4 Greenhouse EffectEnergy from the Sun drives the Earth's weather and climate. The Earth absorbs energy from the Sun, and also radiates energy back into space. However, much of this energy going back to space is absorbed by “greenhouse” gases in the atmosphere (see Figure 1 of Greenhouse Effect). Because the atmosphere then radiates most of this energy back to the Earth’s surface, our planet is warmer than it would be if the atmosphere did not contain these gases. Without this natural “greenhouse effect”, temperatures would be about 60ºF lower than they are now, and life as we know it today would not be possible.During the past century humans have substantially added to the amount of greenhouse gases in the atmosphere by burning fossil fuels such as coal, natural gas, oil and gasoline to power our cars, factories, utilities and appliances. The added gases — primarily carbon dioxide and methane — are enhancing the natural greenhouse effect, and likely contributing to an increase in global average temperature and related climate changes.
5 Changes in Earth’s orbit Changes in sun’s intensity- Natural Causes:Changes in Earth’s orbitChanges in sun’s intensity-Volcanic Eruptions- put CO2 and other greenhouse gases into atmosphere
9 What is Acid Rain?Acid rain- a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids.The precursors, of acid rain formation result from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur dioxide (SO2) and nitrogen oxide (NOx) resulting from fossil fuel combustion.In the United States, roughly 2/3 of all SO2 and 1/4 of all NOx come from electric power generation that relies on burning fossil fuels, like coal. Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds.The result is a mild solution of sulfuric acid and nitric acid. When sulfur dioxide and nitrogen oxides are released from power plants and other sources, prevailing winds blow these compounds across state and national borders, sometimes over hundreds of miles.
11 Acid Rain Wet Deposition Wet Deposition refers to acidic rain, fog, and snow. If the acid chemicals in the air are blown into areas where the weather is wet, the acids can fall to the ground in the form of rain, snow, fog, or mist. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depends on several factors, including how acidic the water is; the chemistry and buffering capacity of the soils involved; and the types of fish, trees, and other living things that rely on the water.Dry DepositionIn areas where the weather is dry, the acid chemicals may become incorporated into dust or smoke and fall to the ground through dry deposition, sticking to the ground, buildings, homes, cars, and trees. Dry deposited gases and particles can be washed from these surfaces by rainstorms, leading to increased runoff. This runoff water makes the resulting mixture more acidic. About half of the acidity in the atmosphere falls back to earth through dry deposition.
12 pH Scale pH is the measure of how acidic or how basic a substance is It ranges from 0-14A pH of 7 is neutral, a pH of less than 7 is acidic, and a pH greater than 7 is basicThe pH scale is logarithmic, meaning… each whole pH value below 7 is ten times more acid than the next higher valueFore example, a pH of 4 is ten times more acidic than a pH of 5 and a hundred times more acidic than a pH of 6.Pure water is neutral, but when chemicals are mixed with water, the mixture can be come acidic or basic.
14 Acid LabThe strength of acids and bases depends on the relative number of two chemical substances:H+ (Hydrogen ion)OH- (Hydroxide ion)Example: H2SO4 is sulfuric acidIn water, H2SO4 breaks down into H+ and HSO4 ions. The HSO4- ions break down further to produce another hydrogen ion (H+) and SO4- ionsThese free floating H+ ions make a substance acidicThe more free hydrogen ions in a solution, the stronger the acid is.
15 Acid LabThe pH scale tells us the relative amount of H+ ions in the solution.When the relative number of hydrogen ions is exactly equal to the number of hydroxide ions, they combine chemically and cancel each other’s reactivity.What substance do we get when we combine an H+ ion with an OH- ion?H2O (Water)
16 Rain Water Rainwater is slightly acidic (pH between 5.6 and 5.7) Why? Some molecules of carbon dioxide from the atmosphere dissolve into the water and split, releasing the H+ ions into the raindrop.What happens to an ecosystem if the rainwater is too acidic?Effect of acid precipitation on a body of water depends on the nature of the rocks and soils in the watershed.A watershed with soils high in calcium content or rocks containing calcium carbonate can buffer acid precipitationThink about how Alka Seltzer (Calcium Carbonate) neutralizes stomach acid
17 Acid LabYou are going to design your own lab to answer a question you might have about acid precipitation or just the general nature of acids and bases.Examples of possible labs:pH of different sodaspH of different foodspH of household productsWhat is the best antacid?Compare soil samples from around the valleyPage 38-Write the question you want to answerList the variable you will be observing and what data you will be collectingOn a separate piece of paper, compile a list of materials you need for this lab and have me check it when you are done.