DIALOG TEACHER AND STUDENT

        DIALOGE TEACHER AND STUDENT

Teacher : good morning!!
Students : good morning mom.
Teacher : okay we will start our lesson. today is we will discuss about oxygen. Nah no one knows what is oxygen?
Rara : I mom, according to the book I read oxygen is a chemical element in a periode table system that has the symbol O and atomic number 8.

Mita : bu oxygen is a class of kalogen elements and can easily react with almost any other element.
Teacher : now the answer from your friends was correct. So oxygen is a chemical element present in this oxygenic periodic table usually in symbols with O and having an atomic number of 8 oxygen is also a cholesterol class element and can easily react with almost any element. Well from the explanation of what you already know what is oxygen.
Student : already bu (answered in unison)

Teacher: now there is a lot of air pollution, who can give an example of air pollution?
Maria : I mom contamination of land because of the amount of garbage piled that is difficult to describe. Pollution of vehicle fumes and factories.
Teacher : is it good that all have understood?
Student : already mom.
Teacher : okay till here our meeting today we continue next week do not forget to learn more about oxygen because tomorrow we will discuss again.

CAUSE AND EFFECT

CORROSION

Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and stopping corrosion.

In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfur. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the original metal, and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases.

Many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances. Corrosion can be concentrated locally to form a pit or crack, or it can extend across a wide area more or less uniformly corroding the surface. Because corrosion is a diffusion-controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the exposed surface, such as passivation and chromate conversion, can increase a material's corrosion resistance. However, some corrosion mechanisms are less visible and less predictable.

Corrosion is the deterioration of a metal as a result of chemical reactions between it and the surrounding environment. Both the type of metal and the environmental conditions, particularly gasses that are in contact with the metal, determine the form and rate of deterioration.

Do All Metals Corrode?

All metals can corrode. Some, like pure iron, corrode quickly. Stainless steel, however, which combines iron and other alloys, is slower to corrode and is therefore used more frequently.

All small group of metals, called the Noble Metals, are much less reactive than others. As a result, they corrode rarely. They are, in fact, the only metals that can be found in nature in their pure form. The Noble Metals, not surprisingly, are often very valuable. They include copper, palladium, silver, platinum, and gold.

Types of Corrosion

There are many different reasons for metal corrosion. Some can be avoided by adding alloys to a pure metal. Others can be prevented by a careful combination of metals or management of the metal's environment. Some of the most common types of corrosion are described below.

1. General Attack Corrosion:

This very common form of corrosion attacks the entire surface of a metal structure. It is caused by chemical or electrochemical reactions. While general attack corrosion can cause a metal to fail, it is also a known and predictable issue. As a result, it is possible to plan for and manage general attack corrosion.

2. Localized Corrosion:

Localized corrosion attacks only portions of a metal structure. There are three types of localized corrosion:

• Pitting -- the creation of small holes in the surface of a metal.
• Crevice corrosion -- corrosion that occurs in stagnant locations such as those found under gaskets.
• Filiform corrosion: corrosion that occurs when water gets under a coating such as paint. weakness.

3. Galvanic Corrosion:

Galvanic corrosion can occur when two different metals are located together in a liquid electrolyte such as salt water. In essence, one metal's molecules are drawn toward the other metal, leading to corrosion in only one of the two metals.

4. Environmental Cracking:

When environmental conditions are stressful enough, some metal can begin to crack, fatigue, or become brittle and weakened. 

Corrosion Prevention

The World Corrosion Organization estimates the global cost of corrosion to be about US$ 2.2 trillion annually, and that a large portion of this - as much as 25% - could be eliminated by applying simple, well-understood prevention techniques. Corrosion prevention should not, however, be considered solely a financial issue, but also one of health and safety. Corroded bridges, buildings, ships, and other metal structures can and do cause injury and death.

