Cause And Effect Chemical Reactions
Because the word and effect are used to express a chemical reaction which, when reacted, results in a cause or cause arising from the reaction occurring, therefore the word arena an effect is used to express the sentence
Every single living thing on Earth depends on chemical reactions — from the largest mammal, the blue whale, right down to the smallest insects. In plants, chemical reactions transform carbon dioxide and water into sugars and other nutrients such as proteins and starch. The burning of fuels to generate electricity, operate industry and transportation, and keep our homes at a comfortable temperature is a chemical reaction, as is the formation of crystals in a retort. So what are chemical reactions?
Because the word and effect are used to express a chemical reaction which, when reacted, results in a cause or cause arising from the reaction occurring, therefore the word arena an effect is used to express the sentenceEvery single living thing on Earth depends on chemical reactions — from the largest mammal, the blue whale, right down to the smallest insects. In plants, chemical reactions transform carbon dioxide and water into sugars and other nutrients such as proteins and starch. The burning of fuels to generate electricity, operate industry and transportation, and keep our homes at a comfortable temperature is a chemical reaction, as is the formation of crystals in a retort. So what are chemical reactions?
Chemical reactions take place when the bonds between atoms are broken and new bonds are formed, creating a new arrangement of atoms and at least one new substance. As the new substance is formed, observable changes take place a change in temperature or colour, the formation of a visible gas or new solid, or perhaps even just an odour.
Reactants and products
The new substances that are formed during a chemical are called the products. The original substances are called the reactants. For example, when hydrogen gas is added to oxygen gas and ignited, the new substance water is formed. The reactants are hydrogen and oxygen. The product is water. The bonds between the hydrogen atoms and oxygen atoms are broken and new bonds are formed between oxygen and hydrogen, as shown below. Notice that the hydrogen and oxygen atoms that were present in the reactants are also present in the product. There is no gain or loss of atoms. They have simply been rearranged.
Matter and Energy: Chemical Reactions and Energy
When fuels such as petrol are burned in motor vehicles, energy is released and used to keep the vehicle in motion. Burning is a chemical reaction in which fuel reacts with oxygen, producing carbon
dioxide, water and several other products. The energy released comes from the rearrangement of atoms. There is less energy stored in the chemical bonds in the products than there was in the reactants. Chemical reactions that release energy are called exothermic reactions. Chemical reactions in which energy is absorbed from the surroundings are called endothermic reactions. There is more energy ‘stored’ in the chemical bonds of the products than there was in the reactants.
dioxide, water and several other products. The energy released comes from the rearrangement of atoms. There is less energy stored in the chemical bonds in the products than there was in the reactants. Chemical reactions that release energy are called exothermic reactions. Chemical reactions in which energy is absorbed from the surroundings are called endothermic reactions. There is more energy ‘stored’ in the chemical bonds of the products than there was in the reactants.
Hot stuff
Portable hand warmers, commonly used by skiers and campers, become hot when shaken due to an
exothermic chemical reaction in which energy is released to the surroundings. One type of hand
warmer contains iron, water, salt and sawdust. When the contents of the packet are shaken quickly, the powdered iron reacts with oxygen to form iron oxide. During this chemical reaction, some of the chemical energy of the substances is transformed into heat energy which is transferred to the hands, increasing their temperature. We can show this chemical reaction with a word equation:
exothermic chemical reaction in which energy is released to the surroundings. One type of hand
warmer contains iron, water, salt and sawdust. When the contents of the packet are shaken quickly, the powdered iron reacts with oxygen to form iron oxide. During this chemical reaction, some of the chemical energy of the substances is transformed into heat energy which is transferred to the hands, increasing their temperature. We can show this chemical reaction with a word equation:
iron + oxygen → iron oxide
As cold as ice
Athletes use instant icepacks to treat injuries. The icepack may consist of a plastic bag containing ammonium nitrate or ammonium chloride powder and an inner bag of water. Squeezing the bag breaks the weaker inner bag and immediately causes the powder to dissolve in the water. The chemical process that takes place absorbs energy from the injured area, thus lowering its temperature. It is therefore an endothermic chemical process. We can describe this chemical
process with a word equation:
process with a word equation:
ammonium chloride + water → ammonium chloride in solution
What is a chemical reaction?
A chemical reaction is the change of a substance into a new one that has a different chemical identity.
How can I tell if a chemical reaction is occurring?
