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34 Cards in this Set

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IMPORTANT WORDS OF COMP
ATOMS
protons-postive
nuetroms-neutral
Electrons-negative
element
compound
bond
chemical formula
chemical reaction
first dESCRIP
MATTER IS MADE OF ATOMS, AND ATOMS ARE MADE OF THE SUBATOMIC PARTICLES PROTONS, NEUTORNS AND ELECTRONS
discribtor 2
atoms can get together to form compounds and mixtures
descriptor 3
elements are organized in the peroidc table according to their chemical propreties into families
descriptor 4
Atoms can get together and bond, forming molecules, by the interaction of their electrons
desc 5
the interaction among atoms occurs during chemical reactions, which can be summaries chemical equaions
THE TEACHER UNDERSTANDS THOSE THT RELATE TO THE CHEMICAL NATURE OF MATTER
ATOM
MATTER IS MADE UP OF ATOMS
ATOM IS THE SMALLES POSSIBLE PARTICLE OF A CHEMICAL ELEMENT THAT MAINTAINS ITS CHEMICAL PROPERITES
Maney scientists havef the atom contributed to the study of stucture of the atom and modifications are still being made?
d
One of the most popular models of the atom was created be Neil Bohr /
and new models have come along, the Bohr model is still useful today In atomic physics, the Bohr model depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus — similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity. This was an improvement on the earlier cubic model (1902), the plum-pudding model (1904), the Saturnian model (1904), and the Rutherford model (1911). Since the Bohr model is a quantum-physics based modification of the Rutherford model, many sources combine the two, referring to the Rutherford-Bohr model.

Introduced by Niels Bohr in 1913, the model's key success lay in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen; while the Rydberg formula had been known experimentally, it did not gain a theoretical underpinning until the Bohr model was introduced. Not only did the Bohr model explain the reason for the structure of the Rydberg formula, but it provided a justification for its empirical results in terms of fundamental physical constants.

The Bohr model is a primitive model of the hydrogen atom. As a theory, it can be derived as a first-order approximation of the hydrogen atom using the broader and much more accurate quantum mechanics, and thus may be considered to be an obsolete scientific theory. However, because of its simplicity, and its correct results for selected systems (see below for application), the Bohr model is still commonly taught to introduce students to quantum mechanics, before moving on to the more accurate but more complex valence shell atom. A related model was originally proposed by Arthur Erich Haas in 1910, but was rejected.
First of the three subatomic models and lots of empty space
Protons-
have a postive charge and are almost 2000 times as masive as electrons. Protons are spin-1/2 fermions and are composed of three quarks[1], making them baryons. The two up quarks and one down quark of the proton are also held together by the strong nuclear force, mediated by gluons.

Protons and neutrons are both nucleons, which may be bound by the nuclear force into atomic nuclei. The most common isotope of the hydrogen atom is a single proton (it contains no neutrons). The nuclei of other atoms are composed of various numbers of protons and neutrons. The number of protons in the nucleus determines the chemical properties of the atom and which chemical
First of the three subatomic models and lots of empty space:NUETORNS
The nucleus of all atoms (except the lightest isotope of hydrogen, which has only a single proton) consists of protons and neutrons. The number of neutrons determines the isotope of an element. For example, the carbon-12 isotope has 6 protons and 6 neutrons, while the carbon-14 isotope has 6 protons and 8 neutrons. Isotopes are atoms of the same element that have the same atomic number but different masses due to a different number of neutrons.

A neutron consists of two down quarks and one up quark. Since it has three quarks, it is classified as a baryon.

THEY HAVE A NEUTRAL CHARGE AND ROUGHLY HAVE THE SAME MASS AS PROTONS, THESE PARTICLE ARE FOUND IN NUCLEUS
First of the three subatomic models and lots of empty space-Electorns
HAVE A NEGATIVE CHARGE AND FOUND ORBITING TEH NUCLEUS IN VARIOUS ORBITALS, OR PATHS: THESE ARE THE LEAST MASSIVE PARTICLES
Ions-
An ion is an atom or group of bonded atoms which have lost or gained one or more electrons, making them negatively or positively charged. An ion consisting of a single atom is called a monatomic ion. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion (pronounced [ˈænaɪən]; an-eye-on) due to its attraction to anodes. A positively-charged ion, which has fewer electrons than protons, is known as a cation (pronounced [ˈkætaɪən]; cat-eye-on) due to its attraction to cathodes. A polyatomic anion that contains oxygen is sometimes known as an oxyanion.

