Rate of Evaporation- Research Paper

Internal Assessment: Rate of Evaporation Ann George Mr. Frias/4th Period Wheeler High School Research Question How will changing the molar mass of alcohol affect the rate of evaporation, represented by the change in temperature over time, measured using a temperature probe? Research/Abstract Alcohol is an organic compound in which the hydroxyl functional group, OH, is bound to a carbon atom. Its carbon center should be saturated; it should have single bonds to three other atoms. The different types of alcohols are determined by the kinds of CH2 groups while the number of CH2 groups there are tells you the volume of the alcohol.

The acyclic alcohols are the most basic and one of the most important groups of alcohol. The general formula of acyclic alcohols is: CnH2n+1OH. There are different types of acyclic alcohols. The most commonly used form of acyclic alcohol is ethanol which is a clear, volatile, flammable liquid that boils at 78. 4?. It is used as an industrial solvent, car fuel, and as raw materials in the chemical industry. Ethanol is widely used as a solvent for human contact or consumption, including perfumes, flavorings, colorings, and medicines. Another type of acyclic acid is methanol, and it is also the simplest sort of alcohol.

It is a clear liquid that resembles ethanol is odor and properties, but it has a slightly lower boiling point of 64. 7?. Methanol is mainly used as a solvent, antifreeze, raw materials, fuel, or as a denaturant for ethanol. Unlike ethanol, methanol is extremely toxic since one sip of methanol can cause permanent blindness. Two other kinds of acyclic acid are propan-2-ol and butan-1-ol. Just like ethanol, these two types of alcohols can be produced by the fermentation process. Propan-2-ol is a colorless, flammable chemical compound with a strong odor.

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It is the simplest kind of secondary alcohol which occurs when an alcohol carbons is attached to two other carbons. Butan-1-ol is a primary alcohol with a four carbon structure. Butan-1-ol is part of the group of “fusel alcohols” which has more than two carbon atoms and is soluble in water. It is used as an artificial flavoring that is present in many types of food and beverages such as butter, cream, ice cream, and candy. Pentan-1-ol is a 5 carbon atom. It is a colorless liquid with an unpleasant aroma. This alcohol can be prepared by the fractional distillation of fusel oil.

Some uses for pentan-1-ol include being used as a solvent for coating CDs and DVDs, and it is also used as a replacement for gasoline. Each of these acyclic alcohols has a general formula as follows: ethanol is C2H5OH, methanol is CH3OH, propan-2-ol is C3H7OH, butan-1-ol is C4H9OH, and pentan-1-ol is C5H11OH. Evaporation is a type of vaporization that occurs only on the surface of a liquid. For molecules of a liquid to evaporate, they must be located near the surface, be moving in the proper direction, and have sufficient kinetic energy to overcome the liquid phase intermolecular forces.

Since the kinetic energy of a molecule is proportional to its temperature, evaporation occurs more quickly at higher temperatures. As the faster moving molecules escape, the remaining molecules have a lower average kinetic energy, so the temperature of the liquid decreases. Also, evaporation tends to occur more quickly on liquids with higher vapor pressure. Alcohol evaporates faster than water because water has extensive hydrogen bonding between its molecules which results in its high boiling point whereas in alcohol, amount of hydrogen bonding is smaller as compared to water.

This makes the boiling point of alcohol less than water. A major factor that tells the rate of evaporation is the intermolecular forces between the molecules. The stronger the forces’ keeping the molecules in a liquid state, the more energy needs to escape. Other factors that affect the rate of evaporation include the concentration in the air since air that has a high concentration of the substance will evaporate more slowly. Surface also plays an important part in the evaporation process because substances with a larger surface area will evaporate faster, as there are more surface molecules that are able to escape.

Denser objects take longer to evaporate as well. The pressure of an object also effects evaporation since evaporation happens faster if there is less exertion on the surface keeping the molecules from launching themselves. The formula to determine the evaporation rate of a substance is as follows. Change in Temperature Change in Time Rate of Evaporation= In measuring the evaporation rate of a liquid, a temperature probe is most commonly used to calculate the decrease in temperature. If the evaporation rate occurs quickly, the temperature will also decrease quickly.

Hypothesis For determine the rate of evaporation of a substance, the change in temperature is divided by the change in time. Among the five previously mentioned alcohols, methanol, ethanol, propan-2-ol, butan-1-ol, and pentan-1-ol, the rate of evaporation for the methanol will be faster. Methanol will evaporate more quickly because its intermolecular forces are the smallest since it has the lowest relative molecular mass. This shows that the molecules in methanol can easily evaporate.