A chemical reaction is usually accompanied by easily observed physical effects, such as the emission of heat and light, the formation of a precipitate, the evolution of gas, or a color change. Absolute confirmation of a chemical change can only be validated by chemical analysis of the products! There are many different types of chemical reactions. Chemists have classified the many different reactions into general categories. The chemical reactions we will explore are a representation of the types of reactions found in each group. There is a general description of the main reaction types and specific examples provided in the selection boxes.
1. Synthesis Reaction (Combination Reaction)
In a synthesis reaction, two or more substances combine to form a new compound. This type ofreaction is represented by the following equation.
A + B → AB
A and B represent the reacting
elements or compounds while AB represents a compound as the product.
The
following examples are representative of synthesis reactions.
Formation
of Aluminum Bromide: When Al is placed on the
surface of liquid Br2 an exothermic reaction occurs. The Al is
oxidized to Al3+ by the Br2, which is reduced to Br - ions. The ionic product,
AlBr3, can be observed on the watch glass after the reaction.
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Formation
of Sodium Chloride: Molten sodium burns when
it is put into a container of chlorine gas. In the reaction a sodium ion
loses an electron to form a sodium cation and a chlorine atom simultaneously
gains an electron to form a chloride anion. The product of the reaction is
the ionic compound sodium chloride, which is the white solid observed.
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Formation
of Zinc Oxide: Oxidation is a loss of
electrons and reduction is a gain of electrons. The oxidation of metallic Zn
by O2 to form ZnO(s) is illustrated at the molecular
level. The transfer of electrons from Zn to O2 is shown. Atoms can
be observed to change as they are oxidized or reduced, respectively to their
ionic forms.
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Formation
of Sodium Hydroxide and Potassium Hydroxide:
When
a small piece of Na is added to a solution containing an indicator, evidence
of the reaction can be observed by the change in the color of the solution as
NaOH is formed, by the melting of the Na and by the movement of the Na caused
by formation of hydrogen gas. K is more reactive than Na as demonstrated by
its reaction with water. This reaction produces enough heat to ignite the H2
produced.
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2. Single-Replacement Reaction
In a single-replacement reaction (displacement reaction) one element replaces a similar element in the compound. Single-replacement reactions can be represented by the following equations.
AB + C → AC + B
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Thermite
Reaction: In the thermite reaction,
Al reduces Fe2O3 to Fe in an extremely exothermic
reaction in which Al is oxidized to Al2O3. The reaction
produces enough heat to melt the iron. Because of the extreme heat produced
in the thermite reaction, it is used industrially to weld iron.
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Reduction
of CuO: When black carbon and
black copper oxide are heated together the Cu2+ ions are reduced
to metallic Cu and a gas is evolved. When the gas is collected in Ca(OH)2
a white precipitate of CaCO3 is formed. The reaction which occurs
involves the reduction of Cu2+ ions by carbon which is oxidized to
CO2.
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Formation
of Silver Crystals: When a copper wire is
placed in a solution of AgNO3, the Cu reduces Ag+ to
metallic Ag. At the same time, Cu is oxidized to Cu2+. As the
reaction progresses Ag crystals can be seen to form on the Cu wire and the
solution becomes blue as a result of the formation of Cu2+ ions.
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Formation
of Tin Crystals: Oxidation-reduction
chemistry of Sn and Zn. When acidified Sn(II)Cl2 is added to a
beaker containing a piece of Zn, some of the Sn2+ reacts with H+
in the solution to produce H2 gas. Immediate changes can also be
observed on the surface of the Zn as it quickly becomes coated with Sn
crystals. After the reaction has progressed for a time needles of Sn can be
observed on the surface of the Zn.
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3. Double-Replacement Reaction
In a double-replacement reaction, the ions of two compounds exchange places in an aqueous solution to form two new compounds. A double-replacement reaction can be represented by the following equation.
AB + CD → AC + BD
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This
marble statue has been eroded by acid rain. Marble is a material having CaCO3
as its primary component. Acids react with and dissolve the marble. The acid comes from sulfur dioxide in the
atmosphere combining with water to form sulfurous acid.
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An
aqueous solution of Potassium Iodide is added to an aqueous solution of Lead
(II) Nitrate forming lead (II) iodide.
The formation of a precipitate occurs when the cations of one reactant
combines with the anions of the other reactant to form an insoluble or
slightly insoluble compound.
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An
aqueous solution of Sodium Chloride is added to an aqueous solution of Silver
Nitrate forming silver chloride.