An effective prevention system begins in the design stage with a proper understanding of the environmental conditions and metal properties. Engineers work with metallurgical experts to select the proper metal or alloy for each situation. They must also be aware of possible chemical interactions between metals used for surfaces, fittings, and fastenings.

More About Corrosion

Corrosion is a complicated science that requires in-depth knowledge of chemistry, metallurgy, coatings, and environmental stressors. Learn more about corrosion with these related articles:

• Types of Corrosion
• Corrosion Prevention
• Corrosion Control Checklist
• Corrosion Rate Calculator
• Galvanic Corrosion
• Galvanization

VOCABULARY OF CHEMISTRY

VOCABULARY OF CHEMISTRY

acid - There are several ways to define an acid, but they include any chemical that gives off protons or H⁺ in water. Acids have a pH less than 7. They turn the pH indicator phenolphthalein colorless and turn litmus paper red.

acid anhydride - An acid anhydride is an oxide that forms an acid when it is reacted with water. For example, when SO₃^- is added to water, it becomes sulfuric acid, H₂SO₄.

alcohol - An alcohol is any organic molecule that has an -OH group.

aldehyde - An aldehyde is any organic molecule that has a -COH group.

alkali metal - An alkali metal is a metal in Group I of the periodic table. Examples of alkali metals include lithium, sodium, and potassium.

base - A base is a compound that produces OH^- ions or electrons in water or that accepts protons. An example of a common base is sodium hydroxide, NaOH.

beta particle - A beta particle is an electron, although the term is used when the electron is emitted in radioactive decay.

binary compound - A binary compound is one made up of two elements.

buffer - A liquid that resists change in pH when an acid or base is added. A buffer consists of a weak acid and its conjugate base. An example of a buffer is acetic acid and sodium acetate.

calorimetry - Calorimetry is the study of heat flow. Calorimetry may be used to find the heat of reaction of two compounds or the heat of combustion of a compound, for example.

carboxylic acid - A carboxylic acid is an organic molecule containing a -COOH group. An example of a carboxylic acid is acetic acid.

catalyst - A catalyst is a substance that lowers the activation energy of a reaction or speeds it up without being consumed by the reaction.

crystal - A crystal is an ordered, repeating three-dimensional pattern of ions, atoms, or molecules. Most crystals are ionic solids, although other forms of crystals exist.

delocalization - Delocalization is when electrons become free to move all over a molecule, such as when double bonds occur on adjacent atoms in a molecule.

denature - There are two common meanings for this in chemistry. First, it can refer to any process used to make ethanol unfit for consumption (denatured alcohol). Second, denaturing can mean breaking down the three-dimensional structure of a molecule, such as a protein is denatured when exposed to heat.

diffusion - Diffusion is the movement of particles from an area of higher concentration to one of lower concentration.

dilution - Dilution is when a solvent is added to a solution, making it less concentrated.

dissociation - Dissociation is when a chemical reaction breaks a compound into twoor more parts.

For example, NaCl dissociates into Na⁺ and Cl^- in water.

effusion - Effusion is when a gas moves through an opening into a low-pressure container (e.g., is drawn by a vacuum). Effusion occurs more quickly than diffusion because additional molecules aren't in the way.

electrolysis - Electrolysis is using electricity to break the bonds in a compound to break it apart.

electrolyte - An electrolyte is an ionic compound that dissolves in water to produce ions, which can conduct electricity. Strong electrolytes completely dissociate in water, while weak electrolytes only partially dissociate or break apart in water.

endothermic - Endothermic describes a process that absorbs heat. Endothermic reactions feel cold.

endpoint - The endpoint is when a titration is stopped, typically because an indicator has changed color. The endpoint need not be the same as the equivalence point of a titration.

entropy - Entropy is a measure of the disorder or randomness in a system.

enzyme - An enzyme is a protein that acts as a catalyst in a biochemical reaction.

equilibrium - Equilibrium occurs in reversible reactions when the forward rate of the reaction is the same as the reverse rate of the reaction.

equivalence point - The equivalence point is when the solution in a titration is completely neutralized. It is not the same as the endpoint of a titration because the indicator may not change colors precisely when the solution is neutral.

ester - An ester is an organic molecule with a R-CO-OR' function group.

exothermic - Exothermic describes a process that gives off heat.

family - A family is a group of elements sharing similar properties. It is not necessarily the same thing as an element group. For example, the chalcogens or oxygen family consists of some different elements from the nonmetal group.

