Short (one page) essays
Summary
You will most likely be required to write short essays in Chemistry and Biochemistry, and possibly other units also. Short essays are often one part of a larger assignment comprising several different tasks. It is important to know that short essays do NOT follow the standard academic essay format (they do not have an introduction and conclusion).
This section has three short (one page) essays which all answer the same question. Two of the short essays received a High Distinction grade (9/10) and the other received a Fail grade (3/10). Each answer has the marker's comments at the end; so you can see what constitutes a good short essay answer, what is unacceptable, and WHY.
Samples of short (one page) essays in The Sciences
The question
Write a one page essay describing some chemical process in which the kinetics are of importance to the situation in which the process is occurring. Cite the resources you have used in gaining information for your essay. You need to make explicit mention of the chemical reaction(s) involved and how the kinetics of the reaction(s) are of significance.
Sample short essay 1: 9/10
A common kinetic reaction that is relevant, especially to university students, is how alcohol is broken down in the liver. It is an important reaction for drivers to be able to judge as it tells them whether they are sober enough to legally drive.
In this reaction the liver breaks down 90% of the alcohol consumed into the body. It is broken down by an enzyme called alcohol dehydrogenase which strips enzymes from the alcohol to form acetaldehyde. Aldehyde dehydrogenase (another enzyme) converts the acetaldehyde in the presence of O2 to acetic acid. The acetic acids are then used to form fatty acids or further broken into CO2 or H2O.
CH3CH2OH CH3COOH → CO2 + H2O Enzyme
The kinetics in this reaction are extremely important because of the variability caused by catalysts and other factors concerned with the body. These include:
- the greater the concentration of alcohol the faster it absorbs into the body
- carbonated beverages tend to speed up the rate of absorption
- if the stomach is full then the rate of absorption will be slowed down
- people who drink more frequently have a better ability to break down alcohol more quickly because their liver is better adapted
- having a large body size means that less alcohol has to be broken down for you to be under the limit
- women tend to have a smaller body size, so are more likely to have to spend more time to break down alcohol.
All of these kinetic factors influence the rate at which alcohol is absorbed into the body and therefore will affect the rate at which alcohol can be broken down in the liver and also affect how much time it will take until you are legally able to drive home.
All of these kinetics are important to consider when dealing with this reaction because the difference between alcohol types and physical factors makes the rate of reaction very variable.
Responsible Services of Alcohol Manual
This essay goes into considerable detail about the different factors involved in the kinetics of the chemical reaction, and relates chemical kinetics in a real way to everyday life. It shows a thorough understanding of the issues. Referencing is very limited, but in this context of a short essay as part of a much bigger group of assignment tasks, referencing was not of major concern. In most other contexts, though, this lack of referencing technique would result in lost marks.
Sample short essay 2: 9/10
Kotz & Treichel (1999, p. 1) state that chemical kinetics is "the study of the rates of chemical reactions under various conditions and of reaction mechanisms". Knowing how fast a reaction will go or how to manipulate its speed by "outside" forces is very important to many chemical industries, including the military.
An important chemical reaction in naval hardware is the production of O2(g) from the decomposition of concentrate H2O2, known as HTP (BBC 2001).
2H2O2(l) O2(g) + 2H2O(vap) catalyst
The O2 from this is used to allow engines to burn fuel while in the water, specifically those in submarine torpedoes, for example the Russian SS-N-16 (BBC, 2001). Being able to control how fast this reaction occurs is a major safety concern.
The reaction works by allowing the H2O2 to come into contact with certain metals to decompose to water vapour and oxygen; without the metal the H2O2 does not react (Kotz & Treichel, 1991). The speed of the reaction depends on the metal present. For example, the reaction is relatively slow in the presence of nickle, fast in the presence of copper and extremely fast and violent in the presence of brass (Piarault-Roy et al., 2002). Brass is very common on board naval vessels due to its low corrosion properties. So, it is important for those involved to know how to control the rate of reaction in the torpedo to prevent the torpedo from either stalling (too little oxygen) or exploding (too much oxygen), both of which are hazardous to the submarine and crew. For example, the Russian submarine Kursk, was downed when a torpedo leaked H2O2, which reacted with the brass fitting, causing it to explode and setting off a chain reaction in the warheads of the forward torpedo room (BBC, 2001). In this example, chemical kinetics plays an important role.
References
- BBC (2001, updated May 2002). Horizon special: What sank the Kursk? Science and Nature. Retrieved from www.bbc.co.uk/science/horizon/2000/kursk.shtml
- Kotz, J.L. & Treichel, P. (1999), Chemistry & Chemical Reactivity, (4th ed.). Fortworth, TX.: Saunders College Publishing.
- Pirault-Roy, L., Kappenstein, C., Guerin, M., Eloridi, R., & Pillet, N. (2002). Hydrogen Peroxide decomposition on various supported catalysts effects of stabilisers. Journal of Propulsion and Power, 18, (6), pp. 1235-1241. Retrieved from http://pdf.aiaa.org/jaPreview/Jpp/2002/PVJAIMP6058.pdf
This essay uses an interesting example and relates the chemical kinetics of the relevant reaction very thoroughly. Shows good connections made between chemistry and real-life issues and concerns. Referencing is according to the APA style.
Sample short essay 3: 3/10
Chemical kinetics is the study of rates of chemical reactions which are under different conditions, and includes reaction mechanisms. Kinetics take place either at the macroscopic level or the particulate level. One important chemical process is photosynthesis, which has the following chemical equation:
6CO2 + 12 H2O + light energy → C6H12O6 + 6O2 + 6H2O
Plants utilise CO2 and light and turn it into sugar to be used later for growth.
Source: Campbell (1999) Biology 5th edition
This essay does not say anything about the kinetics of the chemical reaction, so does not really answer the question. It is incomplete and does not demonstrate adequate understanding of the subject matter. Inadequate research and referencing.