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4. Decomposition Reaction
In a decomposition reaction, single compound undergoes a reaction that produces two or more simpler substances. A decomposition reaction can be represented by the following equation.
AB → A + B
Electrolysis
of Water: When a direct current is passed through
water it decomposes to form oxygen and hydrogen. The volume of hydrogen gas
produced at the negative electrode is twice the volume of the oxygen gas
formed at the positive electrode. This indicates that water contains twice as
many hydrogen atoms as oxygen atoms, which is an illustration of the law of
constant composition.
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Decomposition of Nitrogen
Triiodide:
Nitrogen triiodide is extremely unstable when it is dry. Touching it with a
feather causes it to decompose explosively. The explosion occurs as chemical
energy is released by the decomposition of nitrogen triiodide to N2
and I2. Violet iodine vapor can be observed after the explosion.
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3. Combustion Reaction
In a combustion reaction, a substance combines with oxygen, releasing a large amount of energy in the form of light and heat. For organic compounds, such as hydrocarbons, the products of the combustion reaction are carbon dioxide and water.
CH4 + 2
O2 → CO2 + 2
H2O
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The
combustion of hydrogen yields water vapor as a reaction product. Three balloons of hydrogen and one balloon
mixed with hydrogen and oxygen form an explosive mixture
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Reactions
with Oxygen. Magnesium, steel wool, white phosphorous, and sulfur are burned
in oxygen. The resulting reactions are combination reactions in which two
substances react to form one product. The products formed in these reactions
are MgO, Fe2O3, P4O10 and SO2.
All of these combustion reactions are very exothermic.
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The
combustion of yellow phosphorus occurs in an oxygen atmosphere. The
main product of this reaction is phosphorus pentoxide.
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Source :
http://www.ric.edu/faculty/ptiskus/reactions/
http://www.wiley.com/legacy/Australia/PageProofs/SQ9_AC_VIC/c07Chemicalreactions_WEB.pdf
http://www.ric.edu/faculty/ptiskus/reactions/
http://www.wiley.com/legacy/Australia/PageProofs/SQ9_AC_VIC/c07Chemicalreactions_WEB.pdf
What happen if activation energy in chemical reaction less or more ? Can you explain .
BalasHapusthks for your question al i will to try to be answer
HapusAll molecules possess a certain minimum amount of energy. The energy can be in the form of kinetic energy or potential energy. When molecules collide, the kinetic energy of the molecules can be used to stretch, bend, and ultimately break bonds, leading to chemical reactions. If molecules move too slowly with little kinetic energy, or collide with improper orientation, they do not react and simply bounce off each other. However, if the molecules are moving fast enough with a proper collision orientation, such that the kinetic energy upon collision is greater than the minimum energy barrier, then a reaction occurs. The minimum energy requirement that must be met for a chemical reaction to occur is called the activation energy, Ea.
Rate of reaction is the amount of reactions per unit of time. In order for a reaction to take place the reactants need to traveling at a certain speed when they collide and orientation and a whole bunch of other factors.
If the activation energy of a reaction is high, there are less molecules traveling with that amount of kinetic energy to initiate the reaction, so the rate is less.
How effective if someone is exposed to dangerous chemicals?
BalasHapuspeople respond to chemical exposure in different ways. Some people may be exposed to a chemical and not get sick. Other people may be more sensitive to chemicals and get sick more rapidly or have more severe reactions than others. Certain variables play a role in a person's susceptibility to exposure and adverse health effects such as age, gender, genetics, pregnancy or other health conditions.
HapusFor the fetus, child, and adolescent, the adverse health effects from exposure to chemicals can be much greater than for adults. The factors that affect their susceptibility include their stage of development and level of activity in the environment. The fetus is the most susceptible because their developing organs may be permanently damaged. Similarly, children, especially from one to six years of age, are also in a stage of rapid development. During this period, children may take more chemical into their bodies due to body chemistry, level of activity, and relative small body size. As children develop, chemicals introduced into the body can alter many processes essential for proper cell development. As a result, changes can, for example, cause organs within the body to be altered, impairing proper development to a mature organ. Adolescents may share in the risk due to their increased physical activity and curiosity of the world around them. For more information, see Children's Health Protection.