The butan-1-ol will evaporate the slowest because it has the highest molecular mass of all the alcohols given, so it therefore has the greatest intermolecular force of attraction. If the molecules’ properties are the same, then the intermolecular forces of attraction are proportional to the relative molecular mass. So as the molar mass increases, the rate of evaporation decreases. Materials/Safety * Safety goggles * 4 beakers, each one with a number from 1-4 * Methanol, ethanol, butan-1-ol, propan-2-ol poured into separate beakers * Pentan-1-ol * Xplorer GLX Pasco PasPort PS-2002 * Temperature probe

Procedure For this lab we were to find the rate of evaporation for the five types of alcohols mentioned from above. First we put on our safety goggles to protect our eyes from the aforementioned alcohols since they could cause irritation in our eyes. Next we set up our Xplorer GLX PasPort PS-2002 to graph. After that, we dipped the tip of our temperature probe into the first beaker of alcohol until the graph flat lined. Once that occurred, we removed the temperature probe from the alcohol and held it above the beaker until the graph on the Xplorer GLX Pasco PasPort PS-2002 started to decline, ndicating that the liquid was cooling off since it was evaporating. This process was repeated for the remaining alcohols. Finally, the temperature change of the alcohols was divided by the time it took for the temperature change, so we could calculate the rate of evaporation for the alcohols to figure out the identity of the alcohols. Data Table/Observations | Change in Temperature| Change in Time| Rate of Evaporation| Type of Alcohol| Liquid 1| 7. 1? | -18. 5| -. 384| Methanol| Liquid 2| 2. 9? | -51| -. 059| Propan-2-ol| Liquid 3| 1. 1? | -64| -. 712| Butan-1-ol| Liquid 4| 5. 9? | -65| -. 0908| Ethanol| Liquid 5 (mystery)| 2. 4? | -34. 5| -. 0696| Pentan-1-ol| Figure 1: This figure represents the data that was collected throughout the experiment. For each of the five liquids, we determined the change in temperature, the change in time, the rate of evaporation, and finally using all the data that we has gathered we determined the type of alcohol that the liquids were. When we received the different beakers with different types of alcohols, the alcohols all looked same since they are all colorless liquids.

We found the change in temperature was the part of the graph from when the graph flat lined at the top to when the line went down and just starts to come up. This part of the graph is the temperature change because when the temperature line begins to decrease, it indicates that the liquid is evaporating. We knew that the liquid was evaporating since when evaporation occurs, the molecules change into a gaseous state therefore absorbing heat. When the molecules absorb the heat, it cools down the surrounding environments temperature.

Evaporation was complete when we noticed the temperature start to increase again on the graph. The temperature increase indicated that the area from where the liquid had evaporated was starting to get back to the room’s temperature. We also found the time it took for the temperature to change so that we could figure out the evaporation rate for each of the liquids. Results/Analysis The results of the experiment are as follows. Liquid 1 had an evaporation rate of -. 384, liquid 2 had an evaporation rate of -. 059, liquid 3 had an vaporation rate of -. 0172, liquid 4 had an evaporation rate of -. 0908, and liquid 5 had an evaporation rate of -. 0696. Once we determined the evaporation rate, we used that to figure out the identity of each type of liquid. The higher the evaporation rate was, the lower the molecular mass was for each of the alcohols. There were instances throughout the experiment were possible errors could have occurred. One such instance is when we took the temperature probes out of the liquids, so that the liquid would evaporate.

If we took out more liquid on one of the liquids then it would have taken longer for that liquid to evaporate than the others. Also if we waved the temperature probe in the air, then the liquid might have evaporated faster than it was supposed to. Another factor that affects the evaporation rate is if fresh air is moving over the substance all the time, then the concentration of the substance in the air is less likely to go up with time, thus encouraging faster evaporation. Conclusions

Our conclusions were right because as seen from our results, as the molar mass decreased the rate of evaporation for the substance increased. This is because more energy escapes if the forces that are keeping the molecules together in a liquid state are stronger. This also represents that the evaporation rate of a liquid is inversely proportional to the molecular masses of the substances. Even though this does not full represent the relationship between the evaporation rate and the number of carbon chains that are in the alcohols, it supports the fact that they are inversely proportional.

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