The Influence of the Nature of a Liquid on its Rate of Evaporation - Research Paper Example

 The Influence of the Nature of a Liquid on its Rate of Evaporation. Introduction: Rate of evaporation of a liquid depends on many factors. Nature of a liquid may be one of the most important factors which determine its rate of evaporation. In this experiment we will test the hypothesis that different liquids have different rates of evaporation even when other factors of influence remain constant. This can happen since liquids are made up of different molecules, different in the amount of attraction that exists between them. The rate of evaporation also depends on the surface area and the temperature of the liquid (Deese, 2009). Therefore, an experiment of examining the influence of surface area can be done using the containers with different radii. Another experiment to examine the impact of temperature can be carried out by exposing the liquid to evaporation in different temperatures. Experimental Design Plan: Let us consider three liquids, namely, Acetone, Benzene and Chloroform for our experiment which we test if have different degrees of volatility. We take three identical clean and dry measuring flasks Fa, Fb and Fc. We pipette out 20 ml each of the liquids acetone, benzene and chloroform respectively to these measuring flasks. We take care, in exposing the liquids to the external environment as little as possible, by immediately closing the lids as we pipette out the liquids. We weigh each of the measuring flasks and note down the initial weights, in kg, Wa, Wb and Wc. we now place the three measuring flasks in a constant lab temperature zone and simultaneously open the lids from the three measuring flasks and start the stop clock too. Here in the set up, the nature of the liquid, which we assumed to have the influence on the rate of evaporation of a liquid, is the independent variable. By using the identical measuring flasks and the lab temperature, we have kept the variables, surface area, temperature and time controlled. According to our hypothesis, the rate of evaporation is the dependent variable. After 30 minutes, close the lids of the three measuring flasks simultaneously, measure the final weights of the three measuring flasks and note down the weights as Wa1, Wb1 and Wc1. Now having taken down the initial and final weights, calculate the difference between them, the amount of liquid evaporated in 30 minutes, (Wa-Wa1), (Wb-Wb1) and (Wc-Wc1), in kg. Divide the difference by time period, 1800 s, to obtain the rate of evaporation of the three liquids. S. No. Liquid in the measuring flask Initial weight (kg) Final weight (kg) Rate of evaporation, r, (kg/s) 1 Acetone Wa Wa1 (Wa-Wa1)/1800 2 Benzene Wb Wb1 (Wb-Wb1)/1800 3 Chloroform Wc Wc1 (Wc-Wc1)/1800 Blank template for the collection of data. S. No. Liquid in the measuring flask Initial weight (kg) Final weight (kg) Rate of evaporation, r, (kg/s) 1 Acetone 2 Benzene 3 Chloroform After calculations we find that ra < rb < rc. That implies that the three liquids have different rates of evaporation, in the order, acetone < benzene < chloroform. Scientific Report. Evaporation is an important natural phenomenon. It is an integral part of water cycle, which again is, a pivotal part of the balance in nature. In this context, it is of the reasonable interest to investigate the factors which affect the rate of evaporation. Finding out the rate of evaporation of a liquid also helps in determining the health concerns and fire hazards associated with that liquid. Though, there are exceptions, volatility is predominately the property of liquids. We observe this phenomenon of evaporation of liquids almost everywhere around us. From rain water on lands and roads vanishing to the nail polish solidifying, we witness numerous examples of the phenomenon just through our bare senses. But we recognize that all these evaporations do not occur in the same speed. That makes us to presume that there must be certain factors which influence the rate of evaporation of a liquid. Though environmental factors such as temperature, surface area, and pressure may influence the rate of evaporation, we feel, under certain observations, that even another factor may influence it too. The difference between the rates of evaporation acetone in nail polish and that of water in a similar bottle seems significant, as all the other environmental factors will almost be the same. This leads to the hypothesis that the nature of liquid may be a decisive factor in determining its rate of evaporation. Because of this, different liquids may have different rates of evaporation. Experimentation and Data Collection Having hypothecated that the nature of a liquid influences its rate of evaporation, we move forward to experimenting and testing the claim. We consider three volatile liquids, acetone, benzene and chloroform to test the hypothesis. The idea behind considering this three much volatile liquids, is to ascertain if there is a major difference, which is