summer chem2011

Are parents actually protecting their children from getting hurt or are they doing the opposite when preventing kids from performing semi-dangerous acts? That’s the question many scientists are looking into when discussing the new safety regulations of public playgrounds. Because many parents are afraid of their toddlers accidentally falling off of playground jungle gyms, they have started to lower the heights of bars or eliminating them altogether. Though many parents believe that this will ultimately save the child from injuries such as concussions and broken arms, taking away the need for height and speed, dangerous but necessary, may have harmful effects on children, as they get older. Scientists have discovered that children that are not exposed to extreme heights or fast motion become more susceptible to have a fear of height when they are older. It is proven that kids need to have both speed and height in order to have healthy emotional development when dealing with more dangerous situations. For instance, if a child is prevented from going down a very steep slide in a park and is deprived of that experience for most of the important development age (2-5) that child could have a fear of heights; the same goes for high jungle gyms. Also, it is not even a proven fact that lower bars or lower play sets have a less of an injury rate then the higher more risky play toys; therefore, there is really no harm in having the higher structures. Also, children feel more of a sense of accomplishment when they finally reach the top of a high jungle gym because they completed a harder task then if they were to scale a four-foot-tall set of bars; there is nothing better than feeling like you have just reached the top of the world. Jungle gyms, though sometimes controversial due to their height, are an essential learning tool for children.

http://www.nytimes.com/2011/07/19/science/19tierney.html?_r=1&ref=science

The relationship that describes the relationship between the frequency of electromagnetic radiation and its energy is that there is a 1 to 1 relationship because as the frequency increases the energy increases.
Spectrum is a good term because it means a wide range and there is a wide range of the types of energy found in electromagnetic radiation.
Visible light is useful in plant synthesis because they help the plant produce carbohydrates, which are either consumed by the plant itself or are consumed by other animals. The non visible-more-powerful electromagnetic radiation can actually harm plants. UV-C is known to kill viruses and bacteria and could probably kill plants, while others like infrared could heat the plant till it dries out.
The main types of electromagnetic radiation are Ultraviolet radiation, visible radiation, and infrared radiation.

Ultraviolet radiation- needed for life because it provides vitamin D but can also harm and end life when found as UV-C. Visible light- energizes electrons and provides energy for photosynthesis. Infrared radiation- creates the heat we feel from the sun.

Ultraviolet light’s frequency is so high that it can kill viruses and bacteria while visible light has a lower frequency and is not as potent.
Infrared light can barely reach the surface because it is readily absorbed by CO₂ it is also held into the atmosphere by green house gases and part of the problem of global warming. Visible radiation is barely absorbed by the atmosphere with 90% of the radiation reaching Earth’s surface on a clear day. Uv radiation is has three subcategories with two being able to reach Earth’s surface and one that is completely absorbed, UV-C is completely absorbed and UV-A and UV-B can reach Earth.
The two main effects of solar radiation are global heating and photosynthesis can be done.
Hot asphalt will heat more readily than lake water because the asphalt is being directly bombarded with the radiation, while the lake water is more spread out and deeper so it is harder to heat.

Their density and surface.

Atmospheric CO₂helps maintain moderate temperatures because the gas prevents full contact with some of the sun’s harmful radiation and contains the heat inside our atmosphere. Water vapor protects the Earth from harmful rays through cloud cover and also helps absorb heat.
A. CO₂- burning wood and burning petroleum; two natural causes are plants decomposing and animals decomposing

CH₄- The methane emissions that come from factories and too many cows rooming around are two human activities that can increase the amount; Methane gas is emitted in fires and when plants decompose.

Changes that would cause the temp of the earth to:

Increase- More CO₂ and water vapor in the atmosphere would cause a certain increase of heat
Decrease- less than the normal amount of CO₂ in the atmosphere would cause earth to be cooler because it would not hold any heat in.

A green house is warmer on a sunny winter day because the glass traps the heat inside by allowing the heat in and a green house (has CO₂ from the plants inside) prevents the heat from leaving, which protects the plants from freezing.
On paper.
Three chemical reservoirs of carbon atoms are atmospheric CO₂ gas, solid calcium carbonate, and organic molecules.
Over time a particular carbon atom can be part of the atmosphere (as CO₂), biosphere (in humans), lithosphere (fossil fuels), and hydrosphere (limestone) because of the carbon cycle where carbon comes into the atmosphere and cycles through all of the substances listed above.

1-4 344

Human exposure to ultraviolet radiation is potentially more harmful then infrared because ultraviolet radiation has a higher frequency than infrared and is not as absorbed in the atmosphere.
Two essential roles played by visible solar radiation are photosynthesis and produces the visible color changes of the sky during a sunset
Drier regions experience more extreme weather conditions than humid regions because in humid regions the water vapor in the air prevents a lot of the solar radiation and heat from actually reaching the surface of the Earth.
Suppose Earth has a less dense atmosphere than it does now:

Average daytime temperatures would be extremely hot (hot enough to scramble a rock) because the amount of solar radiation that would get into our atmosphere would drastically change the weather conditions.
The nighttime temperatures would be extremely cold because the amount of CO₂ would be insufficient and not contain the reradiating heat coming from the earth.

p. 232 1-30

1. A hydrocarbon is a molecule made of hydrogen atoms and carbon atoms with a carbon backbone and hydrogen branches

2. Petroleum is easy to refine, non-expensive, produces a large amount of energy and products, and is easy to find.

3. Oil is crude because it is not a renewable resource that can be used when found in its original state in nature.

4. The U.S uses about 20 million barrels of petroleum daily:

1. The average number of barrels of petroleum used daily in the U.S for building purposes is 4,000,000 barrels

2. On average 16,000,000 barrels of fuel are burned daily in the U.S

3. Gasoline, petrochemicals, and diesel fuel oil are obtained from crude oil.

4. 4 household items made from petroleum

a. Petroleum jelly, wax, cosmetics, and pharmaceuticals

b. The materials that could be substituted are certain kinds of plants or pigments. Also natural pharmaceuticals.

