Chapman Cycle

In 1930s, Sydney Chapman resolved the chemistry process of ozone continually regenerated by converting ultraviolet radiation (UV) into heat in the Earth’s stratosphere is known as Chapman Cycle. It describes the four steps by which O2 is photolyzed to produce O atoms and O3, which can then be photolyzed to recover O2.

Chapman Cycle for Ozone Production:

Figure 1: Ozone formation

 Ozone formation:

2 atomic oxygen is formed by the dissociation of O2 by high energy ultraviolet photons

O2 + ℎν → 2O

Each oxygen atom then quickly combines with an oxygen molecule to form an ozone molecule

O + O2 → O3

The ozone-oxygen cycle:

Ozone strongly absorbs appropriate wavelength of UV radiation and is dissociated by these UV photons into O and O2

O3 + ℎν(240-310 nm) → O2 + O

The atomic oxygen produced quickly reacts with another oxygen molecule to reform ozone

O + O2 → O3 + excess kinetic energy

Ozone Loss:

The ozone is in stable balanced by the reaction of ozone and free oxygen atoms

O3 + O· → 2 O2

 

Resources:

NASA. (June 2000)’Studying Earth’s Environment From Space’ Retrieved on 6 March, 2015 from  http://www.ccpo.odu.edu/SEES/index.html.

Unknown (2010) ‘ Ozone Layer’ Retrieved on 11 March, 2015 from  https://www.ec.gc.ca/ozone/default.asp?lang=En&n=DB5CBDE6-1

Unknown (n.d.) ‘Ozone-oxygen cycle’ Retrieved on 6 March, 2015 from http://en.wikipedia.org/wiki/Ozone-oxygen_cycle

Ozone Layer

The atmosphere of the Earth is divided into five layers. From the closest and thickest to farthest and thinnest layer: Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.

The ozone layer refers to a region of Earth’s stratosphere that absorbs most of the Sun’s UV radiation. It was discovered by the French physicists Charles Fabry and Henri Buisson in 1913. The ozone can be measured in Dobson unit (DU) by using a simple spectrophotometer (the Dobsonmeter). It could be used to measure stratospheric ozone from the ground that was developed by the British meteorologist G. M. B. Dobson who explored the ozone properties.

Ozone is an allotropic form of oxygen which contains high concentrations of ozone (O3) relative to other parts of the atmosphere, although it is still very small relative to other gases in the stratosphere. It is a highly reactive gas which reduces the amount of harmful UV radiation from reaching the Earth’s surface.

 

Resources:

Caroline Tran, Dan Chong , Anne Keith, Jordan Shively (n.d.) ‘Depletion of the Ozone Layer’ Retrieved on 15 March, 2015 from http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Case_Studies%3A_Kinetics/Depletion_of_the_Ozone_Layer

Freddy (n.d.) ‘Layers of the atmosphere’ Retrieved on 15 March, 2015 from http://clccharter.org/freddy1/weather/atmosphere/layers.html

Unknown (n.d.) ‘Ozone layer’ Retrieved on 15 March, 2015 from http://en.wikipedia.org/wiki/Ozone_layer

Unknown (2010) ‘ The Ozone Layer’ Retrieved on 15th February, 2015 from http://eschooltoday.com/ozone-depletion/where-is-the-ozone-layer.html

Group Discussion on UNIT 3 topics.

1. Understanding Earth’s Energy balance is essential to understading the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square meter (W/m2), but the energy leaving Earth’s surface averages 390(W/m2). Why isn’t earth cooling rapidly?

After our group discussion, we think that the reason behind this is because our earth’s core is also emitting heat itself. Moreover, there are still heat trapped within the atmosphere which is then later reflected back to Earth. Therefore, when the reflected heat comes back by green house gasses, the atmosphere becomes hotter than before instead of cooling down.

2. Do you think the statement made by the cartoon is justified? Explain.

No, it is definitely not true . First we need to know that the seasons we are experiencing are a result of the Earth’s tilted axis as it revolves around the sun so it doesn’t mean that during winter we can be less concern about global warming  instead the effects of global warming actually become more visible. for example the temperatures during winter.  Numbers have shown that over the past decades, the temperature during winter has significantly increase and this can be due to the effects of global warming as global warming is changing the weather patterns. Avery good example would be Lake Erie not freezing during the winter of 2006 for the very first time in history. This shows that global warming has resulted in warmer temperatures.

Even though there will be variation in the temperature, the overall trend of increasing temperature still exists. This means that the cold weather still occurs, but with an steady rise in temperature in the long run.

3. One of the first radar devices developed during the World War 2 used microwave radiation of a specific wave range that triggers the rotation of water molecules. Why was the design not successful?

This is due to the reason that Water molecule itself is a greenhouse gas. The water molecules present in the atmosphere will absorb the radiation. The radar device is hence ineffective.

The absorption of electromagnetic radiation by water actually depends on the state of the water.

The absorption in the gas phase occurs in three regions of the spectrum. Rotational transitions are responsible for absorption in the microwave and far-infrared, vibrational transitions in the mid-infrared and near-infrared. Electronic transitions occur in the vacuum ultraviolet regions.

Liquid water has no rotational spectrum but does absorb in the microwave region.

Given that water molecules absorbs the microwave radiation, it would be more effective if a higher energy radiation is used. e.g uv but it would in turn lead to undesirable environmental as well as health concerns.

4. Now that you have studied air quality( unit 1), stratospheric ozone depletion(unit2), and global warming( unit 3), which do you believe poses the most serious problem for you in the short run? in the long run?

Air Quality would poses serious problem in short run as it can cause poor health. The effects can be seen almost immediate as air can be measured and categorized. For example, the haze problem in Singapore that happened in 2013 is a very good example of the importance of air quality. When the PSI hit above 400 which is in  the hazardous zone, everyone’s health is put a stake. The picture below shows the seriousness of how air quality is vital. Hence, actions and management can be taken quickly.

After studying the three chapters, it is rather clear that global warming would poses serious problem in long run as the effects are not immediate as the impact is gradually increasing over the years. Some impacts from global warming can already be seen and that includes ice are melting worldwide at a faster rate and sea levels are gradually increasing. Effects that could happen in the century would probably be stronger hurricanes and storms and higher frequency of floods and drought.

As such, it can be seen that this problem of global warming has to solve as soon as possible as by delaying it will only result in increasing the cost of solving the problem in future.  We need to learn how to solve the problem together as a whole otherwise the consequences would be disastrous.

6 Feb – minutes

Location:  SPMS MAS atrium

Time: 1500

Duration of the meeting: 15mins

Team members who attended: ALL

Topics discussed: Ozone layer and sub categories to find out more information about.

Tasks to be done before the next meeting:  

Research on sub topics.

1. 03 cycle, equations involved and factors affecting the cycle (Amelia)

2. CFCs effects on 03 , Chemical equations involved.(Kean Hean)

3. Positive effects of the ozone layer( yuhui)

4.Negative Effects of the depletion of ozone ( Jia Hao)

5. Effects of  ozone depletion on Sg (YatYan)

6.Effects of ozone depletion on our lives( Phebe)

 

 

 

 

AY2014/15 Sem 2