Ions are denoted in the same way as electrically neutral atoms and molecules except for the presence of a superscript indicating the sign of the net electric charge and the number of electrons lost or gained, if more than one. For example: H+, SO42−. An alternate
carIONS
A positively-charged ion, which has fewer electrons than protons, is known as a cation (pronounced [ˈkætaɪən]; cat-eye-on) due to its attraction to cathodes
anions
negativly charged atoms
ELEMENTS, COMPOUNDS, MIXTURES-
ATOMIC NUMBER
In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. It is traditionally represented by the symbol Z. The atomic number uniquely identifies a chemical element. In an atom of neutral charge, the number of electrons also equals the atomic number.

The atomic number is closely related to the mass number, which is the number of protons and neutrons in the nucleus of an atom. The mass number defines the isotope of the element and often comes after the name of the element, e.g. carbon-14 (used in carbon dating).
ELEMENTS, COMPOUNDS, MIXTURES-ELEMENT
A chemical element, or element, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.[1]

Common examples of elements are hydrogen, nitrogen, and carbon. In total, 117 elements have been observed as of 2007, of which 94 occur naturally on Earth. Elements with atomic numbers greater than 82 (i.e,. bismuth and those above), are inherently unstable and undergo radioactive decay. In addition, elements 43 and 61 (technetium and promethium) have no stable isotopes, and also decay. However, even the elements up to atomic number 94 with no stable nuclei are nevertheless found in nature, as a result of the natural decay processes of uranium and thorium.[2]

All chemical matter consists of these elements. New elements are discovered from time to time through artificial nuclear reactions.
ELEMENTS, COMPOUNDS, MIXTURES-COMPOUND-iSOPTOPE
Isotopes are any of the several different forms of an element each having different atomic mass (mass number). Isotopes of an element have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have different mass numbers, which give the total number of nucleons—the number of protons plus neutrons.

A nuclide is any particular atomic nucleus with a specific atomic number Z and mass number A; it is equivalently an atomic nucleus with a specific number of protons and neutrons. Collectively, all the isotopes of all the elements form the set of nuclides. The distinction between the terms isotope and nuclide has somewhat blurred, and they are often used interchangeably. Isotope is best used when referring to several different nuclides of the same element; nuclide is more generic and is used when referencing only one nucleus or several nuclei of different elements. For example, it is more correct to say that an element such as fluorine consists of one stable nuclide rather than that it has one stable isotope.

In IUPAC nomenclature, isotopes and nuclides are specified by the name of the particular element, implicitly giving the atomic number, followed by a hyphen and the mass number (e.g. helium-3, carbon-12, carbon-13, iodine-131 and uranium-238). In symbolic form, the number of nucleons is denoted as a superscripted prefix to the chemical symbol (e.g. 3He, 12C, 13C, 131I and 238U).

The term isotope was coined in 1913 by Margaret Todd, a Scottish doctor, during a conversation with Frederick Soddy (to whom she was distantly related by marriage).[1] Soddy, a chemist at Glasgow University, explained that it appeared from his investigations as if several elements occupied each position in the periodic table. Hence Todd suggested the Greek for "at the same place" as a suitable name. Soddy adopted the term and went on to win the Nobel Prize for Chemistry in 1921 for his work on radioactive substances.


In the bottom right corner of JJ Thomson's photographic plate are markings for the two isotopes of neon: neon-20 and neon-22.In 1913, as part of his exploration into the composition of canal rays, JJ Thomson channeled a stream of ionized neon through a magnetic and an electric field and measured its deflection by placing a photographic plate in its path. Thomson observed two patches of light on the photographic plate (see image on right), which suggested two different parabolas of deflection. Thomson concluded that some of the atoms in the gas were of higher mass than the rest
ELEMENTS, COMPOUNDS, MIXTURES-MIXTURE
In chemistry, a mixture is a substance made by combining two or more different materials in such a way that no chemical reaction occurs. A mixture can usually be separated back into its original components. Some examples of Mixtures are oil, ocean water and soil. Mixtures are the product of a mechanical blending or mixing of chemical substances like elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup [1] . While there are no chemical changes in a mixture, physical properties of a mixture, such as its melting point, may differ from those of its components. Mixtures can usually be separated by mechanical means.

There are two different types of mixtures: homogeneous mixtures (including solutions and colloidal dispersions) and heterogeneous mixtures (Suspensions).
Elements of the Periodic table
ATOMIC NUMBER
ATOMIC MASS
FAMILIES
HALOGENS
INERT GASES
METALS
ALKALI METALS
ALKALINE EARTH METALS
TRANSITION METALS
LANTHANIDE AND ACTINIDE SERIES OF METALS
atomic number
In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. It is traditionally represented by the symbol Z. The atomic number uniquely identifies a chemical element. In an atom of neutral charge, the number of electrons also equals the atomic number.

