Helpful Test Taking Strategies

                        Before
-Preparation for your first test should begin on the first day of class; this includes paying attention during class, taking good notes, studying, completing homework assignments and reviewing study materials on a regular basis.
-Budget your time, make sure you have sufficient time to study so that you are well prepared for the test.
-Go to review sessions, pay attention to hints that the instructor may give about the test. Take notes and ask questions about items you may be confused about.
-Ask the instructor to specify the areas that will be emphasized on the test.
-Make sure you go to the class right before the test; it's another prime time for the instructor to give out more hints or the format of the test.
-Go over any material from practice tests, HW's, sample problems, review material, the textbook, class notes...
-Eat before a test. Having food in your stomach will give you energy and help you focus but avoid heavy foods which can make you groggy.
-Don't try to pull an all nighter. Get at least 3 hours of sleep before the test (normally 8 hours of sleep a night is recommended but if you are short on time, get at least 3 hours so that you'll be well rested enough to focus during the test).
-Put the main ideas/information/formulas onto a sheet that can be quickly reviewed many times, this makes it easier to retain the key concepts that will be on the test.
-Try to show up at least 5 minutes before the test will start.
-Set your alarm and have a backup alarm set as well.
-Go to the bathroom before walking into the exam room. You don't want to waste anytime worrying about your bodily needs during the test.






                                      
                                                  During
-Bring at least two pens/pencils with good erasers, a calculator with enough batteries and any other resources that your instructor allows you to.
-Bring a watch to the test so that you can better pace yourself.
-Keep a positive attitude throughout the whole test and try to stay relaxed. If you start to feel nervous take a few deep breaths to relax.
-Keep your eyes on your own paper, you don't want to appear to be cheating and cause unnecessary trouble for yourself.
-When you first receive your test, do a quick survey of the entire test so that you know how to efficiently budget your time.
-Do the easiest problems first. Don't stay on a problem that you are stuck on, especially when time is a factor.
-Do the problems that have the greatest point values first.
-Pace yourself, don't rush . Read the entire question and pay attention to the details.
-Ask the instructor for clarification if you don't understand what they are asking for on the test.
-Write legibly. If the grader can't read what you wrote, they'll most likely mark it wrong.
-Always read the whole question carefully. Don't make assumptions about what the question might be.
-If you don't know an answer, skip it. Go on with the rest of the test and come back to it later. Other parts of the test may have some information that will help you out with that question.
-Don't worry if others finish before you. Focus on the test in front of you.
-If you have time left when you are finished, look over your test. Make sure that you have answered all the questions. Only change an answer if you misread or misinterpreted the question because the first answer that you put is usually the correct one. Watch out for careless mistakes and proofread your essay and/or short answer questions.

-Double check to make sure that you put your first and last name on the test.

Nitrogen Based Eplosive Compounds

Trinitrotoluene (TNT) -
Trinitrotoluene is better known as it's initials TNT. It is an important explosive, since it can very quickly change from a solid into hot expanding gases. Two moles of solid TNT almost instantly changes to 15 moles of hot gases plus some powdered carbon, which gives a dark sooty appearance to the explosion. This is where another explosive. TNT is explosive for two reasons. First, it contains the elements carbon, oxygen and nitrogen, which means that when the material burns it produces highly stable substances (CO, CO₂ and N₂) with strong bonds, so releasing a great deal of energy.

Nitroglycerin -

Nitroglycerin is an oily, colourless liquid, but also a high explosive that is so unstable that the slightest jolt, impact or friction can cause it to spontaneously detonate. Since the molecule contains oxygen, nitrogen and carbon, when it explodes a lot of energy is released as the atoms rearrange to form new molecules with strong, stable bonds, like N₂ and CO. http://www.ch.ic.ac.uk/rzepa/mim/environmental/html/nitroglyc_text.htm%20Hexahydro

Cfc's & Ozone Depletion



 

