ml

g/ml

g/ml

  %

 

CALCULATIONS:  (show your work)

 

      water density =                                                     % error = _________

 

      alcohol density =                                                   % error = _________

 

QUESTIONS:

 

1.   How does water’s density compare with alcohol?

 

 

2.   Give two reasons why there is a difference between the given density and the your calculated density (concentrate on the equipment you had to use) .

 

 

PROBLEMS:   (show your work)  

After doing this lab and completing the chart, you should be able to do these problems:

1.   What is the volume of 66.6 g of magnesium (Mg) if it has a density of 1.74 g/cm3 ?

 

 

 

 

2.   Tin (Sn) has a density of 7.28 g/cm3.  What is the volume of 4.32 kg of Sn?

 

 

 

 

3.  What is the mass of 3.00 m3 of nitrogen gas (N2) if its density is 1.25 g/dm3 ?

 

 

 

 

 

 

 

 

Information Table 1     THEORETICAL (precise to 2 decimals)

Known Densities of Some Common Materials

Zinc (Zn)               7.14 g/cm3                           Pure Water           1.00 g/cm3

Copper (Cu)         8.92 g/cm3                           Methanol              0.78 g/cm3 

Aluminum (Al)       2.70 g/cm3                           Corn oil                0.93 g/cm3 

Iron (Fe)               7.89 g/cm3 

Tin (Sn)                7.27 g/cm3 

Lead (Pb)           11.34 g/cm3

 

                         Biography - Archimedes (287-212 BC)

Archimedes was a Greek mathematician and scientist who made discoveries about the behavior of solids and liquids, and unlike other Greek philosophers- at the time, he actually tested his ideas. One of his most  famous discoveries was the method of measuring the volume of an object. He did so by measuring the  volume of water that the object displaces. Legend has- it that he developed this method of measurement when he was asked to find a way to detect if the crown of the King of Sicily was made of pure gold, because the King suspected his goldsmiths had made it from something other than gold. When taking a bath he realized how he could determine the volume of the crown, and thus he was then able to identify the metal from its density after determining the mass.