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Details in attachments

For this experiment, begin by reading the Introduction and Procedure. Use the procedure to follow along with the video to record your data and observations. Along with the video, there are also images where you will find your specific sample information. Find the images attached. That is your marbles sample. Everyone will use the same image of the empty beaker on the balance to be used for the weighing by difference calculation. Once you have calculated your sample’s density, post the density into the discussion board. You will then use other classmates’ density results to complete the analyses. Please do not wait until the last minute as you and your classmates are dependent on each other to complete this experiment. Be considerate. Assignments due for this module are the Data Collection and Results Pages, Post-lab Assignment, and Quiz.

TASKS

1. Material to use:

a. Attached pdf for experiment details.

b. Video: https://www.youtube.com/watch?v=U91wuaK4OZA&list=PL_rbtfnB-4sCP7i7uRBDX56KR6FU1pnug

c. attached images

2. Complete the “Data and Results Page”

3. Complete the “Post_Lab Assignment”

Experiment 4: DENSITY

Data Collection and Results Pages Name: (Show work for all calculations.) Date:

I. Density of Water

Room Temp:

Correct Density of Water at this Temp:

Reference:

Calculate the density of water for each trial:

Trial 1: Trial 2:

Calculate the Average Density of Water: Note: The average value cannot have more precision than the individual values. As a rule of thumb, the average should have the same decimal places as the individual values.

Calculate the Error in the Average Density: (Watch your sign and sig. fig.!)

Calculate the % Error in the Average Density: (Watch your sign and sig. fig.!)

1

2 EXPERIMENT 4: DENSITY

8 mL Trial

10 mL Trial

Mass of Water in Cylinder

Volume of Water in Cylinder

Calculated Density of water

Average Density of Water

Correct Density of Water

Error in the Average Density

% Error in the Average Density

II. Density of Marbles

Mass of the 3 marbles = Volume of the 3 marbles = Density of the 3 marbles* =

*Show calculation for the density of the 3 marbles:

Calculate the Average Density from the class data:

Calculate the Error in the Average Density:

Calculate for % Error in the Average Density:

2

EXPERIMENT 4: DENSITY 3

CLASS DATA ON DENSITY OF MARBLES

Name of Student

DENSITY OF MARBLES

reported

Yours

1.

2.

3.

Average Density

Correct Density (from instructor)

Error in Average Density

% Error in Average Density

3

Experiment 4:

Density

1

Purpose: You are to learn the proper way to report the mass and volume of various

samples, and make use of the information to determine the density.

Introduction:

Density is one of the physical properties of matter that helps us identify it. The density of a

sample is defined as the mass per unit volume of the sample. It is the ratio of its mass to its

volume and can be calculated by the equation

volume theis V and mass theis M density, theis D where

V

M

D =

Consider a large rock and a small pebble. The large rock is most likely to be heavier than

the small pebble, but it is not necessarily denser. In order to compare their densities the two

objects would have to be the same size, or you could compare their ratios of mass to volume.

In determining the density of a liquid, you will need the volume and mass of a sample of the

liquid. It would not matter how much of the sample you use as long as it does not exceed

the capacity of the apparatus you are using, and that the volume and mass are obtained for

the same source. Density is said to be an intensive property because it is independent of the

sample size. In contrast, mass and volume are said to be extensive properties because they

are dependent of the sample size.

In this experiment you will determine the density of water, using 8 mL and 10 mL. The

densities of the two samples are to be determined to see whether the difference in volume

would affect the density.

Some of you may recall from past experience that the density for water it is 1.00 g/mL. In

actuality, that value is only an approximation, as it will vary depending on the temperature.

Your instructor will look up the “correct” density from a handbook.

The volume of a liquid is measured using a graduated cylinder. Water has a curved surface

called a meniscus. The proper way to measure the volume is to read the bottom of the

meniscus at eye-level as shown in Figure 4.3. This is easier said than done with water being

colorless. For this reason you will prepare a Reflection Card to make the bottom of the

meniscus more visible.

2 EXPERIMENT 4: DENSITY

2

Figure 4.3

The mass is measured with an electronic balance. Obviously you cannot pour the liquid

directly on the balance pan. It is to be obtained by the method of “weighing by

difference”. The following example illustrates how density is calculated using this

technique:

A student weighed a 50-mL beaker. He then pipetted 10.00 mL of a liquid substance

into the beaker and weighed it again. The difference in masses was the mass of the

liquid that was pipetted.