The term “ozone” has appeared in numerous magazine and newspaper articles and has been a subject of discussion on both radio and television. Despite all the publicity surrounding this term, however, many people are still confused by it. The confusion arises from the fact that ozone is both beneficial and harmful. We know that the ozone layer in the upper atmosphere acts as a filter for the sun's ultraviolet rays, reducing the amount of radiation that reaches the earth's surface. At ground level, though, high concentrations of ozone can be harmful. Ozone gas forms a layer all around the earth high in the stratosphere. It serves as a vital and effective protective barrier from the sun's ultraviolet rays. In recent years, scientists have sounded alarms internationally about the depletion of the ozone layer, citing chemical pollution as the major cause.
A specific class of chemical compounds called chlorofluorocarbons (CFCs) are most often identified as ozone destroyers. CFCs were once widely used in everything from air conditioner coolants to the propellant in aerosol cans but have now been banned in most developed nations, including the U.S.
Many scientists believe much more needs to be done to protect the ozone layer, and international efforts are ongoing.
 Ozone pollution is really an increase in the concentration of ozone in the air at ground level. Because sunlight has a critical role in its formation, ozone pollution is principally a daytime problem in the summer months. Ground-level ozone is produced when sunlight combines with hydrocarbons and nitrogen oxide, two compounds produced by cars, trucks, factories, and power-generating plants, and found wherever gasoline, diesel fuel, kerosene, oil, or natural gas are combusted. Urban areas with heavy traffic, and large industrialized communities, are the primary areas with ozone problems.
  The cause of ozone depletion is the increase in the level of free radicals such as hydroxyl radicals, nitric oxide radicals and atomic chlorine and bromine. The most important compound, which accounts for almost 80% of the total depletion of ozone in the stratosphere are chlorofluorocarbons (CFC). These compounds are very stable in the lower atmosphere of the Earth, but in the stratosphere, they break down to release a free chlorine atom due to ultraviolet radiation. A free chlorine atom reacts with an ozone molecule (O3) and forms chlorine monoxide (ClO) and a molecule of oxygen. Now chlorine monoxide reacts with an ozone molecule to form a chlorine atom and two molecules of oxygen. The free chlorine molecule again reacts with ozone to form chlorine monoxide. The process continues and the result is the reduction or depletion of ozone in the stratosphere.



  Ozone (O3) is found in two different parts of our atmosphere. Ground level ozone, a human health irritant and component of smog, is found in the lower atmosphere (troposphere) and has nothing to do with the "ozone hole." However, ozone in the stratosphere—the layer of atmosphere above the troposphere accounts for the vast majority of atmospheric ozone. Stratospheric ozone is protective of human health as it absorbs ultraviolet radiation from the sun, preventing the radiation from hitting Earth's surface and harming living organisms from this biologically dangerous radiation. 

The thickness of the polar stratospheric ozone layer depends on the rate of production of ozone in the tropical stratosphere, the movement of ozone from the tropics to the poles, the amount of ultraviolet radiation from the Sun, the polar stratospheric cloud cover, and the chemical reactions between the ozone and ozone- depleting substances. Each of these factors might be affected by climate change. Poleward motions in the stratosphere, which increase polar concentrations of ozone, as well as the strength of the polar stratospheric vortices, which decrease ozone via PSC formation, are both expected to increase as temperatures rise in the lower atmosphere. Yet temperatures in the lower stratosphere are decreasing as a result of increased carbon and other heat-trapping emissions. The reason for this apparent paradox—increasing temperatures at the Earth's surface and decreasing temperatures in higher parts of the atmosphere—can be explained using the blanket analogy. Carbon dioxide and other heat-trapping gases rise into the atmosphere, spread around the globe, and act like a blanket holding in heat around Earth. This blanket also protects the warm surface of the Earth from the cold air above it. As heat-trapping gas concentrations increase, the blanket thickness also increases. This further warms the Earth’s surface; heats the blanket itself; and traps more heat in the lower atmosphere. Heat that normally (i.e. before blanket thickening) would escape the lower atmosphere and enter the stratosphere no longer does so, leaving the stratosphere cooler. Cooling of the lower polar stratosphere enhances PSC formation, and thus contributes to ozone loss. It appears unlikely that the decrease in ozone-depleting substances will lead to restabilization of the pre-1980 stratospheric ozone layer because of the competing and uncertain effects of further climate change.

Scientific Explanation Behind Various

Causes Of Climate Change.

The causes of climate change can be divided into two categories, human and natural causes.

It is now a global concern that the climatic changes occurring today have been speeded up because of man's activities.

The natural variability and the climate fluctuations of the climate system have always been part of the Earth’s history however there have been changes in concentrations of greenhouse gases in the atmosphere growing at an unprecedented rate and magnitude. The United Nations, governments and many top scientists around the world believe that we must act now to stabilise and arrest further changes.

