The purpose of this lab is to calculate density. Density is the ratio of a substance's mass to its volume. Density is an intrinsic or characteristic property of matter in that any given amount of the same pure or homogeneous substance will have the same density. Other characteristic properties include solubility, conductivity, and malleability. Density is also known as a physical property in that it can be measured without changing the substance. This is opposed to a chemical property, for example flammability or reactivity, which do change the substance.

As a characteristic physical property, density can be used to identify an unknown sample of a pure substance. There are many ways to calculate density including a hydrometer, a spring scale, a pan balance or through volumetric displacement using a graduated cylinder. Archimedes of Syracuse is credited with having discovered the volumetric displacement method for determining density when he had to determine whether a temple offering had been made of pure gold or of some alloy (Vitruvius 2010). The equation for density is:

 

                                         ρ      =      m                                      (1)

                                                         v

 

In Eq. 1, and using SI units, density, symbolized by the Greek letter Rho, ρ, is mass, m, in kilograms (kg) divided by volume, v, in cubic meters (m³). Since pressure and temperature affects density, measurements should be carried out at Standard Temperature and Pressure (STP) (273.15 K and 100.00 kPA). For example, at STP, one 1.00 m³ of Cu has a mass of 8.94 kg and hence has a density of 8.94 kg/m³. 

Experimental error can be calculated using Eq. 2: 

 

% error = |experimental value - theoretical value| . 100 

                                                             theoretical value            (2) 

 

In Eq 2, experimental error would be the absolute value of measured density (kg/m³) as found in the experiment subtracted from the theoretical density (kg/m³) value as shown in the periodic table divided the theoretical density (kg/m³) and multiplied by 100 in order to have a percentage.

That means, if the experimental density of Cu was found to be 8.71 kg/m³, then the experimental error would be:

2.57 % error = |8.71 - 8.94| . 100 

                                                                     8.94

It was hypothesized that samples of Al, Cu and Sn could identified after their densities had been determined through volumetric displacement in a solvent and the resulting values compared to a table of known densities.

 

MATERIALS 

• samples of Al, Cu and Sn
• 3, 100 mL graduated cylinders
• distilled water
• Mettler Toledo PM4600 digital balance

 

PROCEDURE 

INCLUDE PROCEDURE AND INSERT IT HERE.

RESULTS 

Table 1: Measurements
Unknown	Mass (g)	Volume-Initial (mL)	Volume-Final (mL)
Unknown 1
Unknown 2
Unknown 3

 

ANALYSIS 

The volume of each unknown was calculated by subtracting the initial volume of water in each graduated cylinder from the final volume of water in each graduated cylinder after the unknowns were added (Table 2). The density of each unknown was calculated using Eq. 1. For example, for unknown 1, the calculation was: 

 

SHOW WORK FOR UNKNOWN 1

 

The same process was repeated for unknowns 2, and 3 and the densities of all 3 unknowns were recorded (Table 2). 

 

Table 2: Densities of unknown metallic solids.
Unknown	Volume (mL)	Mass (g)	Density (g/mL)
1
2
3

 

Experimental densities were then compared to standard densities for the 10 listed unknowns from the Merck Index and the identities of the unknowns proposed (Table III). Error was calculated using Eq. 2: 

For example, for unknown 1, the calculation was: 

SHOW WORK FOR UNKNOWN 1

The same process was repeated for unknowns 2, 3, and the percentage errors were recorded (Table 3). 

 

Table 3: Proposed identities of unknowns and percentage error.
Unknown	Proposed  Identity	Experimental Density (g/mL)	Standard Density (g/mL)	Error (%)
1
2
3

 

DISCUSSION 

Unknown 1 was ANSWER. Unknown 2 was ANSWER. Unknown 3 was ANSWER. The experimental results had a percentage of error between LOW VALUE and HIGH VALUE. Although there were many potential sources of error, the reproducibility of the digital balance and the accuracy of the graduated cylinders should be examined. The Mettler Toledo PM4600 digital balance has a reproducibility of +/1 VALUE. The 100 mL Class A graduate cylinder has an accuracy of +/- VALUE. It is thought that the reproducibility of the measurements on the digital balance and the accuracy of the glassware WOULD OR WOULD NOT have an effect on the identification of the unknowns. The reason why is __________. 

 

CONCLUSIONS:

Through the volumetric displacement method of calculating density, it was determined that unknowns 1, 2, and 3 were ____.

Use the following information for the next four numbers An entity set up a branch in a province. The entity and its branch provided the following data on the second year of branch's operation: Home Office Sales revenue to outside customerP1,000,000 Beginning inventory Purchases from outside supplier Shipment to branch Shipment from home office Ending inventory Operating expenses 50,000 400,000 200,000 c. P130,000 d. P123,000 80,000 150,000 the Branch The following additional data are provided: The home office to branch's mark-up based on cost last year is 80% of this year's mark-up on cost. 1/5 of the beginning inventory of the branch came from outside supplier. 24% of the ending inventory of the branch came from the last year's shipment from the home office while 50% of the ending inventory of the branch came from current year's shipment from the home office. P500,000 30,000 100,000 250,000 4. What is the ending inventory to be reported by the entity in its combined external statement of financial position? a. P128,000 b. P115,000 SUBJECT 6. What is the net income to be reported by the entity in its external combined income statement for the current year? a. P810,000 b. P857,000 c. P853,000 d. P864,000