Mass beaker + liquid 42.3220 g

Mass beaker (-)30.0830 g

Mass liquid 12.2390 g

Volume liquid pipetted 10.00 mL

The density was calculated:

density = = 1.224 g/mL

Procedure

(Using a pen or pencil, record by hand all of your data and results on the Data Collection

and Results Pages.)

Part I: Density of Water

1. Your instructor will either announce on the board or show you how to determine the

room temperature and known density of water at that temperature. Record these in

your lab notebook.

2. Record the mass of a clean and dry 10-mL graduated cylinder and use this mass in

your calculations for both trials. You should use the same balance throughout this

part of the experiment.

Always remember to read the

meniscus at eye-level.

Reflection card

EXPERIMENT 4: DENSITY 3

3

3. Add approximately 8 mL of deionized water to the grad cylinder. Wipe the outside

of the grad cylinder totally dry and record the total mass of the grad cylinder and the

water.

4. Calculate the mass of water in the 10-mL grad cylinder.

5. Read and record the volume of the water to the correct significant figures with the

use of the Reflection Card. (Hold the card behind the grad cylinder with the black

line just slightly below the bottom of the meniscus. The black line will reflect off the

bottom surface and make it more visible.) It is essential that you take time to figure

out how many decimal places you should be recording.

6. Empty the grad cylinder. (You need not dry it. Just shake out the excess water.)

7. Repeat Steps 4 through 6 using approximately 10 mL instead of 8 mL of deionized

water.

8. Complete the calculations specified on the Data Collection and Results Pages.

Part II: Density of Marbles

In this section you will learn to determine the volume of solids by the application of

Archimedes’ Principle, which states that an object is buoyed up with a force equal to the

weight of the liquid it displaces. This principle is often applied to the measurement of

the volume of a solid. Simply put, the volume of an object is equal to the volume of

water it displaces if it is denser than water (and therefore does not float on the surface of

the water).

Procedure:

Determination of the Mass (by the method of weighing by difference)

1. Obtain 3 marbles from your instructor.

2. Weigh a 50-mL beaker and record the mass in your lab notebook.

3. Gently place the 3 marbles into the beaker and record the mass again. (Remember to

use the same balance.)

4. Take the beaker and marbles to your bench. Hold on to your 3 marbles. You

MUST use the same 3 marbles in the next section.

5. Calculate the total mass of the 3 marbles.

Determination of the Volume of the Marbles (using Archimedes’ Principle)

6. Place exactly 30.0 mL of water in your 50-mL graduated cylinder and record the

volume to the correct sig. fig.

7. Carefully slide your 3 marbles into the graduated cylinder, taking care that no water

splashes out of it and record the volume again.

8. The difference between the two volume readings you recorded is the volume of

water displaced by the marbles. According to Archimedes’ Principle, this is the

volume of the marbles. Calculate and record the total volume of the 3 marbles.

4 EXPERIMENT 4: DENSITY

4

Determination of the Density

9. Remembering the relationship between density, mass, and volume, calculate the

density of your 3 marbles and record it on the Data Collection and Results Page.

Watch your sig. fig. at each step of your calculations.

10. Obtain the density from 3 other students, record their full names and the densities

they obtained. Compare the values you and your fellow students obtained. Are there

any that look totally unreasonable?

11. Calculate the average density of the marbles that you and other students obtained and

record it on the Data Collection and Results Pages.

12. Obtain the correct density of the marbles from your instructor and calculate the error

and percent error of the average density of the marbles. Watch your sig. fig. and sign

(whether positive or negative).

Units of Volume and Density of a Solid

The volume of liquids is generally measured in mL; whereas, that of solids

is generally recorded in cm3. Since 1 mL is exactly 1 cm3, the numerical

value is unchanged. Record the volume of the marbles as cm3, and the

density as g/cm3.

Name __________________________

Module 4

Post-Lab Assignment

Short Answer (30 points)

Answer the following questions based on material covered in this module. (5 points each)

(You must use complete sentences when answering each question.

1-point deduction per question not answered in complete sentences.)

1) The two trials involved different volumes of water. Are your two densities significantly different? Is this as you expected? Why or why not? Explain.

2) Do you think the density of a liquid would increase or decrease when the temperature goes up? Explain.

3) Do you and your classmates’ marbles results have good precision? Explain.

4) Do you and your classmates’ marbles results have good accuracy? Explain.

5) Using the average density, calculate the mass of 8 marbles, which has a total volume of 16.0 cm3. Show your calculation setup carefully, including units. (Hint: First give the equation that relates density with mass and volume of a sample.)

6) Explain fully why Archimedes’ Principle would not apply for finding the volume of a cork (such as a cork taken from a bottle of wine).

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