Ozone Depletion

Take care of our planet:

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 for 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 stratospheric ozone layer shields life on Earth from the Sun’s harmful ultraviolet radiation. Chemicals that destroy ozone are formed by industrial and natural processes. With the exception of volcanic injection and aircraft exhaust, these chemicals are carried up into the stratosphere by strong upward-moving air currents in the tropics. Methane (CH₄), chlorofluorocarbons (CFCs), nitrous oxide (N₂O) and water are injected into the stratosphere through towering tropical cumulus clouds. These compounds are broken down by the ultraviolet radiation in the stratosphere. Byproducts of the breakdown of these chemicals form “radicals”—such as nitrogen dioxide (NO₂) and chlorine monoxide (ClO)—that play an active role in ozone destruction. Aerosols and clouds can accelerate ozone loss through reactions on cloud surfaces. Thus, volcanic clouds and polar stratospheric clouds can indirectly contribute to ozone loss.


 

(CFCs, freons, halons.) CFCs and other contributory substances are referred to as ozone-depleting substances (ODS).

Since the ozone layer prevents most harmful UVB wavelengths (280–315 nm) of ultraviolet light (UV light) from passing through the Earth's atmosphere, observed and projected decreases in ozone have generated worldwide concern leading to adoption of the Montreal Protocol that bans the production of CFCs, halogens  and other ozone-depleting chemicals such as carbon tetrachloride and trichloroethane. It is suspected that a variety of biological consequences such as increases in skin cancer, cataracts, damage to plants, and reduction of plankton populations in the ocean's photic zone may result from the increased UV exposure due to ozone depletion.




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Global Warming

Green house effect:

The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface.Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F).The major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect; carbon dioxide (CO₂), which causes 9–26 percent; methane (CH₄), which causes 4–9 percent; and ozone (O₃), which causes 3–7 percent.

Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO₂, methane, tropospheric ozone, CFCs and nitrous oxide.

Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation.
Most of the observed temperature increase since the middle of the 20th century has been caused by increasing concentrations of greenhouse gases, which result from human activities such as the burning of fossil fuel and deforestation.

Consequencies:An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts.

Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice.



Other likely effects of the warming include more frequent and intense precipitation events, extreme weather events, species extinctions due to shifting isotherms, and changes in agricultural yields.

Balancing chemical reactions

1. Identify each element found in the equation. The number of atoms of each type of atom must be the same on each side of the equation once it has been balanced.
2. If possible, start with an element found in one compound on each side of the equation. Change the coefficients (the numbers in front of the compound or molecule) so that the number of atoms of the element is the same on each side of the equation. Remember! To balance an equation, you change the coefficients, not the subscripts in the formulas.
3. Once you have balanced one element, do the same thing with another element. Proceed until all elements have been balanced. It's easiest to leave elements found in pure form for last.
4. Check your work to make certain the charge on both sides of the equation is also balanced.

Example of Balancing a Chemical Equation

? CH₄ + ? O₂ → ? CO₂ + ? H₂O
Identify the elements in the equation: C, H, O
Identify the net charge: no net charge, which makes this one easy!

1. H is found in CH₄ and H₂O, so it's a good starting element.
2. You have 4 H in CH₄ yet only 2 H in H₂O, so you need to double the coeffient of H₂O to balance H. 1 CH₄ + ? O₂ → ? CO₂ + 2 H₂O
3. Looking at carbon, you can see that CH₄ and CO₂ must have the same coefficient. 1 CH₄ + ? O₂ → 1 CO₂ + 2 H₂O
4. Finally, determine the O coefficient. You can see you need to double the O₂ coefficient in order to get 4 O seen on the product side of the reaction. 1 CH₄ + 2 O₂ → 1 CO₂ + 2 H₂O
5. Check your work. It's standard to drop a coefficient of 1, so the final balanced equation would be written: CH₄ + 2 O₂ → CO₂ + 2 H₂O

 

Plastics for grade 9

An addition polymer is a polymer which is formed by an addition reaction, where many monomers bond together via rearrangement of bonds without the loss of any atom or molecule. This is in contrast to a condensation polymer which is formed by a condensation reaction where a molecule, usually water, is lost during the formation.The discharge of plastics after usage cause a pollution problem ,to decrease this problem we depend on recycling especially for thermoplastics.