To understand climate change fully, the causes of climate change must be first identified. Scientists divide the causes into two categories, natural and human causes.

Natural Causes of Climate Change

The earth’s climate is influenced and changed through natural causes like volcanic eruptions, ocean current, the earth’s orbital changes and solar variations.

Volcanic eruptions - When a volcano erupts it throws out large volumes of sulphur dioxide (SO2), water vapour, dust, and ash into the atmosphere. Large volumes of gases and ash can influence climatic patterns for years by increasing planetary reflectivity causing atmospheric cooling. Tiny particles called aerosols are produced by volcanoes. Because they reflect solar energy back into space they have a cooling effect on the world. The greenhouse gas, carbon dioxide is also produced however the CO2 produced is insignificant when compared to emissions created by humans.Ocean current - The oceans are a major component of the climate system. Ocean currents move vast amounts of heat across the planet. Winds push horizontally against the sea surface and drive ocean current patterns. Interactions between the ocean and atmosphere can also produce phenomena such as El Niño which occur every 2 to 6 years. Deep ocean circulation of cold water from the poles towards the equator and movement of warm water from the equator back towards the poles. Without this movement the poles would be colder and the equator warmer. The oceans play an important role in determining the atmospheric concentration of CO2. Changes in ocean circulation may affect the climate through the movement of CO2 into or out of the atmosphere.
Earth orbital changes - The earth makes one full orbit around the sun each year. It is tilted at an angle of 23.5° to the perpendicular plane of its orbital path. Changes in the tilt of the earth can lead to small but climatically important changes in the strength of the seasons, more tilt means warmer summers and colder winters; less tilt means cooler summers and milder winters. Slow changes in the Earth’s orbit lead to small but climatically important changes in the strength of the seasons over tens of thousands of years. Climate feedbacks amplify these small changes, thereby producing ice ages.

Solar variations - The Sun is the source of energy for the Earth’s climate system. Although the Sun’s energy output appears constant from an everyday point of view, small changes over an extended period of time can lead to climate changes. Some scientists suspect that a portion of the warming in the first half of the 20th century was due to an increase in the output of solar energy. As the sun is the fundamental source of energy that is instrumental in our climate system it would be reasonable to assume that changes in the sun's energy output would cause the climate to change. Scientific studies demonstrate that solar variations have performed a role in past climate changes. For instance a decrease in solar activity was thought to have triggered the Little Ice Age between approximately 1650 and 1850, when Greenland was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.

Current global warming however cannot be explained by solar variations. Some examples are evidenced such as since 1750, the average amount of energy coming from the Sun either remained constant or increased slightly.
If global warming was caused by a more active sun, then scientists would expect to see warmer temperatures in all layers of the atmosphere. They have only observed a cooling in the upper atmosphere, a warming at the surface and in the lower parts of the atmosphere. This is due to greenhouse gasses capturing heat in the lower atmosphere. Also climate models that include solar irradiance changes cannot reproduce last century's observed temperature trend without including a rise in greenhouse gases.

The causes of climate change continued
Increase in global temperatures - Inter-government Panel

The most recent assessment report from the Intergovernmental Panel on Climate Change (IPCC) says that the earth’s average temperature has risen by 0.74 degrees in the period from 1906 to 2005, and that the average temperature will continue to rise.

The greenhouse effect is a natural mechanism that retains the heat emitted from the earth’s surface. The earth’s average temperature is at the moment around 14 degrees celsius (57 degrees fahrenheit). If the natural greenhouse effect did not exist, the average temperature would be around minus 19 degrees celsius (minus 2 degrees fahrenheit).

The greenhouse effect is caused by a range of different gases in the earth’s atmosphere. Water vapour makes the most significant contribution to the greenhouse effect, followed by CO2. The atmospheric content of greenhouse gases – in particular CO2 – and the consequences for the climate are being discussed because the content of these gases in the atmosphere has risen precipitously in a period covering approximately the latest 250 years, and especially the last 50.

At present the concentration of CO2 in the atmosphere is about 385 ppm (parts per million). Before industrialization it was about 280 ppm. Analyses of air contained in ice from the Antarctic ice cap show that there is far more CO2 in the air today than at any time in the last 650,000 years.

