DIALOGE OF TEACHER AND STUDENT ABOUT CHEMISTRY

  DIALOGE OF TEACHER AND STUDENT ABOUT CHEMISTRY LESSON.

Time Chemical Class

Teacher   : Assalamualaikum my student
Students  : Waalaikumsalam miss
Teacher   : is ready to study chemistry today? Is today's material already learned at home?
Students  : already a book
Teacher   : well today we will discuss about redox reactions. If you have studied at home. What is a redox reaction?
Student   : I am miss, redox reaction comes from the word reduction and oxidation. Reduction is a chemical reaction involving electron capture, release of O2 and a decrease in oxidation number. While oxidation is a chemical reaction involving the release of electrons, the release of hydrogen, the binding of oxygen and the raising of oxidation numbers.
Teacher  : very well described by your friend, in redox reaction there are three concepts, that is related to oxygen, with electrons and with biloks.
Student   : miss, I want to ask how the redox example relates to electrons? 
Teacher  : okay, in relation to the reduction electrons happen to capture or receive electrons and on the oxidation of electrons.
For example Mg²⁺ + 2e^-  --> Mg
Example above what is the reduction of oxidation?
Student   : miss reduction, because Mg receives electrons.
Teacher  : good, for biloks we have to know the rules of biloks first.
1. Free element, biloks = 0
2. The oxygen atom in the oxidation compound = -2
3. Atoms of hydrogen biloks = 1
4. Atoms of ions / compounds of oxidized ions = groups
5. The element of group IA, IIA, IIIA biloks = group 

Teacher  : who can determine the oxidation state of MnO₂ ?
Student   : I'm a miss,
Teacher  : okay do it in front
Student  : MnO2
2 x (-2) + 4 = 0
So the answer =  +4

Teacher  : good job. So the oxidation reaction takes place simultaneously with the reduction reaction and called the redox reaction. Substances undergoing oxidation reactions are called reducing agents. While substances that undergo a reduction reaction called oxidizer (peoksidasi). Do you understand?
Students  : understand the book
Teacher  : well enough for our lesson today, see you next week. 
Wassalamu alaikum warahmatullahi wabarakatuh
Student: waalaikumsalam miss.

DOUBLE BUBBLE MAPS

Comparison between helium and fluorescent elements

GAS NOBLE ELEMENTS
Helium is used as a cooling medium for the Large Hadron Collider (LHC), and the superconducting magnets in MRI scanners and NMR spectrometers. It is also used to keep satellite instruments cool and was used to cool the liquid oxygen and hydrogen that powered the Apollo space vehicles.

Because of its low density helium is often used to fill decorative balloons, weather balloons and airships. Hydrogen was once used to fill balloons but it is dangerously reactive.

Because it is very unreactive, helium is used to provide an inert protective atmosphere for making fibre optics and semiconductors, and for arc welding. Helium is also used to detect leaks, such as in car air-conditioning systems, and because it diffuses quickly it is used to inflate car airbags after impact.

A mixture of 80% helium and 20% oxygen is used as an artificial atmosphere for deep-sea divers and others working under pressurised conditions.

Helium-neon gas lasers are used to scan barcodes in supermarket checkouts. A new use for helium is a helium-ion microscope that gives better image resolution than a scanning electron microscope.

 After hydrogen, helium is the second most abundant element in the universe. It is present in all stars. It was, and is still being, formed from alpha-particle decay of radioactive elements in the Earth. Some of the helium formed escapes into the atmosphere, which contains about 5 parts per million by volume. This is a dynamic balance, with the low-density helium continually escaping to outer space.

It is uneconomical to extract helium from the air. The major source is natural gas, which can contain up to 7% helium.

