Lab # 2: Identification of Three Metals by Density Determination

Background Information:

As we begin of exploration of chemistry we will be encountering many different substances. Each unique type of matter has its own set of properties associated with it. The type of properties of a substance can be categorized in a few ways. Many properties of a substance or element are called physical properties of matter. These types of properties can be observed without changing the identity of the substance. Some properties cannot be seen unless the substance is changed on the molecular level. These types of properties are called chemical properties.

Task 1: Think of a list of physical properties of matter. Create a second list of chemical properties. Together we will create two master class lists of physical and chemical properties. Place all of these lists in your lab notebook.

We can further categorize the physical properties of matter as either extensive properties or intensive properties. Those properties that fall into the category of intensive depend only upon the identity of the substance. That is to say any size sample of a particular substance will have these properties. Extensive physical properties depend upon a particular sample of a particular substance.

Task 2: In your lab notebook create a list of intensive and extensive properties.

One particular property we will examine and use today is that of density. We know density as the amount of mass per volume of an object. This is a ratio of mass to volume and can be thought of as a measure of how tightly packed the molecules in an object are.

Density = mass/volume

D = m/v

Materials: For each lab group

(1)  1 Quadruple beam balance

(2)  1 Ruler

(3)  3 metal cylinders of unknown identity

(4)  100ml graduated cylinder

(5)  A copy of Table S from the chemistry reference tables

Procedure:

Today we will use density to help us identify the type of metal each of the cylinders is made of. In order to do so you must measure the mass and volume of each object.

1.  Examine the three metal cylinders. Create a table with two columns, one labeled extrinsic properties and a second labeled intrinsic properties. Create three rows, one for each metal and list the properties in the appropriate column for each metal.

2.  Using the quadruple beam balance find the mass of each cylinder to the nearest tenth of a gram.

3.  Next measure the volume of each cylinder using the method of displacement. Please note that when you drop each cylinder into the graduate, DO IT AT AN ANGLE or you may crack or shatter the equipment.

4.  Also calculate the volume of each cylinder mathematically. Take the measurements using the ruler.

5.  Create a table titled Measured Mass and Volumes of 3 Metal Cylinders and create columns for all three measurements made. Place your data gathered here.

6.  Calculate the density of each of these metals. Please show your work. Create a new table titled Densities of 3 unknown metals. Name the metal cylinder by the color observed and record your densities to the nearest hundredth of g/cm3.

7.  Using Table S identify the element that each of the three cylinders is made of and justify your position.

Discussion:

As your write your lab report please keep in mind: the various types of properties, density and its formula, the ways in which we determined our measurements and calculations, the use of Table S and ways to potentially improve this experiment. We will discuss the format of the report in class on Friday. You must have your data tables with you at this time!