lab report chemistry (need in 10 hours )

LABORATORY 3

Revised SPR 2017

Density of an Unknown Solid

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Lab 3 Density of an Unknown Solid

OBJECTIVE

Given an unknown solid you should be able to correctly calculate the density of that solid. You should be able to use density to solve problems involving mass and volume.

Pre-Lab Activities

1. Read Lab 3

2. Complete PhET Sims online Pre-Lab Activity.

Lab Activities

1. Find the Density of the Unknown Samples.

2. Your Lab Instructor will initial the Title Page of Your Lab to indicate that you have attended the lab, completed the required lab activities, cleaned your lab bench and all equipment used, and returned all lab equipment to its designated space. A Lab Report that is not initialed in the Checkout box may not be graded. It is at the discretion of your Lab Instructor.

INTRODUCTION TO DENSITY AND SPECIFIC GRAVITY

The experimental purpose of this lab is to determine the density of a solid. You will use the information you learned in lab 2 about accuracy, precision, and significant figures as measured in the laboratory to use error analysis to evaluate your data.

DEFINITIONS

Density is defined as mass per unit volume. Density is a fundamental property of matter.

It is necessary to state the conditions of pressure and temperature because density varies as these conditions change. This is particularly true in the case of gases.

Experimental Errors

We can classify errors in our experimental work into two categories. The first we will call systematic errors; the second we will call random errors. You will find a discussion of these errors on in Lab 2 of your lab manual.

Accuracy and Precision

Accuracy is the agreement between your measured value (for example; a measured mass) and the "true" or accepted value. Percent error measures the degree of accuracy of an experiment.

experimental value - accepted value

percent error = x 100 accepted value

Precision is a measure of how carefully a measurement is made. It is not related to accuracy. Precision is measured in terms of percent of uncertainty which will be defined in detail a little later on.

Lab 3 Density of an Unknown Solid Pre LAB Worksheet

Complete the following questions using PhET Sims

Adapted from density lesson plan by Patricia Loeblein

( http://phet.colorado.edu/en/contributions/view/3406) PhET Sims are online simulations. You need to download the Density Simulation.

PhET Simulations http://phet.colorado.edu/

(you can Google “phet Sims”)

Click on Play with Sims then choose Chemistry and

Density

Click on Run Now! To being the program

1. Calculating Density

Choose Same Mass and complete the following table.

To determine the volume of a buoyant block that floats you can hold it under the water.

IMPORTANT – Remember to use the Significant Figure rules you learned in Lab 2.

Same Mass

Block	Mass, kg	Volume, L	Density, kg/L	Density, g/mL
Blue	5.00 kg
Yellow	5.00 kg
Green	5.00 kg
Red	5.00 kg

2. Choose Same Volume and complete the following table

Same Volume

Block	Mass, kg	Volume, L	Density, kg/L	Density, g/mL
Blue
Yellow
Green
Red

3. Choose Same Density and complete the following table

Same Density

Block	Mass, kg	Volume, L	Density, kg/L	Density, g/mL
Blue
Yellow
Green
Red

4. Choose Mystery and complete the following table

Mystery

Block	Mass, kg	Volume, L	Density, kg/L	Density, g/mL
Blue
Yellow
Green
Red

5.

Click on show table to determine the identity of the mystery blocks.

Mystery

Block	Color	Identity of Block Material
A
B
C
D
E

Lab 3 Density Experimental Procedures

Important Guidelines

1. Follow all lab safety rules.

2. You must wear goggles or safety glasses at all times when you are in the lab.

3. You must bring your own goggles or safety glasses.

4. Your instructor must sign your procedure before you begin any lab work.

1. Find the density of the samples assigned to you by your Lab

Instructor.

a. You should record its identity.

b. Describe the appearance of the sample.

c. You are to determine the density of your sample using two different methods.

d. You need to write a procedure giving the steps you will follow to find the density of the sample for each method. The procedure should be written as numbered list and should be clear and easy to follow. A fellow student with no knowledge of density should be able to follow your procedure.

e. You may use any lab equipment that is visible in the classroom. You may also use the analytical balances.

f. Your lab instructor must initial your procedure before you do anything else. g. Once your procedure is initialed by your lab instructor you are to follow the

steps in your procedure to find the density of your sample.

h. Obtain the actual density of your sample from your Lab Instructor and find the percent error in your density calculation.

i. Use your procedure to determine the density of the second sample. You can choose which method to use.

Lab 3 Report Density

Title Page

Name

Date of Lab

CHECK OUT Lab Instructor’s Initials Your Lab Instructor will initial the Title Page of Your Lab to indicate that you have attended the lab, completed the required lab activities, cleaned your lab bench and all equipment used, and returned

all lab equipment to its designated space. A Lab Report that is not initialed in the Checkout box may not be graded. It is at the discretion of your Lab Instructor.

Please tear this page out of your lab manual and turn it as the title page of your lab report.

Lab 3 Report – 15 points

Title page

PhET SIMS Worksheet (3 points) Experimental Procedure (2 points)

must be signed by lab instructor

list of steps and safety precautions

Results and Calculations Page(s) ( 4 points)

· state your results with correct units and correct number of significant figures

· show all calculations used to determine your results

· compare your experimental results with accepted results (if available), calculate the percent error

· if your percent error is large, explain why your results differ from accepted results

· list potential sources of error (both systematic and random error)

· how might you improve the experiment in order to obtain results closer to the accepted result

Answer the following question using complete sentences. Write neatly and legibly or type your answers. Use a separate sheet of paper.

1. Density is a property of matter. Is density a physical or chemical property?

Is density an intensive or extensive property? (2 points)

2. You can express the density of an object in units of kg/L or in units of g/mL.

How is the density of an object in kg/L related to its density in g/mL? (2 points)

3. You are given a sample block of an unknown metal. The block displaces

3.24 mL of water and has a mass of 62.5429 g. What is the density of the unknown metal? What is the metal? Cite the source you use to answer this question. See the HCC Library Homepage for information on citing sources. ( http://www.howardcc.edu/services-support/academicsupport/Documents/Writingtheresearchpaper.pdf) (2 points).

4. Watch Bunsen burner safety video in preparation for next week’s lab.