supposed to be small, in their rates of evaporation. We take some amount of all the three liquids, here 20 ml, in a small measuring flask. We weigh the three measuring flasks after filling them with the liquids acetone, benzene and chloroform and closing the lid. We use an accurate electronic balance for weighing and note down the weights. All the units used will be those of the S.I. system throughout the experiment. Measuring the weights of the liquids with the measuring flasks is the first of date collection in the experiment. Let the initial weights be Wa, Wb and Wc respectively. The next step would be to expose the liquids to environment for the process of evaporation. We simultaneously open all the lids from the measuring flasks and let the liquids evaporate for a certain amount of time. The procedure of allowing all the liquids to evaporate together in the lab environment helps to keep the environmental differences that may be present at bay and is time saving. After certain time of evaporation, we again simultaneously close the lids and measure the final weights in an electronic balance and take down the weights. A good number of measures can be taken to ensure the quality of data collected. The measuring flasks should be clean and dry and can be labeled as Fa, Fb and Fc for the three liquids acetone, benzene and chloroform respectively for ease of recognition. The lids should be closed as soon as after filling the liquids. A fine and accurate electronic balance helps to measure the initial and final weights to the desired degree. The simultaneity of opening and closing the lids of the three measuring flasks before and after exposing the liquids to evaporation is the crucial step in ensuring the quality of the data collected. Results: After the data collection the difference between the initial and final weights of the liquids gives the amounts of liquids evaporated during the considered time period. The rates of evaporation of a particular liquid are calculated as the ratio of its amount evaporated to the time period. The results clearly show a significant difference in the rates of evaporations of acetone, benzene and chloroform. Chloroform stands out among the three as the most volatile liquid with the highest rate of evaporation among the three. Benzene comes second in the order, and acetone, the least evaporative among the three. This confirms our hypothesis that different liquids have different rates of evaporation. The nature of liquid is a major influencing factor in its rate of evaporation. The following plot illustrates the evaporation of the three liquids in the time period of 30 minutes. The top curve is for acetone, middle for benzene and the bottom, for chloroform. ^Remaining liquid in the measuring flask Time  This result that the nature of liquid determines its rate of evaporation is an accepted one with a sound theory in its support. The reason behind is well explained by the kinetic theory. Every molecule in a liquid has a particular amount of kinetic energy. This energy will not be uniform through out the liquid. The molecules in a liquid are held together by a force of attraction like van der Waal’s force. The molecules which acquire the energy enough to overcome these forces of attraction escape to the vapor state. Evaporation causes cooling. One good example is when you put a little amount of a volatile liquid like acetone on your body, it gives a cooling effect. The molecules of acetone absorb the heat energy of the body to give the cooling effect. The heat energy is then converted to the kinetic energy required for the molecules of acetone to escape to vapor state. The molecules in different liquids are held together by forces of different kind and degree of energy. Hence these different molecules require different amounts of kinetic energy to for escaping to the vapor state. Hence there exists the difference in the rates of evaporation of different liquids. The liquids under study are more volatile, especially compared to water. Water has a comparatively strong hydrogen and ionic bonding between its molecules, making them a bit difficult to escape to vapor state easily. Conclusion: In this experiment though, some minor mismanagements in some cases, like closing the lids simultaneously, can just skew a result bit. But it is almost negligible to our final conclusion that different liquids have different rates of evaporation. In other words, nature of a liquid determines its rate of evaporation. The experiments can be carried out to find out how the other factors like surface area, temperature affect the rate of evaporation. The same experiment can also be conducted with a different set of liquids other then acetone, benzene and chloroform for instance. Clearly, any set of liquids gives the same result: the nature of a liquid plays a significant role in its rate of evaporation. Reference: 1. Deese, W. C. (2009). "Evaporation," Microsoft® Encarta® Online Encyclopedia, Retrieved June 23, 2009 from http://encarta.msn.com. Read More