greenhouse lab.doc - Greenhouse Gases Background notes for...

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Greenhouse Gases Background notes for Teacher: Radiation from the sun reaches the Earth. Some of this radiation is absorbed by the Earth and warms it up naturally making the earth similar to a greenhouse. Without this greenhouse effect life on earth would not be possible our average temperature would be below freezing. Daily temperature fluxuations would be great enough to create severe weather patterns due to the extreme hot to cold changes nightly. An equilibrium is reached where the amount of radiation coming in is matched by the radiation escaping from the atmosphere, resulting in a fairly stable temperature and climate. Anthropogenic (man-made) emissions are changing the composition of the atmosphere, both by adding additional amounts of gases naturally present, such as carbon dioxide and methane and also by the introduction of gases which do not occur naturally, such as CFCs (chlorofluorocarbons). It is worth noting that the sun emits ultraviolet (UV), visible and also infrared (IR) radiation (full electromagnetic spectrum.) This IR radiation is mainly absorbed by water vapor in the atmosphere and also contributes to the warming of the Earth. It is important to differentiate between the natural greenhouse effect, which is essential for life to exist, and the enhanced greenhouse effect . This is the additional effect caused by the anthropogenic emissions and it is what is generally thought to be causing global warming. When molecules interact with UV radiation the energy they absorb tends to break the compounds bonds. This is because the energy of a photon of UV radiation corresponds to transitions between electronic energy levels in a molecule, so when a molecule absorbs UV radiation it is excited to a higher electronic energy state which may result in bond fission. IR radiation is less energetic as the photons contain less energy. Rather than breaking bonds it causes them to vibrate. Advanced theory shows that a molecule will absorb IR radiation if the vibration causes a change in dipole moment. Consequently, nitrogen and oxygen are not IR active, but many of the gases present in the atmosphere in lower concentrations such as water vapor and carbon dioxide are. Information obtained and modified slightly from the chemistry of climate change: Vicky Wong Goal: To develop student knowledge of greenhouse gases.
Objectives: Students will discover greenhouse gases contributes to the greenhouse effect. Meets US National Science Standards S1, S2 and S6 Curriculum applications: Balancing Equations, Physical Chemical Properties, Structure and Function of molecules, Green Chemistry, Polarity, Dipole moments, Carbon sinks and acidification Materials: thin sandwich baggies (thicker bags don’t show desired results think cheap), packaging tape (optional to get better results the data will work without this and using regular clear tape around thermometer and a sealable baggie, 2 thermometer per group, Hydrogen peroxide 3% soln (6% works better), Yeast, lightbulb and lamp stand Teacher procedure: 1.

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