HELIUM
Helium → Helios (Yunani) : matahari
Helium = 0,00052 %
Electron configuration 1s²

Helium (He) is a chemical element that is colorless, odorless, tasteless, non-toxic, almost inert, monatomic, and is the first element in the noble gas series in the periodic table and has atomic number 2. On Mars only a little Helium. The boiling point and melting point are the lowest of the other elements and it exists only in gaseous form except in "extreme" conditions. Extreme conditions are also needed to create a small amount of helium compounds, all of which are unstable at standard temperature and pressure. Helium has a rare second stable isotope called helium-3. The properties of the fluid of the helium-4 varieties; Helium I and helium II; It is important for researchers who study quantum mechanics (especially in superfluidity phenomena) and for those looking for effects near absolute zero temperatures possessed by objects (such as superconductivity).
Helium is the second largest and lightest element in the universe and one of the elements created during Big Bang nucleosynthesis. In the modern Jagad Raya almost all new helium was created in the process of nuclear fusion of hydrogen inside the star. On Earth, this element was created by radioactive decay from heavier elements (alpha particles are helium nuclei). After its creation, some of it is contained in air (natural gas) in concentrations up to 7% by volume. Helium is purified from the air by a low temperature separation process called fractional distillation.

NEON

Neon → Neos (Yunani) : baru

Neon = 0,00182 %

Electron configuration [He] 2s² 2p⁶

Neon (Ne) adalah suatu unsur kimia dalam tabel periodik yang memiliki lambang Ne dan nomor atom 10. Neon termasuk kelompok gas mulia yang tak berwarna dan lembam (inert). Unsur Ne ditemukan pertama kali oleh William Ramsay dan Morris William Travers tahun 1898 di Inggris.

A. Helium

• As an air balloon filler. 
• As a mixture of oxygen in the diver tube. 
• Helium in the form of liquid can also be used as a coolant because it has a very steam point of red.

B. Neon

• Neon is usually used to fill fluorescent lamps. 
• Neon can be used to share things like high-voltage indicators, refrigerants, lightning rods, and television tubes. 
• Liquid fluid is a refrigerant in the refrigenerator for low temperatures. 
• Neon can also be used to mark the plane.
  

Show Cause and Effect Chemical Reaction

CHEMICAL REACTION

Chemical reactions are a process of changing one or more substances into one or more different substances. The same reaction. The chemical reaction equation of the reacting formula and the reaction products corresponding to the arrows. The phases of substances which are resistant to the symbols s for solid (solid), g for gas (gas), l for liquid (liquid), and aq for soluble substances (aquaeus).

Chemical reactions can be observed from changes, such as changes in color, changes in shape, and the main thing is the change of substances accompanied by changes in energy in the form of heat. Chemical reactions are the key to chemistry. By reacting a substance means we turn the substance into another substance, both the nature and the form. Thus, if we expect a substance that has certain characteristics, we must try to find raw materials that when reacted with certain substances produce substances that we expect

In a reaction applies the law of conservation of mass, the mass of substances equal to the mass of the reaction products. For that the set of reactions must be the same, ie the number of atoms on the left should be equal to the number of atoms on the right. To create a shared process.

Various kinds of chemical reactions

By knowing some properties or types of reactions, we can understand the chemical reactions more easily. Generally, chemical reactions are classified by type as follows:
1. Reaction of merging

2. Decomposition reaction
3. Reaction of change (single exchange reaction)
4. Metathesis reaction (multiple exchange reaction) 

1. Merger Reaction 
The merging reaction is a reaction in which two substances merge to form a third substance. The simplest case is when two elements react to form a compound. For example the sodium metal reacts with chlorine gas to form sodium chloride. The equation of the reaction:

2Na(s) +Cl₂(g) → 2NaCl(s)

Other examples are the reaction between white phosphor and chlorine gas. In limited chlorine amounts, phosphorus reacts to form phosphorus trichloride, PCl3, a colorless liquid.

P₄(s) + 6Cl₂(g) → 4PCl₃(l)

If the available heat is excessive, the phosphorus compound produced is phosphorus pentachloride, PCl5, a white solid.