Kelvin - Kelvin is a unit of temperature. A Kelvin is equal in size to a degree Celsius, although Kelvin starts from absolute zero. Add 273.15 to a Celsius temperature to get the Kelvin value. Kelvin is not reported with a ° symbol. For example, you would simply write 300K not 300°K.

ketone - A ketone is a molecule that contains a R-CO-R' functional group. An example of a common ketone is acetone (dimethyl ketone).

kinetic energy - Kinetic energy is energy of motion. The more an object moves, the more kinetic energy it has.

nucleon - A nucleon is a particle in the nucleus of an atom (proton or neutron).

oxidation number The oxidation number is the apparent charge on an atom. For example, the oxidation number of an oxygen atom is -2.

period - A period is a row (left to right) of the periodic table.

precision - Precision is how repeatable a measurement is. More precise measurements are reported with more significant figures.

pressure - Pressure is force per area.

sublimation - Sublimation is when a solid changes directly into a gas. At atmospheric pressure, dry ice or solid carbon dioxide goes directly into carbon dioxidevapor, never becoming liquid carbon dioxide.

synthesis - Synthesis is making a larger molecule from two or more atoms or smaller molecules.

system - A system includes everything you are evaluating in a situation.

temperature - Temperature is a measure of the average kinetic energy of particles.

valence electron - The valence electrons are the atom's outermost electrons.

volatile - Volatile refers to a substance that has a high vapor pressure.

COMPARE AND CONTRAST

COMPARE AND CONTRAST

Definitions

Compare and contrast essays are multi-paragraph compositions that explain ways in which two (or, very occasionally, more) subjects are similar or different. In these papers, compare means describing similarities between the subjects. When we are comparing Uberman and Catman, we might describe their tragic backstories, their secret double lives, and their fondness for crime fighting. Basically, the comparison tells what they have in common.

Are these 2 things similar and/or different, in at least one meaningful way?

If you want to write a successful compare/contrast essay, you'll need to avoid writing about really obvious differences and similarities.  For example:

• We all know that horses are larger than cats.
• We also know that basketball teams contain less players than football teams.

Tell us something we don't know (or might not notice)!

It would be better to write about how sensitive both horses and cats are to human needs and emotions.  You could also suggest that though both basketball and football require a lot of teamwork, basketball players are expected to be a lot more versatile than football players.

You don't have to be a genius to write an interesting compare/contrast essay--you just have to look at ordinary things in a new wa

HOW TO WRITE COMPARE AND CONTRAST ESSAY

1. Use your brainstorming ideas to fill in your outline. Once you’ve outlined your essay, it should be fairly simple to find evidence for your arguments. Look at the lists and diagrams you generated to help you find the evidence for your comparisons and contrasts.

• If you are having trouble finding evidence to support your argument, go back to your original texts and try the brainstorming process again. It could be that your argument is evolving past where it started, which is good! You just need to go back and look for further evidence.

2. Remember to explain the “why.” A common error many writers make is to let the comparisons and contrasts “speak for themselves,” rather than explaining why it’s helpful or important to put them together. Don’t just provide a list of “ways Topic A and Topic B are similar and different.” In your body paragraphs as well as your conclusion, remind your readers of the significance of your evidence and argument.

• For example, in a body paragraph about the quality of ingredients in frozen vs. homemade pizza, you could close with an assertion like this: “Because you actively control the quality of the ingredients in pizza you make at home, it can be healthier for you than frozen pizza. It can also let you express your imagination. Pineapple and peanut butter pizza? Go for it! Pickles and parmesan? Do it! Using your own ingredients lets you have fun with your food.” This type of comment helps your reader understand why the ability to choose your own ingredients makes homemade pizza better.  

