chem lab 1.docx

Group 5 Susan Yu, Angela Liu, Jonathan Zhang

Lab - Density of Solids

Purpose: To compare the densities of three different solids and designate density as either an intensive or extensive property

Hypothesis: If we were to compare the densities of three different solids, then we will observe density to be an intensive property.

Materials: Metric cm ruler 250mL Graduated Cylinder Balance Scale 3 different solids Aluminum pellets Calculator

Procedure: The first step in our experimental procedure was to find the volumes of all the objects. For the rectangular prism, a metric ruler was used to measure the dimensions and then the volume was computed with a calculator. For irregularly shaped objects which could not be measured with a ruler, displacement was used in a 250 mL graduated cylinder by filling it up with a random amount of water, placing the object in, and then recording the differences in the two volumes. To find mass, an electronic balance scale was used. Before every measurement, the scale was zeroed. With the respective volumes and masses, density was calculated.

Data:ObjectVolume () Mass ()Density ()% Error

7Comment by Angela Liu: Our Group Data starts here1643.542.70

966.950172.472.57614.6

211335.602.70

ALP413.79310

1Comment by Angela Liu: Michelle N's Group Data starts here25.600171.796.7105150

1611.424104.319.1308240

182464.902.70

ALP1.23.182.70

16Comment by Angela Liu: Lizi X's Group Data starts here4.011.412.97.4

136201.655.6110

1875163.902.219

ALP50102.73230

Calculations:Comment by Susan Yu: Jonathan, we need to include the other two groups calculations too and then if we get different answers we need to change on the data table.DONT FORGET PERCENT ERRORComment by Jonathan Zhang: alright alright now i think ill write them all outFormulas for calculations:

Analysis Questions:

1. Graph the relationship (best fit line) between mass and volume for the 12 samples.

2. Describe and discuss trends in your graph.

Over all 12 samples, the mass generally increased as the mass increased. This is reasonable when compared to the formula for density. Density is a ratio of mass over volume, and for any substance, the density is always the same regardless of how much matter is present. Therefore, as one variable, either mass or volume changes, the other must respond with a similar change to maintain the constant density ratio.

3. Is density an intensive or extensive property? Explain your answer.

Density is an intensive property, meaning that the density does not depend on the amount of matter present. The density of any substance will be the same, no matter how large or small the substance is. Density is a ratio of mass over volume, which both change in similar motion and proportionately. When the mass of a substance increases, its volume will inherently increase as well, and given that both samples are in the same state of matter, the density will thus remain the same.

4. You have 2 cubes, A and B, that are the exact same size. The only thing that is different about them is their densities. Cube A has a density of 1.44g/cm^3 and Cube B has a density of 2.37g/cm^3. How is it possible that the blocks have different densities even though they are the exact same size?

The reason the blocks have different densities even though they are the same size is because their masses are different. Density depends on two things, mass and volume. In this case, the volume is a constant through both cubes, and thus the differentiating factor must be the masses of the cubes. Cube B has a higher mass than Cube A.

5. List 4 intensive properties. List 4 extensive properties.

Four intensive properties are color, odor, melting point, and density. Four extensive properties are mass, volume, length, and area.

6. Solids typically have a higher density than their liquid form. Water is an exception to this, Explain why.

Ice is less dense than water because as water cools down, hydrogen bonds form between adjacent water molecules, forming a crystalline like structure which results in a greater space between individual molecules in solid form, making ice less dense than its liquid state, water.

7. Two different lab groups found the density of the exact same solid cube, using a metric ruler and a pan balance. Group 1 measures the dimensions of the cube with proper precision, while Group 2 measures one decimal point short. Both obtain the proper mass in thousandths from the pan balance. How will their data compare once calculations are performed? Assuming that Group 1s data is accurate, what will the percent error for group 2 be if their measurement of the edge of the cube is 0.5 cm less? Use hypothetical data to show the comparison and write a few sentences elucidating the comparison of the outcomes of the two groups.

If we have a situation where Group 1 measures the edge of the cube to be 1.5cm, then Group 2 will have incorrectly measured 1.0cm. Assuming that the mass is 11.111g/cm^3, Group 1 will achieve a density of 0.30 g/cm^3, and group 2 will derive a density of 0.09 g/cm^3. Percent Error:

Using these hypothetical measurements, it is clear that Group 2 will be far less accurate with their answer, and if the experiment were to entail minute measurements, the percent error would be even higher.

Conclusion: The purpose of this experiment was to classify density as either an intensive or extensive property. Through this experiment, we applied the analysis of the density formula, and after analysis, it was concluded that density is an intensive property, meaning that it is not dependent on the amount of matter present when measuring. This finding supported and agreed with our hypothesis. All of the samples we analyzed in this experiment were all of the same substance, aluminium, which has a density of 2.7g/cm^3. Our group measured 4 aluminium items and we derived a density of 2.7g/cm^3, 2.5671g/cm^3, 2.7 g/cm^3, and 3 g/cm^3, with a 0%, 4.6%, 0%, and 10% error respectively. Additional data from other lab groups was collected and calculated, yielding densities of 6.7105 g/cm^3, 9.1308 g/cm^3, 2.7 g/cm^3, 2.7g/cm^3, 2.9 g/cm^3, 5.6g/cm^3, 2.2g/cm^3, and 2g/cm^3. Through these results, we have discovered that density is an intensive property, as even with varying masses and volumes of the same substance, the derived density was for the most part near the true 2.7 g/cm^3 of aluminium. Observable in the calculated densities are very large densities, some of which have over 90% error. Given that all the samples were of aluminium, it does not make sense that such numbers should show up, and such numbers may have been caused by the incorrect reading of the graduated cylinder used to measure volume. This experiment entailed using the graduated cylinder for measuring volume using displacement, and had the graduated cylinder not been properly read at the meniscus or worse in the wrong units, outlier measurements would have appeared. Given the precision of the electronic balance, its measurements were satisfactory, however due to the lack of small capacity graduated cylinders, larger ones were used to measure volume, which did not provide accurate data, so for further investigation, small capacity graduated cylinders should be used to improve precision.