To assist recycling of disposable items, the Plastic Bottle Institute of the Society of the Plastics Industry devised a now-familiar scheme to mark plastic bottles by plastic type. A plastic container using this scheme is marked with a triangle of three "chasing arrows", which encloses a number giving the plastic type:

1. PET (PETE), polyethylene terephthalate
2. HDPE, high-density polyethylene
3. PVC, polyvinyl chloride
4. LDPE, low-density polyethylene,
5. PP, polypropylene
6. PS, polystyrene

Plastics type marks: the resin identification code



Some products and the type of plastic they are manufactured from:

LDPE





Polyethylene bag





polystyrene



PVC pipes







PP



HDPE

Review on chemical reactions for Grade :7

A chemical reaction is defined as the process, wherein a set of chemical substances react with each other, which leads to their conversion into other different forms. The initial substances used the reaction are collectively called reactants, while the final substances formed after the reaction are known a products. In general, the chemical properties of the reactants and products are different from each other.

Aerobic Respiration
Do you know indulging in physical movements is associated with a chemical reaction? The process requires energy, which is yielded by aerobic respiration. Over here, respiration helps breaks down glucose (an energy source) into water, carbon dioxide and energy in form of ATP (adenosine triphosphate). The balancedcellular respiration equation is represented as:

C₆H₁₂O₆ + 6O₂ → 6CO₂+ 6H₂O + Energy

Photosynthesis
Photosynthesis is the process by which green plants manufacture their own food. This occurs in presence of sunlight and other raw materials, namely carbon dioxide and water. The chlorophyll pigment harvests the light energy from sunlight, which is then converted into glucose by the phenomenon of photosynthesis. In short, it is the opposite of aerobic respiration. Theequation for photosynthesis is:

6 CO₂+ 6 H₂O + Light energy → C₆H₁₂O₆ + 6 O

<sub>Propane Grill
Have you ever prepared meat in a propane grill? The meat placed over the burner is cooked with the help of heat energy released after burning of propane gas. Thus, propane is the reactant which when burnt with the help of oxygen gives heat energy and other byproducts. Check out the balanced equation for the combustion reaction that take place in a propane grill::

C3H8 + 5O2 → 4H2O + 3CO2 + energy</sub>

Look at the cases below indicate whether there is a chemical reaction taking place .

a-water is freezed ,melted ,then evaporated .

b-dissolve sugar in water.

CS tear gas

CS is a tear gas or chemical  forbidden since 1997.It was used in Iraq , Palestine ,Egypt,and Yemen ...... It caused the death of many innocent people .What is this gas? 




-chlorobenzalmalononitrile (also called o-chlorobenzylidene malononitrile) chemical formula: C₁₀H₅ClN₂is the defining component of a "tear gas" commonly referred to as CS gas.



 
This  chemical reacts with moisture on the skin and in the eyes, causing a burning sensation and the immediate forceful and uncontrollable shutting of the eyes. Effects usually include tears streaming from the eyes, coughing, running nose full of mucus, burning in the nose and throat areas, disorientation, dizziness and restricted breathing. It will also burn the skin where sweaty and or sunburned. In highly concentrated doses it can also induce severe coughing and vomiting. Almost all of the immediate effects wear off in a matter of minutes.As well as creating severe pulmonary damage, CS can also significantly damage the heart and liver.CS emits "very toxic fumes" when heated to decomposition, and at specified concentrations CS gas is an immediate danger to life and health. They also state that those exposed to CS gas should seek medical attention immediately.
In Israel, CS gas was reported to be the cause of death of Jawaher Abu Rahmah on December 31, 2010.^]
It has been noted that the solvent MiBK is itself harmful, and can cause inflammation, dermatitis, burns to the skin and liver damage.

video on types of chemical reactions

Types of chemical reactions -Grade8

Chemical changes are a result of chemical reactions. All chemical reactions involve a change in substances and a change in energy. Neither matter or energy is created or destroyed in a chemical reaction---only changed. There are so many chemical reactions that it is helpful to classify them into 4 general types which include the following:
SYNTHESIS REACTION
In a synthesis reaction two or more simple substances combine to form a more complex substance. Two or more reactants yielding one product is another way to identify a synthesis reaction.
For example, simple hydrogen gas combined with simple oxygen gas can produce a more complex substance-----water!
The chemical equation for this synthesis reaction looks like:

reactant + reactant -------> product
To visualize a synthesis reaction look at the following cartoon:

In the cartoon, the skinny bird (reactant) and the worm (reactant) combine to make one product, a fat bird.