The consequence is that the greenhouse effect is becoming stronger, and therefore the earth is becoming warmer. How much warmer has, however, been a matter of dispute. The most recent assessment report from the IPCC is from 2007. It concludes that the earth’s average temperature has risen by 0.74 degrees in the period from 1906 to 2005. The warming is stronger over land areas than over the sea, and accordingly it is strongest in the northern hemisphere. At the same time occurrences of heat waves and violent downpours have also increased, the oceans have risen, and the ice at the world’s poles and on its mountains has begun to melt. All of these effects are predictable in the event of global warming.

Notes: Chemistry In The Community

Kinetic Molecular Theory
The experimental observations about the behavior of gases discussed so far can be explained with a simple theoretical model known as the kinetic molecular theory. This theory is based on the following postulates, or assumptions.
Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion.
These particles move in a straight line until they collide with another particle or the walls of the container.
These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.
There is no force of attraction between gas particles or between the particles and the walls of the container.
Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container.
The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.
The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules), all of which are in constant, random motion. The rapidly moving particles constantly collide with each other and with the walls of the container. Kinetic theory explains macroscopic properties of gases, such as pressure, temperature, or volume, by considering their molecular composition and motion. Essentially, the theory posits that pressure is due not to static repulsion between molecules, as was Isaac Newton's conjecture, but due to collisions between molecules moving at different velocities.
While the particles making up a gas are too small to be visible, the jittering motion of pollen grains or dust particles which can be seen under a microscope, known as Brownian motion results directly from collisions between the particle and gas molecules. As pointed out by Albert Einstein in 1905, this experimental evidence for kinetic theory is generally seen as having confirmed the existence of atoms and molecules.
Boyle's Law
 (sometimes referred to as the Boyle-Mariotte law) is one of many gas laws and a special case of the ideal gas law . Boyle's law describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system. A law stating that the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature.
Boyle's law explains an inverse relationship between the volume and pressure of a gas. For example, if the volume of a gas doubled, the pressure it exerted would be cut by half. If the volume tripled, the pressure would be a third of what it was before.
Boyle's law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas. The before and after volumes and pressures of the fixed amount of gas, where the before and after temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:

Charles's law (also known as the law of volumes) is an experimental gas law which describes how gases tend to expand when heated the volume V of given mass of a gas is directly proportional to its absolute temperature.Charles studied the compressibility of gases nearly a century after Boyle. In his experiments he observed "At a fixed pressure, the volume of a gas is proportional to the temperature of the gas." Charles' Law describes the direct relationship of temperature and volume of a gas. Assuming that pressure does not change, a doubling in absolute tempature of a gas causes a doubling of the volume of that gas. A drop of absolute temperature sees a proportional drop in volume.The law can also be usefully expressed as follows:

The expression Gay-Lussac's law which concern the properties of gases, though it is more usually applied to his law of combining volumes, the first listed here. One law relates to volumes before and after a chemical reaction while the other concerns the pressure and temperature relationship for a sample of gas.
The law of combining volumes states that, when gases react together to form other gases, and all volumes are measured at the same temperature and pressure:The ratio between the volumes of the reactant gases and the products can be expressed in simple whole numbers.

Kinetic Molecular Theory Of Gases

The kinetic theory of gases is the study of the microscopic behavior of molecules and the interactions which lead to macroscopic relationships like the ideal gas law. The Kinetic Molecular Theory of Gases begins with five postulates that describe the behavior of molecules in a gas. These postulates are based upon some simple, basic scientific notions, but they also involve some simplying assumptions .
                                                                Postulates

• A gas consists of individual particles in constant and random motion.
• The individual particles have negligible volume.
• The individual particles do not attract or repel one another in any way.
• The pressure of the gas is due entirely to the force of the collisions of the gas particles with the walls of the container.



Galindo, Sarah . Period 3

1.) How many blog posts have you completed this semester ? What grade would you give your self for your blogs ?
I Have completed 7 blogs this semester . I would give myself a C .

2.) Predict your final exam grade and your final semester grade ( average 3 test & blog ) .
I predict my final exam grade will be a d or d+ & my final semester grade will be a d- .

3.) Research fun chemistry. Keeping in mind safety, What would you like to learn next semester ?
Next semeser i would like to do more fun & interesting labs & fun projects .