Physical Science (PHSC 100) Virtual Lab Expt. #3: Density and Specific

Gravity

Name: ________________________ Section: _______ Date: ______

Note on this virtual Lab Experiment

Read the introductory principle, procedure and experimental materials outlined below, and understand as to how this virtual experiment would be conducted under real lab condition to generate the theoretical data supplied in Tables below. After clearly understanding the procedure and the formula for the calculations, enter calculated values in the blank columns and write brief discussions as per the guideline, and Submit it back in the Drop Box.

Introduction

Density

Density is a physical property of solids and fluids that can be defined as the mass (m) or quantity of a substance contained in one unit of its volume (v).

The density of water is 1.0 g/ml (1g/cm³); in other words 10ml has a mass of 10g.

Specific Gravity

Specific gravity of a body is that number which denotes the ratio of the mass of a body and the mass of equal volume water.

Specific gravity = Mass of solid or liquid

Mass of an equal volume of water

Water is used as the standard, because the density of water does not vary by more than ¹/₂ of a percent over the temperature range of zero to 30-degree Celsius.

The density and specific gravity of any substance are numerically the same when the density is expressed in g/ml. When density is expressed in g/ml (g/cm³), specific gravity can be calculated by dividing the density value by 1 g/ml (1g/cm³), thus making it unit-less. Example, for copper: density is 8.5 g/ml (g/cm³); specific gravity is 8.5.

Standard specific gravities (densities) values of some materials are shown below:

Water1.0 (1g/cm³)Aluminum 2.7 (2.7g/cm³) Copper 8.5 (8.5g/cm³) Steel7.8 (7.8g/cm³)

The main objective of this experiment is to determine the densities and specific gravities of different materials and compare them with their standard values.

Materials and Procedure

Equipment

• Beakers Graduated cylinders
• Analytical Balance Metal pieces (small)
• Metal roundsOverflow-cup with nozzle

Experimental Procedure

Density of water

• A 100ml graduate cylinder is filled with water more than half and read the exact volume in ml is read to one decimal place, and record in Table 1, under the column designated volume of water (ml), Rep #1, third column.
• A 150ml beaker is tared (zero) on analytical balance.
• The volume of water in the cylinder is transferred quantitatively into the beaker; mass in grams of water in the beaker is measured, and data record under mass of water (g), in the second column, Rep #1
• The same procedure is repeated for Rep #2 and #3, the mass and volume data recorded in the appropriate columns.

Assignment

The theoretical data generated for mass and volume of water are already given in Table 1. From these data, calculate the density and % error values in the blank last column:

• The density of water (d) is calculated by dividing the mass (m) in grams of water to the volume (v) of water in ml.
• The mean density values are calculated by adding the three replications and dividing by 3. The error % as compared to the standard density of water, which is 1g/ml, is calculated using the following formula.

% Error = */Standard value – observed mean/ x 100

Standard value

*absolute difference (no negative sign)

Density of pieces of metal (copper)

• Some metal pieces (copper) provided are weighed on a balance (about 60g) and the exact weight in gram recorded in Table 2, under mass (g) in column 2, Rep #1.
• A 100-ml cylinder is filled to about 50 ml of water and exact volume in ml is recorded under the V₁ column, Rep #1.
• The weighed metal pieces are immersed into the water in the cylinder.
• The new volume of water in ml is recorded under the V₂ column in the data Table, which is the volume after immersing the metal pieces.
• The change in volume of water (V₂ - V₁) is calculated and recorded (This is the actual volume in ml of the metal pieces).
• This procedure is repeated in the same manner to complete Rep #2 and #3.

Assignment

The theoretical data generated following the procedure outlined above are given in Table 2. From these data, calculate the density and % error values and enter in the last column blank spaces.

• Density of metal pieces is calculated by dividing mass of metal by change in volume, (g/ml)

• The mean density values are calculated by adding the three replications and dividing by 3. The error % as compared to the standard density of copper, which is 8.5g/ml, is calculated using the formula given under density of water measurement.

Density of metal rounds (steel)

• The mass in gram of three metal round (steel) provided is measured one at a time and data entered in Table 3, under column 2, Replications #1, #2, #3, respectively.
• Overflow-cup with a drain-nozzle is placed on a bench above the water sink and filled with water until excess water flows out through the nozzle and levels off.
• After the excess water stops dripping out of the overflow-cup, an empty beaker is held under the nozzle with one hand and the metal round, of which mass entered in Rep #1, is gently dropped in the water with the other hand; the metal will displace a fraction of the water and water flows out through the nozzle into the beaker.
• The content of the beaker is then poured into a small graduated cylinder, and the volume is measured in ml and data recorded under volume of metal column.
• The experiment described for Rep #1 is repeated in the same manner for metal rounds 2, and 3, and data entered in Row 2 and 3, in the appropriate columns.

Assignment

The theoretical data generated following the above outlined procedure are given Table 3. From the given data, calculate and enter the density for each replication, the mean density value, and the % error of the experiment, using the given formulae.

• The density (g/ml) of the metal is calculated for each replication by dividing the mass of metal round (g) by the volume of metal (ml), and results entered in the last column.
• The mean density values are calculated by adding the three replications and dividing by 3. The error % as compared to the standard density of steel, which is 7.8g/ml, is calculated using the formula given under density of water measurement.

DATA SHEET

Table 1. Density of water

Table 2. Density of pieces of metal

Table 3. Density of round metal (steel)

Discussion

In the space provided below, briefly discuss the results of each of your experiments by indicating the mean and percent error values. Also indicate the level of precision of the experiment, by comparing the measurement results in the different replications, as well as the level of accuracy of the experiment by comparing the means with their respective standard values. Try to give explanation for the level of error obtained by indicating possible sources of error, if high % error (>10%) is observed.

1. 1. Density of water

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1. 2. Density of metal pieces

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1. 3. Density of metal rounds

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