CHEM115 LAB 1 DENSITY

pdf

School

Rivier University *

*We aren’t endorsed by this school

Course

101

Subject

Chemistry

Date

Dec 6, 2023

Type

pdf

Pages

Uploaded by briannayoung024

Brianna Krzyminski CHEM115 Lab 1 TITLE : Density Determination: Quantitative Measurement BACKGROUND INFORMATION : The study of chemistry involves not only observing, but also measuring. Careful attention should be given to the degree of uncertainty in your measurements. Record only those digits which are significant and use only those digits in your calculations. The accuracy of your methods can be reported with your results in terms of percent of error. The percent error in calculations and measurements is a comparison of differences between experimental results and theoretical values, expressed as a percentage. Percentage error can be determined as follows: % error = experimental value – theoretical value X 100 theoretical value A useful way of comparing two substances is to compare their densities. By carefully measuring the mass and volume of two substances, their densities can be calculated as follows: Density = Mass/Volume OBJECTIVES : In this experiment, you will *Determine the density of different substances *Calculate the percentage error in your results EQUIPMENT : 10 ml graduated cylinder 50 ml graduated cylinder Test tube brush PROCEDURE : 1.) Prepare a data table as directed in the analysis. A. Density of an unknown Liquid . 1.) Measure the Mass of a 10 ml graduated cylinder. 2.) Pour approximately 9 ml of the liquid into the graduated cylinder. Record, to the nearest .01 ml, the exact amount of liquid you use. 3.) Measure and record the mass of the graduated cylinder and the liquid. B. Density of solids . 1.) Obtain two different metals, measure and record their masses. 2.) Put about 25 ml of water into the 50 ml graduated cylinder. Accurately read the volume of water you use, and record. 3.) Carefully immerse one metal into the water in the graduated cylinder. Carefully read the new volume and record. 4.) Repeat steps 2&3 with the other metal.

ANALYSIS : 1.) Prepare a data table to record your observations. Follow the sample format for your table. Calculate the density for the unknown liquid, and the metals. Mass Calculation: 48.1925 g – 39.8673 g = 8.3252 g Density Calculation: 8.3252 g = 0.888 g/mL 9.38 mL Volume Calculation: 67.0 mL – 73.4 mL = 6.4 mL Density Calculation: 57.9824 g = 9.1 g/mL 6.4 mL Volume Calculation: 96.8 mL – 75.6 mL = 21.2 mL Density Calculation: 57.9747 g = 9.1 g/mL 21.2 mL 2.) Once you have completed your measurements, use your chemistry book to determine the unknown metals true density. True Density Mineral Oil : 0.89 g/mL True Density Metal #1 (Copper Cu) : 8.96 g/mL True Density Metal #2 (Aluminum Al) : 2.7 g/mL QUESTIONS : 1.) Calculate the percentage error for the unknown liquid, and two metals. Use significant digits and show set-ups for your calculations. % error = | true density - experimental value | X 100 true density Material Mass Volume Density Graduated Cylinder 39.8673 g Graduated Cylinder & Liquid 48.1925 g Liquid (Mineral Oil) 8.3252 g 9.38 mL 0.888 g/mL Material Mass Volume Density Water 67.0 mL Water & Solid #1 73.4 mL Solid #1 (Copper Cu) 57.9824 g 6.4 mL 9.1 g/mL Material Mass Volume Density Water 75.6 mL Water & Solid #2 96.8 mL Solid #2 (Aluminum Al) 57.9747 g 21.2 mL 2.73 g/mL

Mineral Oil : | 0.89 - 0.888 | x 100 = 0.22 % 0.89 Copper (Cu) : | 9.1 - 8.96 | x 100 = 1.6 % 8.96 Aluminum (Al) : | 2.73 - 2.7 | x 100 = 1.1 % 2.7 2.) What were at least two likely sources of error? Two of the most likely sources of error are related to human error and/or equipment error. Values recorded off the graduated cylinders to obtain volumes weren’t likely to be perfectly accurate due to volumes falling between measurement lines and having to guesstimate the exact volume. Equipment error could be a variable when considering the possibility of the scales utilized to obtain mass not being perfectly calibrated. 3.) The method used to find the densities of the metals will not work for all solids. Why not? Suggest a method of determining the density of these solids. Water displacement was utilized to determine volumes in this experiment. Water displacement may not be appropriate for finding the volumes of other objects due to the type of material and or shape / size and the ability to accommodate those variables while still remaining accurate. A pycnometer is another means to calculate density that could be utilized in these types of scenarios. 4.) Water is often used as a standard in making comparisons between densities of substances. Based on your data of waters density, suggest a reason for using water as a standard. Water is a great standard to use because it has a true density of 1 g/mL, additionally water is an extremely abundant/available substance. 5.) Is density an intensive or extensive physical property? Explain why density can be used to determine the identity of an unknown substance. Density is an intensive physical property. The values used to find density (volume / mass) however, are extensive because they can vary / change depending on sample size. The calculation of density utilizing those values however should not change; this property of density is what makes it a great way to determine the identity of an unknown substance as it is a constant. The story of Archimedes and the gold crown is a great example for why/how density can be used to identify an unknown substance.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version