3. Come up with a title. “Essay Number One” may say exactly what the paper is, but it’s not going to win any points for style. A good essay title will preview something about the paper’s argument or topic. Depending on your audience and the situation, you may make a joke or a pun, ask a question, or provide a summary of your main point.

4. Take a break. One of the most common mistakes student writers make is to not give themselves enough time to take a step back from their essays for a day or two. Start early so that you can let your finished draft sit for a day, or at least a few hours. Then, come back to it with fresh eyes. You’ll find it easier to see holes in your logic or organizational flaws if you’ve had time to take a break.

• Reading your essay aloud can also help you find problem spots. Often, when you’re writing you get so used to what you meant to say that you don’t read what you actually said.

Review your essay. Look out for any grammatical errors, confusing phrasing, and repetitive ideas. Look for a balance in your paper: you should provide about the same amount of information about each topic to avoid bias. Here are some things to consider before you turn in your paper:

• Avoid bias. Don't use overly negative or defamatory language to show why a subject is unfavorable; use solid evidence to prove your points instead.
• Avoid first-person pronouns unless told otherwise. In some cases, your teacher may encourage you to use “I” and “you” in your essay. However, if the assignment or your teacher doesn’t mention it, stick with third-person instead, like “one may see” or “people may enjoy.” This is common practice for formal academic essays.
• Proofread! Spelling and punctuation errors happen to everyone, but not catching them can make you seem lazy. Go over your essay carefully, and ask a friend to help if you’re not confident in your own proofreading skills.

EXAMPLE :

I will give you example, Here I will explain the compare and contrast of aluminum and Aurum

 Compare and contrast Al with Au

        Compare:

               1. Conductor

               2. Easy to force

               3. Intangible solid

               4. Corrosion resistant

Contrast:

               b. Aurum

                   1. The atomic number 79 

                   2. Colored metallic yellow

                   3. Strong oxidizing agents

                   4. The amount is a bit in nature

               a. Aluminium

                   1. The atomic number 13

                   2. Colored white

                   3. Strong reductor agent

                   4. The numbers are plentyin nature

                   

     Double Bubble Maps  

               Map to declare compare Al and Au in the center, while the contrast on Al is on the left and Au is on the right.

 

                             

Classification Of Matter

Classification of Matter

Evidence suggests that substances are made up of smaller particles that are ordinarily moving around. Some of those particles of matter can be split into smaller units using fairly strong heat or electricity into smaller rather uniform bits of matter called atoms. Atoms are the building blocks of elements.  Elements are all those substances that have not ever been decomposed or separated into any other substances through chemical reactions, by the application of heat, or by attempting to force an direct electric current through the sample. Atoms in turn have been found to be made up of yet smaller units of matter called electrons, protons, and neutrons. 

      Elements can be arranged into what is called the periodic table of elements based on observed similarities in chemical and physical properties among the different elements. When atoms of two or more elements come together and bond, a compound is formed. The compound formed can later be broken down into the pure substances that originally reacted to form it.

Compounds such as water are composed of smaller units of bonded atoms called molecules. Molecules of a compound are composed of the same proportion of elements as the compound as a whole since they are the smallest units of that compound. For example, every portion of a sample of water is composed of water molecules. Each water molecule contains two hydrogen atoms and one oxygen atom, and so water as a whole has, in a combined state, twice as many hydrogen atoms as oxygen atoms..

Water can still consist of the same molecules, but its physical properties may change. For instance, water at a temperature below 0° Celsius (32° Fahrenheit) is ice, whereas water above the temperature of 100° C (212° F) is a gas, water vapor. When matter changes from one state to another, temperature and pressure may be involved in the process and the density and other physical properties change. The temperature and pressure exerted on a sample of matter determines the resulting form of that the matter takes, whether solid, liquid, or gas.

