Finding Density Using Graphing Techniques



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Honors Chemistry

Finding Density of Water Using Graphing Techniques

SHOW ALL YOUR WORK INCLUDING DATA TABLE ON GRAPH PAPER!

INTRODUCTION:

The density of a substance is defined as the mass divided by the volume: d = m / v. Using graphing techniques, a plot of mass vs. volume will yield a slope (Δy/Δx) of density.

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Y = m X

In this experiment, you will find the mass of water for five different volumes and plot them. Using a line of best fit, the slope will give you the value of density for water.

MATERIALS (2 People / Group):

Graduated cylinder, Triple Beam Balance, Beral Pipet, Tap water, Salt Water Solution

PROCEDURE:

1. Make a data table onto the graph paper which will record all the data you collect in the lab.

2. Find the mass of an empty, dry 10mL graduated cylinder. Using the triple beam balance estimate the mass to the nearest 0.1 gram.

3. Add exactly 1.0mL of water to the cylinder. Remember, the bottom of the meniscus should just be touching the 1.0mL line.

4. Find the mass of the cylinder and 1.0mL of water to the nearest 0.01gram. Record on the data table.

5. Repeat with 2.0, 3.0, 4.0, and 5.0mL of water.

6. Repeat the above procedure using the salt water solution provided in class.

ANALYSIS:

1. On graph paper, construct a graph of your data. Mass on the vertical axis, and volume on the horizontal axis. Plot both sets of data, fresh water and salt water on the same graph.

2. You will draw best fit lines; a straight line that comes closest to connecting all of your data points. You line may not touch some or all your data points: that is okay.

3. Make sure you title your graph, label both axis, and lines (salt and fresh water) and with the units.

4. Pick two points actually on your line to calculate slope. Remember: slope equals change in Y/ change in X. Include the units of your slope.

5. The ACTUAL VALUE of density of fresh water is approximately 1.0 g/mL and the density of salt water is about 1.1 g/mL. Find both percent errors:

Percent Error: |Actual Value – Experimental Value| x 100%

Actual Value

Pre-Lab:

1) Active Reading on Page 1 – Materials, Procedure, and Analysis – Highlight / Underline

2) On your graph paper, draw TWO different tables – One for Fresh Water, One for Salted Water

Density for Fresh Water /Salted Water

|0 |1 |2 |3 |4 |5 | |Mass of Cylinder + Water (g) | | | | | | | |Mass of water only (g) | | | | | | | |Volume of water (ml) | | | | | | | |

3) Prepare the following graph (just draw one graph) on the graph paper following the ANALYSIS steps 1-3:

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Post-Lab:

1) Plot the graph (two lines on the same graph using different colors of pens)

2) Find the Experimental Value of density:

Density = mass = ∆ mass = slope = ∆Y = (Y1-Y2) =

Volume ∆ volume ∆X (X1 -X2)

3) Find the Percent Error:

Percent Error: |Actual Value – Experimental Value| x 100% =

Actual Value

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Key:

Density for Fresh Water

Density for Salted Water

Title:

Mass of Water Only (g)

After Experiment:

You will draw the lines of Best Fit for both Fresh Water and Salted Water

Volume of Water (mL)

These values must be on the line of best fit

g/mL

Experimental Value

Do this for both Fresh Water and Salted Water ( You should come up with One Experimental Value for Each Water

On page one on the bottom

X-Axis Label (With Unit)

+ve % error

Take Absolute Value

Do this for both Fresh Water and Salted Water ( You should come up with One Percent Error for Each Water

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