Chem 1100 Lecture 7 Outline of Last Lecture I. Energy of LightII. What happens when light hits matter?III. Types of RadiationIV. The Chapman CycleV. Cause for ConcernVI. Why do we care about energy?Outline of Current Lecture I. The Greenhouse EffectII. The History of Our AtmosphereIII. Shapes of MoleculesIV. Light & MoleculesCurrent LectureI. The Greenhouse Effecta. Comparing Earth to Venus (Volume of atmosphere is relatively the same, as well as the size)b. Calculate a temperature based solely on distance Earth is 0 F Venus 212 Fc. Calculate a temperature actually: Earth is 59 F Venus 840 Fd. Why? Heat is held in longer by Co2 and H2O in the atmosphere. e. The heat energy comes in from the sun and some of it is absorbed by the atmosphere, the rocks, the water, some doesn’t even make it to the planet but reflects off the surface. f. The Greenhouse Effect is a good thing. It is not the same as global warming.g. Global warming is more of The Greenhouse Effect running wild.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.h. Greenhouse Gases: Absorb IR radiation, which allows them to trap heat and hold the heat in so our planet can remain a certain temperature. i. Co2 & H20 (also methane: Ch4 to a lesser degree) these compounds hold in heat.j. No significant change of the amount of water in the atmosphere. We can’t change that. The majority of our planet is made of water.k. We are looking to change the amount of Co2 and methane. Co2 is on the rise. More now than 150 years ago. Earth temperature has changed.l. Around 150 years ago the Industrial Revolution happened. A lot of burning of coal and oil resulted in the man made production of Co2. m. Greenhouse Effect: process where gases trap heat. Heat stays and warms the planet. Needed for life – planet would freeze otherwise. n. Too much of the greenhouse effect can be bad because that’s where global warming comes into place. An average return of energy that is greater than 80%, if the earth can’t get rid of at lest 80% of the absorbed energy from during the day, we will see an increase in global temperature. “Enhanced Greenhouse Effect”II. History of Our Atmospherea. Early atmosphere there was about a 1000x’s more CO2 than there is today. Bacteria used Co2 to make sugars. The sugars were then broken down for energy,to make cell walls, and to store energy. b. Very complicated process: The bacteria would take Co2 combine it with water, make sugars, C6H12O6 is the compound for sugar. They reproduce rapidly, because they don’t have long to live. 6CO2 + 6H20  C6H12O6 + 6O2c. How do we know? Core samples from the ocean. Soil samples. Things die in the ocean and they sink to the bottom and the high pressure the ocean exerts on them they get compacted into the soil. Bacterial remains tell temperature. The temperature must have been high enough to allow these bacteria to thrive. The bacteria have some iron in them as a mineral, and it is magnetic. The magnetic alignment will point to the magnetic core. The Earth’s magnetic core has moved since these bacteria existed because we can tell by the way the bacteria was pointing when they died. It’s in a different direction then it is now. d. “Heavy Water” composition of Ice. More heavy water = higher temperature.- Trapped bubbles: tell concentration of CO2 when bubble was formed. - Even though the bacterial population and the heavy water composition are unrelated but the predicted temperature agrees. The temperature of the planet changes, goes through ups and downs, showing some ice ages. For that reason we suspect that something is happening.- Theory: Maybe global warming is caused by increased levels of greenhouse gases. CO2 and CH4.- Maybe there’s something else that’s causing these high temperatures. -Fact: CO2 and Ch4 trap heat and do contribute to global warming. -Other Factors: Changes in our Earth’s orbit. There are some variations. Sometimes its been closer to the sun sometimes its been farther away. Leads to major and minor ice ages. But that’s not what has created the changes in temperature today. Airborne dust – volcanic activity. Cloud cover – weather patterns. Greenhouse gases. e. The Futuref. Based on date from the last 100 years, Co2 concentration has risen by 25%. And the average temperature has increased to a half degree to almost ¾ of a degree Celsius. g. Currently: doubling the CO2 concentration. +1.8-6.3 Ch. (2.5 – 10.4 F by 2100)i. CO2 is a major part of the greenhouse effect. Earth’s average temperature IS increasing. III. Shapes of Moleculesa. Greenhouse gases: CO2, CH4, N2O, O3, H2O, CFCsb. Not Greenhouse gases: O2, N2, Arc. Why the difference? Their shape! How molecules are shaped determines how different kinds of light react with them. Infrared makes molecules vibrate. The vibrational energy is released as heat. d. VSEPR (Lewis structures 2D, Reality 3D)i. Valence Shell Electron Pair Repulsionii. Valence Shell – outer electronsiii. Electron Pair Repulsion: electrons repelling each otheriv. Bonds are made of electrons, negatively charged, repel each other (still attracted to protons), they want to be as far apart as possible.v. Example: Methane Ch4 : tetrahedralvi. A wedge and dash drawing. It’s a derivative of the lewis structure. It shows the molecule in more of a 3D example. Wedge means its comingout of the paper towards you and the dash means its going into the paper away from you. As far apart as 4 bonds can be 109.5vii. You can have 1 wedge and 1 dash MAXIMUM.viii. Never draw solid lines in between the wedges and the dashes. ix. The solid lines are interpreted as being in the plane of the paper. They are not going away or towards you. x. Lewis dot structure, The Lewis Structure, Wedge & Dash Drawing, Space Filling Model ^^^^^Shown above in order from left to right.xi. ANOTHER EXAMPLE Ammoniaxii. Why is the 107.3 smaller than 109.5? Because the lone pair of electrons has a greater repulsive force than electrons that are in a bond. Rather than be shared between two molecules they are in the sole possession of that nitrogen so they are hanging around closer to the nucleus rather than being stretched between two atoms. So that means that they are going to repel the other guys more and that anglebetween the nitrogen and hydrogen bonds is going to be compressed more than the ones in the 109.5 angle.xiii. The