5. Questions about figure 3.4

a. The world region that has the most petroleum reserves relative to its population is the Middle Eastern are.

b. Western Europe has the least reserves

6. Continued:

a. The regions that consume greater proportions of the supply than they posses are The U.S and Western Europe

b. The regions that use smaller supply of the petroleum levels Central and South America, the Middle East, and Africa.

7. Under distillation density could be used to separate two different liquids.

8. Acetone and water would be the easiest to separate because water has a much higher boiling point then acetone; therefore, there is no chance of any water evaporating when the acetone does.

9. On paper

10. Fractional distillation distills a substance in fractions and creates different physical states of the substance, which differs from regular distillation because regular distillation leaves all the substances in their liquid state.

11. From light- heating and cooking fuel, petrochemicals, and starting material for plastics; from intermediate- heating fuel, petroleum gas, and kerosene; from heavy- petroleum jelly, wax, and road oils and asphalt.

12. I would expect the bottom fraction to have the highest boiling point because they are solids.

13. In order to further separate the components of each fraction you could perform distillation a second time.

14. Ranking for boiling points- Methane, pentane, hexane, and octane. The reason is the higher amount of hydrogen the higher the boiling point.

15. A covalent bond is a bong formed between atoms when they share their valence electrons.

16. Atoms with filled outer electron shells do not form covalent bonds because they are stable and do not have room for any more electrons.

17. The analogy describes the way that shared electrons hold together because they both equally want the shared electrons to make them stable like the noble gases and they are not willing to let go unless the bond is severed (the sock is taken away).

18. The information that a structural formula conveys is the shape of a three dimensional molecule, while a molecular formula just states the atoms present.

19. A structural formula is an inadequate representation of an actual molecule because it does not show how the 3D version of the atom looks.

20. On paper.

21. The four dots shown by the Lewis dot structure are the representations of the valence electrons. The valence electrons are in the outer shell and are the electrons available for sharing.

22. Use the general molecular formula:

a. 9- C₉H₂₀

b. 16- C₁₆H₃₄

c. 10- C₁₀H₂₂

d. 18- C₁₈H₃₈

23. The molar mass of each alkane listed:

a. 128g

b. 226g

c. 142g

d. 254g

24. Name and give the molecular formula for the alkane with a molar mass of

a. 44g/mol- Heptane and C₇H₁₆

b. 72g/mol- help!

25. The –ane implies that the carbon-carbon bonding in hexane is that its an alkane.

26. Yes the models are isomers of each other because they have the same chemical formula with the CH₃s on the ends of the molecules, but they have different layouts and branches.

27. On paper

28. The shortest-chain alkane that can demonstrate isomerism is CH₄

29. Both representations are correct because a linear chain and a zigzag chain have the same chemical formula and layout but with one having a more even pattern.

30. A. On paper

a. A branched chain will have a lower boiling because it has less molecule-to-molecule contact.

31. Which of each pair would have the lower boiling point? Describe why:

a. A short, straight chain or a long, straight chain? A short straight chain will have a lower boiling point because it is easier to separate and takes less time to separate.

b. A short, branched chain or a long, branched chain. A short branched chain would have a lower boiling point because the branched chain would be denser and, therefore, the shorter the chain the easier to separate.

c. A short, branched chain or a long, straight chain? A short branched chain would have a lower boiling point because it has less molecule to molecule contact

P 258 1-10

1. Petroleum is sometimes considered “buried sunshine” because it is technically fossilized plants that once performed photosynthesis with aid from the suns rays.

2. Define and give on example of

a. Potential energy- a rubber ball on the ground has potential energy

b. Kinetic energy- a rubber ball kicked on the ground

3. In chemical reactions chemical bonds are broken to form new bonds

4. A molecule of methane has more potential energy because it can be easily burned.

5. Classify each of the following as primarily a demonstration of kinetic energy or potential:

a. Potential energy

b. Potential energy

c. Kinetic energy

d. Potential energy

e. Kinetic energy

6. Energy is required to break chemical bonds because energy is needed to make the chemical bonds

7. Determine whether exo- or endothermic:

a. Burning wood in a campfire is endothermic because it is a chemical reaction and the bonds are breaking

b. Cracking large hydrocarbon molecules is exothermic because new bonds are being made

c. Digesting a candy bar is endothermic because bonds are being broken and exothermic because new bonds are forming.

8. The quantity of energy stored in the reactants is greater than that of the energy stored in the products because most of the potential energy was transferred into kinetic energy

9. On paper

10. The law of conservation of energy states that energy cannot be created or destroyed.