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Hello. I am from Singapore.

Application Exercise: Session 4, Global Climate Change

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Application Exercise 4

  1. Majority of the energy leaving the earth’s surface does not go directly out to space.  The emitted energy is absorbed by clouds and by the gases in the atmosphere again.  Some of it gets redistributed by convection. Energy is also absorbed by the greenhouse gases such as methane, nitrous oxide, ozone, carbon dioxide and water vapor.  These gases constantly emit the sun’s energy back into the atmosphere and keep the earth a habitable temperature. The energy that doesn’t make its way out is responsible for global warming, which results in Earth not cooling rapidly.  
  2. The statement suggests that the occurrence of winter is an indication of reduced impact of global warming. This statement is incorrect. There may be certain regions of the Earth at certain period of time experiencing winter, however, this does not mean that the Earth is getting colder or the average temperature of Earth is getting lower.  The occurrence of winter is just a change in season and has nothing to do with reduced impact of global warming.  It is noted that global warming is the increase of Earth’s average surface temperature due to effect of greenhouse gases. Greenhouse gases are the primary cause of global warming. The occurrence of winter does not change the fact that there is still high concentration of greenhouse gases in Earth. To reduce the impact of global warming, we should instead reduce the emission of greenhouse gases. This can be done by planting more trees and reduced combustion of fossil fuel.
  3. Microwave radiation induces rotational energy in its surrounding molecules. If a radar send out a large amount of radiation of this wavelength the molecules in the air, water and other surrounding objects would gain so much energy that they would start to emit heat. This heat could increase the temperature in a lake with a few degrees, making it hard for certain species to survive in this new environment. The surrounding air would also increase in temperature which may not be very suitable with the very popular topic global warming.
  4. In the short run, air quality is the most problematic. This is because the negative impacts of air quality is felt directly. Poor air quality severely affects the quality of life as the it causes direct respiratory problems, allergies and negatively affect the state of living. On the other hand, the impacts of ozone depletion and global warming is not felt directly hence, in the short run, air quality is the most serious problem. In the long run, global warming is the most important issue. While air quality affects the quality of life, it does not threaten life itself. Global warming in contrast, affect the life around the earth. The resulting altered climate, rising sea levels, melting of polar ice caps etc sabotages the livelihood of animals. Arguably, if this continues, the livelihood of human beings may be threatened as well. This is observed where low lying islands are being submerged by the sea due to rising sea levels. While ozone depletion may result in threatening of humans livelihood, it is not as severe. This is because it is easier to reduce substances that harms ozone then to reduce greenhouse gases. For example, the effort to reduce CFCs in the atmosphere has seen great success while many countries still struggle to control their emissions, due to conflicting economic interests.

Answers for Application Exercise Session 3: Energy from Combustion

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Qn 1. a) The burning of charcoal briquettes is an exothermic process. This because I went camping once and lit a fire surrounded by some rocks and sand. But some dry grass caught fire and it amplified quickly before it could be extinguished. Thus, it does not need additional energy to amplify and a lot of heat is released in the process.


          b) The evaporation of water from your skin in an endothermic process. This because once I forgot a bucket of water outside in the sun, and after a while the amount of water decreased. The water molecules gains energy from the environment and can therefore evaporate.


          c) The melting of ice is an endothermic reaction as well. This because if you place ice cubes in a glass of water they will melt. The melting speed depends on how warm the surrounded water is. This because the ice cubes gain energy from the surrounding which make them melt.

 

Qn2) Exothermic reactions are chemical reactions with releases energy. In order for this, the total energy of the reactants must be higher than that of the final products, in other words, the energy absorbed for breaking of bonds in the reactants must be less than the energy produced for the forming of bonds for the products. As such, the bond strength of the reactants needs to be lower than that of the products. For a good explosion to happen, a high enthalpy is needed for the release of large amount of energy.  Hence, the greater the difference between the bond strength of the reactants and products, the better the explosion.

 

Qn3. Temperature is the measurement of a heat source whereas heat is the energy found in that source. Heat can be transferred from a source to another source whereas temperature cannot be transferred. For example, when boiling water, the heat energy causes the water to boil; i.e. steaming and bubbling water under heat, whereas the temperature shows that the water is boiling at 100°C.

 

Qn 4. a) Gasoline with an octane rating of 98 has a high resistance to cause engine knock. Engine knock occurs when the fuel mixture ignites too early. High octane Gasoline burns slower and at a higher efficiency, thus it is more resistant to knock.

b) Oxygenates are added to motor vehicle fuels to make them burn more cleanly, thereby reducing toxic tailpipe pollution, particularly carbon monoxide. Oxygenates are favored not only for their vehicle emission benefits but also their blending properties in motor gasoline. Thus, with the gasoline at a high octane rating, it is probable that it contains oxygenates.