# Density Experiment

**Purpose**

The objective of this experiment is to study one of the physical chemistry properties of given objects and identify their chemical identities.

**Tools and supplies:**

Pennies(Three rolls)

Measuring cup (with small base and graduated in mL)

**Theory**:

Density is defined as mass per unit volume and it is one of the physical properties of the matter that can lead to identification of a chemical element.

To determine the density of a substance, the mass of a certain amount of the substance is determined and divided by its volume. In the basic metric system of units, mass is measured in kg and the volume is determined in m3 leading to the unit of “kg/m3”. Very often smaller units of the metric system of units are used to specify the density in the “g/cm3” (grams per centimeter cubed).

**Procedure**:

Fill the measuring cup with water to its half-full mark. Drop 20 pennies in the cup and record the water level in the following table. Add another 20 pennies and record the position of the water level in the table. Continue adding pennies, 20 at a time, and record the water level in each case until you have a total of 300 pennies in the cup.

The values entered in the second row of the table following “V” are the actual readings on the measuring cup as the pennies are added. Values entered in the last row following “ΔV” are found by subtracting the value of

“V” for “0” pennies from the content of second row.

**Analysis**

Enter the number of pennies in the column “A” of excel spreadsheet in the cells “A1” to “A16”. Knowing that the mass of a penny is 2.5 grams, enter the mass of the pennies of column “A” in the “B” column (highlight B1-B16 and type =A1*2.5 , hold the control key and hit the “enter” key). Enter the corresponding values for ΔV in column “C” of the spreadsheet. Plot the content of column “C” as a function of the content of column “B”, use a linear trendline and find the equation of the line. to do so, highlight the cells B1-B16 and C1-C16 by placing the mouse cursor in the cell B1 and drag to C16 while holding the mouse button down. Click on “Insert” of the menu bar and then click on the “Scatter” in the charts panel of the ribbon and pick “Scatter”. Once the data points are plotted, right-click on one of the data points and pick the linear trendline and check the box to “Display Equation of Chart”. The equation displayed on the chart should be in the following form with “a” and “b” being some numbers: y = a x + b . The value of “a” in front of “x” represents the density of the pennies in the unit of “g/cm3”. Search the “web” to determine the chemical element whose density matches (or comes close to) the value of “a” from your graph and identify the element from which pennies are made.

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