lab+1+density+a+characteristic+property


 * Cullen Orengo **


 * __ Title: __** Lab 1 Density: A Characteristic Property


 * __ Purpose: __** The purpose of this lab is to discover how density can be used to identify various substances.
 * Teacher Comment: More detail needed. Tell what will be done in the lab. **
 * __ Materials: __**
 * Milligram balance
 * Small beakers, 20-30 mL or similar (4)
 * 1 ml volumetric pipets (4)
 * Pipet filler bulb
 * Sample vials, with caps (12 if possible)
 * Safety goggles.
 * Hexane acetone
 * Unknown liquid
 * 10-mL graduated cylinder (in small, capped bottles)
 * Silicon, small pieces to fit in graduate
 * Tin, granular or small pieces; not foilwater (tap or distilled/deionized)

§ Goggles on at all times. § Open flames should be used with caution. § Avoid breathing in vapors from the liquids. § Wash your hands with soap and water after. In part A first label and weigh each vial. Then fill each vial with 1 mL of another liquid. Next weigh the vials with caps containing the liquid. Repeat these steps for the next liquid. For part B, first weigh the container of the solid. Then fill a 10 mL graduated cylinder about half way. Next add enough solid to raise the water by at least 1.0 mL. The mass of the solid that was placed in the cylinder is found by subtracting the original weight of the solid from the new mass of the cylinder. Volume is found by subtracting the second water level by the first water level.
 * __ Safety: __**
 * __ Procedure: __**


 * Liquid || Acetone || Hexane || Unknown ||
 * Mass of empty vial and cap || 26.581g || 25.952g || 26.615g ||
 * Mass of vial, cap, liquid || 27.737g || 26.591g || 27.407g ||
 * Mass of liquid || 1.156g || .639g || .792g ||
 * Volume of liquid || 1.0 mL || 1.0 mL || 1.0 mL ||
 * Teacher Comment: Volume should be to 1.000 ml. You have now limited your sig figs for all of part A. **


 * Liquid || Acetone || Hexane || Unknown ||
 * Mass of empty vial and cap || 26.391g || 25.823g || 26.934g ||
 * Mass of vial, cap, liquid || 27.613g || 26.424g || 27.752g ||
 * Mass of liquid || 1.222g || .601g || .819g ||
 * Volume of liquid || 1.0 mL || 1.0 mL || 1.0 mL ||


 * Liquid || Acetone || Hexane || Unknown ||
 * Mass of empty vial and cap || 26.591g || 25.763g || 26.712g ||
 * Mass of vial, cap, liquid || 27.701g || 26.393g || 27.493g ||
 * Mass of liquid || 1.100g || .630g || .783g ||
 * Volume of liquid || 1.0 mL || 1.0 mL || 1.0 mL ||

§ **__ Pre lab: __** 1) .750g/mL - .735 g/mL= .015 g/mL/.750 g/mL=.02= 2% error

2) 3.51 g/cm3 + 1.55 g/cm3 = 5.06 g/cm3/2=2.53 g/cm3 is the expected density of strontium. Accepted value is 2.63g/cm3 2.63 g/cm3-2.53 g/cm3=.1 g/cm3/2.63 g/cm3=.038. 3.1% error  3) 1.00 cm3 of strontium has a mass of 2.63g. 1 m3 of strontium has a mass of 263 g. this questions illustrates that density is an intensive property because when calculated, the density will be the same for both sets of measurements.

4a) 2.70g/cm3 x 1 lb./453.6g x (2.54cm/1 in)3 =.098 lb./in3 is the density of aluminum. .997g/cm3 x 1 lb./453.6g x (2.54cm/1 in.)3 = .036 lb/in3 is the density of water.  b) The specific gravity of aluminum is the same regardless of the units used because 2.7g/cm3/.997g/cm3 is 2.7 and .098lb/in3/.036lb/in3 is 2.7.


 * __ Analysis and conclusions: __**

1) Acetone trial one: 1.156g/1.0mL=1.156 g/mL Trial two: 1.222g/1.0mL=1.22 g/mL  Trial three: 1.100g/1.0mL=1.100 g/mL  Mean density: 1.156 g/mL+1.222 g/mL+1.100 g/ml= 3.478g/mL/3=1.159 g/mL  .063  .059 || .042 || .022  .007 || .015 || .021  .015 || .014 ||
 * Liquid || Density || Density || Density || Density || Individual deviation || Average deviation ||
 * || Trial 1 || Trial 2 || Trial 3 || mean ||  ||   ||
 * Acetone || 1.156 g/mL || 1.222 g/mL || 1.100 g/mL || 1.159 g/mL || .003
 * Hexane || .639 g/mL || .601 g/mL || .630 g/mL || .623 g/mL || .016
 * Unknown || .792 g/mL || .819 g/mL || .783g/mL || .798 g/mL || .006


 * Teacher Comment: Deviation has units. **

2) Uncertainty || Accepted  Density || Accurate?  Y/N || Precise  Y/N || 3) The Uncertainty for acetone is .042/1.159=.0362= 4% uncertainty for acetone. The Uncertainty for hexane is .015/.623=.024= 2% uncertainty for hexane. The Average uncertainty is 4%+2%=6%/2= 3% is the average uncertainty. The Uncertainty range for unknown is .774 g/mL-.822 g/mL The unknown liquid is ethyl alcohol
 * Liquid || Density +/-
 * acetone || 1.159 g/mL +/- .042 g/mL || .791 g/mL || No || No ||
 * hexane || .623 g/mL +/- .015 g/mL || .659 g/mL || No || No ||
 * Unknown || .798 g/mL +/- .014 g/mL ||  ||   || No ||


 * Teacher Comment: Should give all in the accepted range. **

4) Organic liquids can have a large range of densities. Most have densities that are less than the density of water. The organic liquids with densities greater than that of water contain elements other than carbon, hydrogen, and oxygen, like chlorine or iodine. 5) The density of silicone is 3.973g divided by 1.0 cm3 so the density to the correct number of significant figures is 4.0 g/cm3. The density of tin is 2.109 g divided by 1.0 cm3 so the density is 2.1 g/cm3. The uncertainty is (0.2/1.0) which is 20%. 6) The expected density of germanium would be (4.0 g/cm3 + 2.1g/cm3)/2 which equals 3.1 g/cm3 +/- 20%. 7) The accepted density of germanium is 5.323 g/cm3. The accepted value does not fall within my uncertainty range. My percent error is (5.323 g/cm3 – 3.1 g/cm3)/5.323g/cm3 which equals a 42% error. 8a) Mendeleev would predict that the density of gallium would be (2.70 g/cm3 + 7.31 g/cm3)/2 which is 5.01 g/cm3. b) The relative error between the expected an observed values is
 * Teacher Comment: kind of trails off here. **

The calculations show that it was not very accurate or precise method in measuring the gram values for the experiment. This experiment works because it shows how important accuracy and precision are in the lab. The theory demonstrated in the lab was that density is a characteristic property and can be used to correctly identify substances. The percent error was high at 41% as my results were generally less than the accepted values. Two sources of error could be that the scales could have been thrown off by an outside force like wind around the lab room and some of the liquids could have evaporated off while we were measuring our values. These errors could be avoided by closing all the windows and preventing wind or other forces from altering the scales but evaporation is something we cannot control.


 * Teacher Comment: Mostly good. Awfully similar to several others I read. Make sure the report is not copied by others. 45/50 **