The human body has the ability to tolerate certain amounts of chemicals and the ability to excrete chemicals from the body. Once a person is exposed to a chemical, it may enter the blood stream, and eventually reach the liver. The liver attempts to detoxify harmful chemicals in the body by converting them to less toxic ones or ones that could be used by the body. The body naturally attempts to eliminate substances that are harmful or are not used. The kidneys filter substances out of the blood and excrete them in urine. Also, chemicals are removed from the body in feces, sweat and exhalation. However, the body may not be able to remove all the chemicals. The amount, type, and length of time you are exposed to harmful substances will determine if you are at risk for adverse health effects.
Therefore, the state and federal governments have determined health-based comparison values for contaminants that when exceeded, exposure may result in an excessive health risk. The chart below contains levels used by agencies to determine if doses of chemicals may be harmful to human health.
How chemical reactions can accur and give axamples of chemical reactions in daily life?
BalasHapusChemistry happens in the world around you, not just in a lab. Matter interacts to form new products through a process called a chemical reaction or chemical change. Every time you cook or clean, it's chemistry in action. Your body lives and grows thanks to chemical reactions. There are reactions when you take medications, light a match, and take a breath. Here's a look at 10 chemical reactions in everyday life. It's only a small sampling since you see and experience hundreds of thousands of reactions each day.
Hapusfor examples :
1. Photosynthesis Is a Reaction To Make Food
Plants apply a chemical reaction called photosynthesis to convert carbon dioxide and water into food (glucose) and oxygen. It's one of the most common everyday chemical reactions and also one of the most important since this is how plants produce food for themselves and animals and convert carbon dioxide into oxygen.
6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
2. Aerobic Cellular Respiration Is a Reaction With Oxygen
Aerobic cellular respiration is the opposite process of photosynthesis in that energy molecules are combined with the oxygen we breathe to release energy needed by our cells plus carbon dioxide and water. Energy used by cells is chemical energy in the form of ATP.
Here is the overall equation for aerobic cellular respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (36 ATPs)
3. Anaerobic Respiration - Everyday Chemical Reactions
In contrast to aerobic respiration, anaerobic respiration describes a set of chemical reactions that allow cells to gain energy from complex molecules without oxygen. Your muscles cells perform anaerobic respiration whenever you exhaust the oxygen being delivered to them, such as during intense or prolonged exercise. Anaerobic respiration by yeast and bacteria is harnessed for fermentation, to produce ethanol, carbon dioxide, and other chemicals that make cheese, wine, beer, yogurt, bread, and many other common products.
The overall chemical equation for one form of anaerobic respiration is:
C6H12O6 → 2C2H5OH + 2CO2 + energy
Every time you strike a match, burn a candle, build a fire, or light a grill, you see the combustion reaction. Combustion combines energetic molecules with oxygen to produce carbon dioxide and water.
For example, the combustion reaction of propane, found in gas grills and some fireplaces, is:
C3H8 + 5O2 → 4H2O + 3CO2 + energy
4. Combustion Is a Type of Chemical Reaction
Every time you strike a match, burn a candle, build a fire, or light a grill, you see the combustion reaction. Combustion combines energetic molecules with oxygen to produce carbon dioxide and water.
For example, the combustion reaction of propane, found in gas grills and some fireplaces, is:
C3H8 + 5O2 → 4H2O + 3CO2 + energy
and many more
hi rini , could you give an example one or two reaction where the reaction is Involve oxygen or hidrogen , thanks
BalasHapusHydrogen and oxygen react to form water but you just cannot write the equation as 2H + 1O because hydrogen and oxygen do not exist as single atoms but rather as the molecules H2 and O2. The equation should show these molecules as the reactants on the left side of the reaction arrow.
HapusH2 + O2 => H2O
In this reaction there are 2 hydrogen atoms on the left side of the reaction arrow and 2 hydrogen atoms on the right side of the reaction arrow so the reaction is balanced with respect to the hydrogen. However there are 2 oxygen atoms on the left and only one on the right. To correct this imbalance, place a 2 in front of the H2O. Now the oxygen atoms are balanced with 2 on the left and two on the right. The hydrogen atoms are no longer balanced because there are 4 hydrogen atoms on the right and only 2 on the left.
H2 + O2 => 2 H2O
The equation will finally be balanced when the one molecule of H2 on the left is changed to 2 molecules.
2 H2 + O2 => 2 H2O
This equation is now a balanced equation. It tells us that 2 molecules of hydrogen react with 1 molecule of oxygen to form 2 molecules of water.
for the example :
1. 4Fe(s) + 3O2(g) → 2Fe2O3(s)
2. 2Mg(s) + O2(g) → 2MgO(s)
3. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)