Johannes Christian A. Santos
Christian R. Santos
De La Salle University-Dasmariñas
Dasmariñas, Cavite Philippines
The densities of several liquid and solid samples were determined as an exercise in measurement. Density, being an inherent and intensive property of a substance, was also used to determine the identity of an unknown liquid sample. Proper procedures on measurement were observed in order to determine the mass, volume, and density of the samples. Four liquid samples were used namely water, isopropyl alcohol, coconut oil, and an unknown liquid sample. The experimental density values were measured at 1.01 g/ml, 0.800 g/ml, 0.940 g/ml, and 0.800 g/ml respectively. The range of percentage error was below 5.00% for all the samples. The unknown liquid was identified as kerosene by comparing the measured density with its theoretical value. For the solid samples a wood block, a marble, and pebbles were used. The experimental density values were measured at 0.500 g/cm3, 1.99 g/cm3, and 2.61 g/cm3 respectively. The over-all success of the experiment was hinged on the accuracy of measuring the needed quantities and the mentioned results attested that such success was achieved.
Measurement is the process of determining an unknown quantity by comparing it to a known standard. Such process would require proper observations of needed procedures in order to ascertain the accuracy and integrity of the measured quantities. In this experiment, the densities of several solid and liquid samples were determined as an exercise in measurement. Density is the measure of compactness of a substance which is mathematically expressed as the ratio of mass with volume. Density is an inherent property of pure substance, which means that it is constant at a specific temperature. It is also an intensive property, which means that it does not vary with the amount of the substance at hand. It is therefore useful in determining the identity of an unknown substance (1).
MATERIALS AND METHODS
In the first part of the experiment, the density of water, isopropyl alcohol, coconut oil and an unknown liquid were determined. An empty dry graduated cylinder was used to measure the volume of 50 ml of water and 5.00 ml of the other liquid samples. The mass of the samples was measured using a triple beam balance. The experimental density values were calculated and respectively compared to the theoretical values in order to compute the percentage error.
In the second part of the experiment, the density of a wood block, a marble, and pebbles were determined. The mass of the samples was measured using a triple beam balance. A ruler was used in measuring the length, width, and height of the wood block. Meanwhile, the radius of the marble was calculated from its circumference which was measured by winding a piece of string around it and measuring the equivalent value in centimeter. Lastly, the volume of the pebbles was determined by displacement method (2).
RESULTS AND DISCUSSION
Four liquid samples were used in the experiment namely water, isopropyl alcohol, coconut oil, and an unknown liquid sample and the summary of their density determination is listed in Table 1 below. The experimental density values were measured at 1.01 g/ml, 0.800 g/ml, 0.940 g/ml, and 0.800 g/ml respectively. The range of percentage error was below 5.00% for all the samples which means that the results were highly accurate. The unknown liquid was also identified as kerosene by comparing the measured density with its theoretical density.
Table 1. Densities of Liquid Samples
| |Water |Isopropyl |Coconut Oil |Unknown Liquid | | | |Alcohol | | | |Mass of dry, empty cylinder (g) |95.1...
References: (1) Brown, T.L..; Lemay, H.E.; Bursten, B.E.; Murphy, C.J. Chemistry: The Central Science. 11th Edition. 2008. Prentice Hall. USA.
(2) Figueroa, L. and Samonte.J. Laboratory Manual in General Chemistry. 3rd Edition. 2010. C&E Publishing. Philippines.
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