Lab Report The Function and Importance of Surfactant

The Function and Importance of Surfactant: Lab Report

Introduction

The purpose of this lab report is to demonstrate the function and importance of surfactants using household products. Surfactants play an important role in the respiratory system, whereby they coat the alveoli walls of the lungs (National Library of Medicine - NLM, 2017). According to the NLM, the ability of surfactants to coat the alveoli walls is rooted in their surface tension reducing capabilities. Two experiments were performed - whereby the first experiment was to observe surface tension created when drops of water are dropped on a penny and determine why a penny could hold so many drops of water before it ran off. The second experiment was performed to observe whether surfactants indeed counteract the properties of water by lowering surface tension of water molecules, and whether the absence of a surfactant could have an effect on the respiratory system. This is more so the case given that as the NLM (2016) points out, the ability of surfactants to lower surface tension is largely dependent upon the concentration of the surfactant on the surface of the alveoli. Therefore, when the concentration of surfactants is low, it would diminish the pressure to inflate the alveoli at exhalation leading to breathing problems (National Library of Medicine, 2017).

Materials and Methods

Two experiments were carried out using household products to demonstrate the importance how surfactants work. The first experiment, which involved surface tension, was first carried out before the effects of surfactant could be explored. In this experiment, a penny was first washed, rinsed, and dried with a paper. A clean eyedropper was filled with tap water. The dry penny was placed on a flat surface, and individual drops of water dropped on the surface of the said penny until the water ran off the penny. The individual drops of water dropped on the penny before water could run off the penny were then counted and recorded.

In the second experiment on the effects of surfactant, a clean shallow dish was placed on a flat surface and whole milk poured on it until it completely covered the bottom of the said dish. Second, a couple drops of food coloring were added to the milk using an eyedropper. The solution was then observed for two minutes. After the given timeframe elapsed, the distance from the center of the food coloring to the edge of food coloring was measured in millimeters using a ruler. Thereafter, the rate of movement per minute was calculated to determine the rate in millimeters per minute.

In the above solution, a couple of drops of dishwashing liquid were added drop-wise from the center of the dish. Two minutes later, the milk and the food coloring were observed and the distance from the center of the food coloring to the edge of the said food coloring measured in millimeters. The rate of movement per minute was also calculated to determine the distance in millimeters per minute.

To control the possibility of the dishwashing liquid reacting with the milk and food coloring in the second part of the surfactant experiment, a control experiment was performed whereby food coloring was added to the dish of milk without adding the dishwashing liquid.

Results

In the first experiment, 37 drops of water were dropped on the penny before the water ran off from the said penny. When the first drop of water was dropped on the penny, it formed a dome shape. As more drops of water were dropped on the penny, they seemed to be attracting each other whereby they piled up forming an even larger dome.

In the second experiment, when the food coloring was added to the center of the milk, the food coloring was suspended on the surface of milk. After two minutes of observation, the suspended later of food coloring remained the same. The distance from the center of the food coloring was measured and it was found to be two millimeters. The 2 millimeters were then divided by 2 and the rate of movement in millimeters per minute was, thus, found to be 1mm/min. When the dishwashing liquid was added to the center of the food coloring, swirls of colors were observed whereby the milk moved outwards carrying the food coloring with it. After two minutes of observation, the milk and the food coloring mixed leaving a very thin layer of food coloring at the edge. In this case, the distance moved by the food coloring was higher than when the dishwashing liquid was not added. Essentially, the distance changed from 2mm in two minutes to 7 mm in the same timeframe. This equated to a rate of movement of 3.5mm/min. The percentage change in rate of movement was as follows:

(3.5mm/min-1mm/min)/100=0.025mm/min%

Discussion

In the first experiment on surface tension, it is worthwhile noting that more drops of water were dropped on the penny than would have been expected. This is more so the case given that the tiny water molecules of water attracted one another forming a dome shape. According to Water Science School (2019), the dome-shaped or spherical droplet that was formed by water could be attributed to surface tension. According to the authors, surface tension is formed owing to the cohesive nature of water molecules. Essentially, there were no other water molecules on the surface of the penny. Therefore, as more drops of water were dropped on the penny, they cohered directly with the other water droplets. This is more so the case given that as Nave (2016) points out, the water molecules on the surface tend to have no molecules neighboring them. For this reason, the said molecules would react with the neighboring water molecules, thus creating surface tension (Water Science School, 2019).

In the second experiment, the food coloring was slowly spread on the surface of the milk. When the dishwashing liquid was added, the food coloring spread at a faster rate compared to when the dishwashing liquid had not been added. The speed of the food coloring was affected by the dishwashing liquid given that the dishwashing liquid lowered the surface tension of milk by absorbing the food coloring. According to Water Science School (2019), the dishwashing liquid has a lower surface tension (as a consequence of disinfection). Therefore, it disrupted the walls of the food coloring by spreading on its cell wall.

The experiment above happens to relate to the effects and importance of surfactants. This is more so the case given that as the dishwashing liquid was added from the center of the food coloring, it affected the interaction between the food coloring and milk. In essence, before the dishwashing liquid was added, the food coloring had formed a thin layer on the surface of milk. Since milk acted as water, it essentially meant that its surface tension was higher than that of the food coloring, thus making the food coloring float on its surface. Therefore, as the dishwashing liquid was added, the surface tension of milk was lowered - breaking the thin layer of food coloring. This allowed the milk and food coloring to interact. In essence, the dishwashing liquid performed the same role as a surfactant, which was to lower surface tension.

Data obtained from the two experiments relates to the first hypothesis that a penny could hold many drops of water owing to the high surface tension of water. The data also relates to the second hypothesis that the dishwashing liquid counteracts the effects of surface tension. This is more so the case given that the dishwashing liquid was able to reduce the surface tension of milk and allowed it to interact with the food coloring.