P₄(s) + 10Cl₂(g) → 4PCl₅(s)

Other merging reactions involve the compound as reagents. For example: phosphorus trichloride reacts with chlorine gas to form phosphorus pentachloride. The equation of the reaction:

Cl₃(l) + Cl₂(g) → PCl₅(s) 

2. Decomposition Reactions

The decomposition reaction is a reaction when a single compound reacts to form two or more substances. Usually this reaction requires a rise in temperature for the decomposable compound by increasing the temperature eg KclO₃. This compound when heated will decompose into KCl and oxygen gas. The equation of the reaction:

KClO₃(s) → 2KCl(s) + 3O₂(g)

The decomposition reaction is commonly applied in limestone processing in the area of ​​West Java cipatat. Limestone, CaCO₃ extracts that can be used as building materials need to be further processed into tohor, CaO. The processing of limestone is done by way of roasting limestone in the stove. The chemical equations are:

CaCO₃(s) → CaO(s) + CO₂(g) 

3. Exchange Reactions

Reaction of a change or also called a single exchange reaction is the reaction in which an element reacts with a compound to replace the element contained in the compound. For example, if the copper metal plate is immersed in a silver nitrate solution, a silver metal crystalline is produced. The equation of the reaction is:

Cu(s) + 2AgNO₃(aq) → 2Ag(s) + Cu(NO₃)₂(aq)

Copper replaces the silver contained in silver nitrate, producing a solution of copper nitrate and silver metal.

If the logamseng plate is immersed in a blue copper sulphate solution, then on the surface of the zinc metal there will be a red copper deposit, and the blue color of the solution slowly fades. This shows that zinc reacts with copper sulfate to produce copper metal and a colorless zinc sulfate solution. 

 4. Metathesis reaction

The reaction of metathesis or a dual exchange reaction is a reaction involving the exchange of parts of the reactant. If the reagents are ionic compounds in solution form, the exchange portion is the cation and anion of the compound. For example a colorless potassium iodide solution is mixed with lead (II) nitrate solution which is also colorless. The ions in the solution react to form a yellow precipitate of the lead (II) iodide compound. The equation of the reaction:

2KI(aq) +Pb(NO₃)₂(aq) → 2KNO₃(aq) + PbI₂(s)

Iodide ions in the potassium iodide solution exchange with nitrate ions from lead (II) nitrate solution, yields a colorless potassium nitrate solution and a yellow i (y) iodide lead solid, as PbI2.

The reaction of acids and bases that produce salt, is also considered a metathesis reaction. For example the reaction between hydrochloric acid, HCl (aq) and sodium hydroxide (aq), the equation of the reaction:

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

The acid-base reaction is also called the neutralization reaction, because it occurs the inclusion of the H ⁺ charge by the electrically neutral (H₂O) water-formed OH. The salt of NaCl formed remains in solution as its ions. 

5. Burning reaction

The reactions we consider so far can be characterized as reactor reactions of atoms. However, we need to add another kind of reaction that is the combustion reaction, which is characterized by the fact that one of its reactants is oxygen. The combustion reaction is the reaction of a substance with oxygen, usually reacting rapidly with the release of heat forming a flame.

If carbon compounds are burned in oxygen or air will form carbon dioxide and water vapor when the combustion is complete. However, when incomplete combustion (lack of oxygen) will form carbon monoxide gas, or may be formed carbon black (soot). Some examples of combustion of carbon compounds:

CH₄(g) + 2O₂(g) → CO­­₂(g) + 2H₂O(g)

2CH₃OH(l) + 3O₂(g) → 2CO₂(g)  + 4H₂O(g)

C₄H₁₀(g) + 13O₂(g) → 8CO₂(g) + 10H₂O(g)

Ironing, although not commonly considered as combustion, is essentially a combustion reaction, because there is a reaction between iron and oxygen accompanied by the release of energy. The iron-cellification reactions are in fact very complex involving water molecules, but we can write the karate in the form of a net reaction, which is as follows:

4Fe(s) + 3O₂(g) + nH₂O(l) → 2Fe₂O₃.nH₂O(s)

Some examples of chemical reactions

1. The reaction containing the precipitate

A. PbCr₂O + K₂ (NO₃)₂ →Pb (NO₃)₂ + K₂Cr₃O₇

B. PbOH + Na (NO₃)₂→Pb (NO₃)₂ + Na OH

From the reaction, both produce white precipitate. It is caused by the solution of Pb (NO₃)₂  which is the precipitate of this solution, because Pb (NO₃)  has solid properties.