      Since the properties of compounds and elements are uniform,  they are classified as substances. When two or more substances are mixed together, the result is called a mixture. Mixtures can be classified into two main categories: homogeneous and heterogeneous. A homogeneous mixture is one in which the composition of its constituents are uniformly mixed throughout. A homogeneous mixture in which on substance, the solute, dissolves completely in another substance, the solvent, may also be called a solution. Usually the solvent is a liquid, however the solute can be either a liquid, solid, or a gas. In a homogeneous solution, the particles of solute are spread evenly among the solvent particles and the extremely small particles of solute cannot be separated from the solvent by filtration through filter paper because the spaces between paper fibers are much greater than the size of the solute and solvent particles. Other examples of homogeneous mixtures include sugar water, which is the mixture of sucrose and water, and gasoline, which is a mixture of dozens of compounds.

Example 1: Homogeneous Mixture

Filtered seawater is solution of the compounds of water, salt (sodium chloride), and other compounds.

      A heterogeneous mixture is a nonuniform mixture in which the components separate and the composition varies. Unlike the homogeneous mixture, heterogeneous mixtures can be separated through physical processes. An example of a physical process used is filtration, which can easily separate the sand from the water in a sand-water mixture by using a filter paper. Some more examples of heterogeneous mixtures include salad dressing, rocks, and oil and water mixtures. Heterogeneous mixtures involving at least one fluid are also called suspension mixtures and separate if they are left standing long enough. Consider the idea of mixing oil and water together. Regardless of the amount of time spent shaking the two together, eventually oil and water mixtures will separate with the oil rising to the top of the mixture due to its lower density.

Example 2: Heterogeneous Mixture

    

separation of sand and water             separation of salad dressing                 various mixtures within a rock

Mixtures that fall between a solution and a heterogeneous mixture are called colloidal suspensions (or just colloids). A mixture is considered colloidal if it typically does not spontaneously separate or settle out as time passes and cannot be completely separated by filtering through a typical filter paper.  It turns out that a mixture is colloidal in its behavior if  one or more of its dimensions of length, width, or thickness is in the range of 1-1000 nm. A colloidal mixture can also be recognized by shining a beam of light through the mixture. If the mixture is colloidal, the beam of light will be partially scattered by the suspended nanometer sized particles and can be observed by the viewer. This is known as the Tyndall effect. In the case of the Tyndall effect, some of the light is scattered since the wavelengths of light in the visible range, about 400 nm to 700 nm, are encountering suspended colloidal sized particles of about the same size.  In contrast, if the beam of light were passed through a solution, the observer standing at right angles to the direction of the beam would see no light being reflected from either the solute or solvent formula units that make up the solution because the particles of solute and solvent are so much smaller than the wavelength of the visible light being directed through the solution.

• Solutions: molecules ~0.1-2 nm in size
• Colloids: molecules ~ 2-1000 nm in size
• Suspensions: molecules greater than ~ 1000 nm in size

Example 3: Colloidal Mixtures

Colloidal mixture have components that tend not to settle out.

Milk is a colloid of liquid butterfat globules suspended in water

Figure 2: Flow chart for matter breakdown.

Separation of Mixtures

Most substances are naturally found as mixtures, therefore it is up to the chemist to separate them into their natural components. One way to remove a substance is through the physical property of magnetism. For example, separating a mixture of iron and sulfur could be achieved because pieces of iron would be attracted to a magnet placed into the mixture, removing the iron from the remaining sulfur. Filtration is another way to separate mixtures. Through this process, a solid is separated from a liquid by passing through a fine pored barrier such as filter paper. Sand and water can be separated through this process, in which the sand would be trapped behind the filter paper and the water would strain through. Another example of filtration would be separating coffee grounds from the liquid coffee through filter paper. Distillation is another technique to separate mixtures. By boiling a solution of a non-volatile solid disolved in a liquid in a flask, vapor from the lower boiling point solvent can be driven off from the solution by heat, be condensed back into the liquid phase as it comes in contact with cooler surfaces, and be collected in another container.  Thus a solution such as this may be separated into its original components, with the solvent collected in a separate flask and the solute left behind in the original distillation flask. An example of a solution being separated through distillation would be the distillation of a solution of copper(II) sulfate in water, in which the water would be boiled away and collected and the copper(II) sulfate would remain behind in the disllation flask.

