Surface
Surface Tension of Liquids
Karen Mae L. Fernan
Department of Chemistry, Xavier University-Ateneo de Cagayan, Philippines Date performed: Nov. 22, 2012 ∙ Date Submitted: January 16, 2013
E-mail: fernankarenmae26@yahoo.com
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Abstract
Surface tension is defined as the energy or work required to increase the surface area of a liquid due to intermolecular forces. Measuring the surface tension is useful in identifying unknown liquids and to check for its purity. By capillary method, the surface tension of a given unknown liquid was obtained. Water was used as reference liquid and both liquids were subjected to capillary method at 20, 30 and 40℃. The surface tension of water was used to calculate the radius of the capillary. The equation γ= 12ρgrh , where g is the acceleration due to gravity, r is the calculated radius of the capillary at a certain temperature, h is the capillary rise and ρ is the density of the liquid, was used to calculate for the surface tension of the unknown liquid. In the experiment, the calculated surface tension of the unknown liquid H was 22 dyne/cm at 20℃ , 22 dyne/cm at 30℃ and 18 dyne/cm at 40℃. It was found to be close to the surface tension value of isopropyl alcohol which is 21.7 dyne/cm at 20℃ with a percentage error of ±1.38%.
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RESULTS AND DISCUSSION Table 1: Height and density of water and unknown liquid at 20.0 ℃ | Water | Unknown Liquid | | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Average | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Average | Height (cm) | 6.3 | 6.3 | 6.3 | 6.4 | 6.3 | 2.4 | 2.4 | 2.4 | 2.4 | 2.4 | Density (g/mL) | 0.998203 | 0.794 | Table 2: Height and density of water and unknown liquid at 30.0 ℃
Karen Mae L. Fernan
Department of Chemistry, Xavier University-Ateneo de Cagayan, Philippines Date performed: Nov. 22, 2012 ∙ Date Submitted: January 16, 2013
E-mail: fernankarenmae26@yahoo.com
-------------------------------------------------------------------------------------------------------------------------------
Abstract
Surface tension is defined as the energy or work required to increase the surface area of a liquid due to intermolecular forces. Measuring the surface tension is useful in identifying unknown liquids and to check for its purity. By capillary method, the surface tension of a given unknown liquid was obtained. Water was used as reference liquid and both liquids were subjected to capillary method at 20, 30 and 40℃. The surface tension of water was used to calculate the radius of the capillary. The equation γ= 12ρgrh , where g is the acceleration due to gravity, r is the calculated radius of the capillary at a certain temperature, h is the capillary rise and ρ is the density of the liquid, was used to calculate for the surface tension of the unknown liquid. In the experiment, the calculated surface tension of the unknown liquid H was 22 dyne/cm at 20℃ , 22 dyne/cm at 30℃ and 18 dyne/cm at 40℃. It was found to be close to the surface tension value of isopropyl alcohol which is 21.7 dyne/cm at 20℃ with a percentage error of ±1.38%.
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RESULTS AND DISCUSSION Table 1: Height and density of water and unknown liquid at 20.0 ℃ | Water | Unknown Liquid | | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Average | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Average | Height (cm) | 6.3 | 6.3 | 6.3 | 6.4 | 6.3 | 2.4 | 2.4 | 2.4 | 2.4 | 2.4 | Density (g/mL) | 0.998203 | 0.794 | Table 2: Height and density of water and unknown liquid at 30.0 ℃
References: 1 Surface Tension. Capillary Action. Page 5 of 9. http://scipp.ucsc.edu/~haber/ph5B/bubble.pdf (Date accessed: January 07, 2013) 2 Surface Tension of Liquids. http://www.udel.edu/pchem/C446/Experiments/exp1.pdf (Date accessed: January 08, 2013) 4 How does capillary rise vary with diameter? http://answers.tutordynamic.com/7630/how-does-capillary-rise-vary-with-diameter-of-the-capillary (Date accessed: January 08, 2013) APPENDICES * Equation 1 : to calculate for surface tension of water γ= (-0.15996)*(t℃) +75.96 = (-0.15996)*(20℃) + 75.96 = 73 dyne/cm