2. Reactions that produce discoloration

A. K₂Cr₂O7 + NaOH → K₂OH + NaCr₂0₇

B. K₂Cr₂O₇ + HCl→K₂Cl + HCr₂O₇

In K2Cr2O7 solution which initially is orange and NaOH color is white, then after mixing will produce yellow color. Likewise with K2Cr204 solution is yellow, after mixed with white HCl will produce orange color.
 
3. The reaction that produces gas

Zn + 2 HCl → ZnCl₂ + H₂

The gas-generating reaction can occur when the zinc metal plate (Zn) is mixed with HCl solution.
From the above examples, it can be concluded that the chemical reactions can be seen from the changes that occur due to mixing two substances such as sediment formed, discoloration, and produce gas.

Some of these changes are the formation of sediment, the occurrence of color changes, the formation of gas, and the presence of temperature changes. 


1. Chemical Reactions Produce Sludge

Around us there are many chemical reactions that can produce sediment. Reactions that include examples of chemical reactions that produce precipitates include:

• Occurrence of carbonate compounds at the bottom of the pan when boiling water.

• When the lime water is blown, there will be a reaction between lime water and the carbon dioxide from the breath. The occurrence of the reaction can be observed the formation of white calcium carbonate (CaCO3) that settles on the bottom of the glass if left for a while.

• Precipitation by chemical reactions has long been used for water purification processes. The muddy well water mixed with mud can be clarified with the addition of alum. Tawas will tie the particles of mud particles to clot and eventually settle.

  2. Chemical Reactions Produce Color ChangesApples

 

 that are cut and left for a while, over time will be Turn brown. This color change indicates that the chemicals in apples have reacted with oxygen in the air. The reaction between the starch starch solution with iodine tintur can be known from the color change that occurs. Color clear starch solution, brown iodine. If both are mixed will form a blue color. If added vitamin C then iodine will react with vitamin C to form other chemicals that are colorless. So the occurrence of chemical reactions can be known from the color changes that occur. Household tools made of metal, these objects will gradually change color. The tool of iron will rust so that it becomes black, copper tools will change color to greenish, the tool from silver will change color to black. The color change indicates that there has been a chemical reaction to the devices. The color of the clothes we wear will fade as it reacts with the chemicals contained in the detergent. 

 3. Chemical Reactions Produce Gas

 

In everyday life, many of us encounter marked chemical reactions with the formation of gas. When the carbide is mixed with water, it will produce carbide gas. This gas is generally used for purposes metal welding. In addition, carbide gas can also used to speed up the ripening of the fruit. When making a cake, into the dough is added baking soda. As the dough is heated, baking soda will break down producing carbon dioxide gas. Gas is what causes the cake to expand.

  4. Chemical Reactions Produce Temperature Changes

A firecracker explosion is the result of a chemical reaction. All reactions always involving energy, some reactions absorb energy and some are releasing energy. The energy that accompanies the chemical reaction is heat, light, sound, or electrical energy. A chemical reaction that produces energy is called an exothermic reaction. If the energy is hot, it can tell by measuring its temperature rise. The combustion reaction is an example of an exothermic reaction.when reacting with water, we can feel the increase the temperature on the glass wall where the reaction is performed. Large temperature rise can measured with a thermometer. A chemical reaction that requires energy called endothermic reactions. For example, a reaction to the photosynthesis process.