Figure 3: The picture above depicts the equipment needed for a distillation process. The homogeneous mixture starts out in the left flask and is boiled. The vapor then travels down chilled tube on the right and condenses back into a liquid and drips into the flask.

States of Matter

Everything that is familiar to us in our daily lives - from the land we walk on, to the water we drink and the air we breathe - is based upon the states of matter called gases, liquids, and solids.

Solids

When the temperature of a liquid is lowered to the freezing point of the substance (for water the freezing point is 0^oC), the movement of the particles slows with the spacing between the particles changing until the attractions between the particles lock the particles into a solid form. At the freezing point, the particles are closely packed together and tend to block the motions of each other. The attractions between the particles hold the particles tightly together so that the entire ensemble of particles takes on a fixed shape. The volume of the solid is constant and the shape of a solid is constant unless deformed by a sufficiently strong external force.  (Solids are thus unlike liquids whose particles are slightly less attracted to one another because the particles of a liquid are a bit further apart than those in the corresponding solid form of the same substance.)  In a solid the particles remain in a relatively fixed positions but continue to vibrate.  The vibrating particles in a solid do not completely stop moving and can slowly move into any voids that exist within the solid.

            

Figure 4: The diagram on the left represents a solid whose constituent particles are arranged in an orderly array, a crystal lattice. The image on the right is a ice cube. It has changed from liquid into a solid as a result of absorbing energy from its warmer environment. 

Liquids

When the temperature of a sample increases above the melting point of a solid, that sample can be found in the liquid state of matter. The particles in the liquid state are much closer together than those in the gaseous state, and still have a quite an attraction for each other as is apparent when droplets of liquid form. In this state, the weak attractive forces within the liquid are unable to hold the particles into a mass with a definite shape. Thus a liquid's shape takes on the shape of any particular container that holds it.  A liquid has a definite volume but not a definite shape. Compared to to the gaseous state there is less freedom of particle movement in the liquid state since the moving particles frequently are colliding with one another, and slip and slide over one another as a result of the attractive forces that still exist between the particles, and hold the particles of the liquid loosely together.  At a given temperature the volume of the liquid is constant and its volume typically only varies slightly with changes in temperature.

     

Figure 5: The diagram on the left represents a container partially filled with a liquid. The image on the right is of water being poured out of a glass. This shows that liquid water has no particular shape of its own.

Gases

In the gas phase, matter does not have a fixed volume or shape. This occurs because the molecules are widely separated with the spaces between the particles typically around ten times further apart in all three spatial directions, making the gas around 1000 times less dense than the corresponding liquid phase at the same temperature. (A phase is a uniform portion of mater.) As the temperature of a gas is increased, the particles to separate further from each other and move at faster speeds.  The particles in a gas move in a rather random and independent fashion, bouncing off each other and the walls of the container.  Being so far apart from one another, the particles of a real gas only weakly attract each other such that the gas has no ability to have a shape of its own. The extremely weak forces acting between the particles in a gas and the greater amount of space for the particles to move in results in almost independent motion of the moving, colliding particles. The particles freely range within any container in which they are put, filling its entire volume with the net result that the sides of the container determine the shape and volume of gas. If the container has an opening, the particles heading in the direction of the opening will escape with the result that the gas as a whole slowly flows out of the container.

       

Figure 6: The image on the left represents an enclosed container filled with gas. The images are meant to suggest that the gas particles in the container are moving freely and randomly in myriad directions.The image on the right shows condensing water forming from the water vapor that escaped from the container.