 
DECOMPOSITION REACTION
In a decomposition reaction a more complex substance breaks down into its more simple parts. One reactant yields 2 or more products. Basically, synthesis and decomposition reactions are opposites.
For example, water can be broken down into hydrogen gas and oxygen gas. The chemical equation for this decomposition reaction looks like:

reactant -------> product + product
To visualize a decomposition reaction look at the following cartoon:

In this cartoon the egg (the reactant), which contained the turtle at one time, now has opened and the turtle (product) and egg shell (product) are now two separate substances.
SINGLE REPLACEMENT REACTION
In a single replacement reaction a single uncombined element replaces another in a compound. Two reactants yield two products. For example when zinc combines with hydrochloric acid, the zinc replaces hydrogen. The chemical equation for this single replacement reaction looks like:

reactant + reactant ---------> product + product
To visualize a single replacement reaction look at the following cartoon:


Notice, the guy in the orange shirt steals the date of the other guy. So, a part of one of the reactants trades places and is in a different place among the products.
DOUBLE REPLACEMENT REACTION
In a double replacement reaction parts of two compounds switch places to form two new compounds. Two reactants yield two products. For example when silver nitrate combines with sodium chloride, two new compounds--silver chloride and sodium nitrate are formed because the sodium and silver switched places. The chemical equation for this double replacement reaction looks like:

reactant + reactant ---------> product + product
To visualize a double replacement reaction look at the following cartoon:

ENERGY OF CHEMICAL REACTIONS
Chemical reactions always involve a change in energy. Energy is neither created or destroyed. Energy is absorbed or released in chemical reactions. Chemical reactions can be described as endothermic or exothermic reactions.
Endothermic Reactions
Chemical reactions in which energy is absorbed are endothermic. Energy is required for the reaction to occur. The energy absorbed is often heat energy or electrical energy. Adding electrical energy to metal oxides can separate them into the pure metal and oxygen. Adding electrical energy to sodium chloride can cause the table salt to break into its original sodium and chlorine parts.
Exothermic Reactions
Chemical reactions in which energy is released are exothermic. The energy that is released was originally stored in the chemical bonds of the reactants. Often the heat given off causes the product(s) to feel hot. Any reaction that involves combustion (burning) is an exothermic chemical reaction.
The next two pages include labs for both endothermic and exothermic reactions!

GRADE NINE :Esters

The classic synthesis is the Fischer esterification, which involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent:

RCO₂H + R'OH RCO₂R' + H₂O

 the reaction is slow in the absence of a catalyst. Sulfuric acid is a typical catalyst for this reaction. Many other acids are also used such as polymeric sulfonic acids.

List of ester odorants:

Many esters have distinctive fruit-like odors, which has led to their commonplace use in artificial flavorings and fragrances.

Ester Name	Structure	Odor or occurrence
Allyl hexanoate		pineapple
Benzyl acetate		pear, strawberry, jasmine
Bornyl acetate		pine tree flavor
Butyl butyrate		pineapple
Ethyl acetate		nail polish remover, model paint, model airplane glue
Ethyl butyrate		banana, pineapple, strawberry
Ethyl hexanoate		pineapple, waxy-green banana
Ethyl cinnamate		cinnamon
Ethyl formate		lemon, rum, strawberry
Ethyl heptanoate		apricot, cherry, grape, raspberry
Ethyl isovalerate		apple
Ethyl lactate		butter, cream
Ethyl nonanoate		grape
Ethyl pentanoate		apple
Geranyl acetate		geranium
Geranyl butyrate		cherry
Geranyl pentanoate		apple
Isobutyl acetate		cherry, raspberry, strawberry
Isobutyl formate		raspberry
Isoamyl acetate		pear, banana (flavoring in Pear drops)
Isopropyl acetate		fruity
Linalyl acetate		lavender, sage
Linalyl butyrate		peach
Linalyl formate		apple, peach
Methyl acetate		glue
Methyl anthranilate		grape, jasmine
Methyl benzoate		fruity, ylang ylang, feijoa
Methyl butyrate (methyl butanoate)		pineapple, apple, strawberry
Methyl cinnamate		strawberry
Methyl pentanoate (methyl valerate)		flowery
Methyl phenylacetate		honey
Methyl salicylate (oil of wintergreen)		Modern root beer, wintergreen, Germolene and Ralgex ointments (UK)
Nonyl caprylate		orange
Octyl acetate		fruity-orange
Octyl butyrate		parsnip
Amyl acetate (pentyl acetate)		apple, banana
Pentyl butyrate (amyl butyrate)		apricot, pear, pineapple
Pentyl hexanoate (amyl caproate)		apple, pineapple
Pentyl pentanoate (amyl valerate)		apple
Propyl acetate		pear
Propyl isobutyrate		rum
Terpenyl butyrate		cherry