The atomic number is closely related to the mass number, which is the number of protons and neutrons in the nucleus of an atom. The mass number defines the isotope of the element and often comes after the name of the element, e.g. carbon-14 (used in carbon dating).
atomic mass
The atomic mass (ma) is the mass of an atom at rest, most often expressed in unified atomic mass units.[1] The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom (when the atom is motionless). The atomic mass is sometimes incorrectly used as a synonym of relative atomic mass, average atomic mass and atomic weight; however, these differ subtly from the atomic mass. The atomic mass is defined as the mass of an atom, which can only be one isotope at a time and is not an abundance-weighted average. The actual numerical difference is usually very small such that it does not affect most bulk calculations but such an error can be critical when considering individual atoms.

The relative atomic mass (Ar) (also known as atomic weight and average atomic mass) is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance.[2] This is frequently used as a synonym for the standard atomic weight and is not incorrect to do so since the standard atomic weights are relative atomic masses, although it is less specific to do so. Relative atomic mass also refers to non-terrestrial environments and highly specific terrestrial environments that deviate from the average or have different certainties (number of significant figures) than the standard atomic weights.

The standard atomic weight refers to the mean relative atomic mass of an element in the local environment of the Earth's crust and atmosphere as determined by the IUPAC Commission on Atomic Weights and Isotopic Abundances.[3] These are what are included in a standard periodic table and is what is used in most bulk calculations. An uncertainty in brackets is included which often reflects natural variability in isotopic distribution rather than uncertainty in measurement.[4] For synthetic elements the isotope formed depends on the means of synthesis, so the concept of natural isotope abundance has no meaning. Therefore, for synthetic elements the total nucleon count of the most stable isotope (ie, the isotope with the longest half-life) is listed in brackets in place of the standard atomic weight. Lithium represents a unique case where the natural abundances of the isotopes have been perturbed by human activities to the point of affecting the uncertainty in its standard atomic weight, even in samples obtained from natural sources such as rivers.

The relative isotopic mass is the relative mass of the isotope, scaled with carbon-12 as exactly 12. No other isotopes have whole number masses due to the different mass of neutrons and protons, as well as loss/gain of mass to binding energy. However, since mass defect due to binding energy is minimal compared to the mass of a nucleon, rounding the atomic mass of an isotope tells you the total nucleon count. Neutron count can then be derived by subtracting the atomic number.
What is "families" defined in the chemical aspects of mattter
they are elements are grouped into families according to their chemical compounds
HALOGENS
The halogens or halogen elements are a series of nonmetal elements from Group 17 (old-style: VII or VIIA; Group 7 IUPAC Style) of the periodic table, comprising fluorine, F; chlorine, Cl; bromine, Br; iodine, I; and astatine, At. The undiscovered element 117, temporarily named ununseptium, may also be considered a halogen.

The group of halogens is the only group which contains elements in all three familiar states of matter at standard temperature and pressure.
INERT GASES
Inert gases and noble gases are not exactly synonyms although some of the objects they describe overlap. "Noble gas" refers to inert elemental gases only whereas "inert gas" refers to molecular as well as elemental gases which are inert. Also "inert gas" is an archaic term for noble gas.
An inert gas is any gas that is not reactive under normal circumstances. Unlike the noble gases an inert gas is not necessarily elemental and are often molecular gases. Like the noble gases the tendency for non-reactivity is due to the valence, the outermost electron shell, being complete in all the inert gases. This is a tendency, not a rule, as noble gases and other "inert" gases can react to form compounds.

Although the term "rare gases" is sometimes used as a synonym for the elemental inert gases, i.e. noble gases—they are only rare relative to other gases found in Earth's atmosphere (i.e. air) with the exception of argon which makes up a significant portion of air, around %0.934; hardly rare at all. Because of their unreactivity, and perhaps their relative scarcity, the inert gases were not discovered until helium was discovered to exist in the Sun, where it is abundant, before it was discovered to exist in Earth's atmosphere. This is possible through the analysis of spectral lines.

Helium and neon are the only true elemental inert gases, because they do not form any (known) true chemical compounds, unlike the heavier noble gases (argon, krypton, xenon and radon).

In marine applications, inert gas refers to gases with a low content of oxygen that are used to fill void spaces in and around tanks for explosion protection. There are two types of inert gas which are either based on nitrogen or on flue gas.
METALS
In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. Metals form ionic bonds with non-metals. They are sometimes described as a lattice of positive ions surrounded by a cloud of delocalized electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals. Most elements on this line are metalloids, sometimes called semi-metals; elements to the lower left are metals; elements to the upper right are nonmetals.

An alternative definition of metals is that they have overlapping conduction bands and valence bands in their electronic structure. This definition opens up the category for metallic polymers and other organic metals, which have been made by researchers and employed in high-tech devices. These synthetic materials often have the characteristic silvery-grey reflectiveness (luster) of elemental metals.

The traditional definition focuses on the bulk properties of metals. They tend to be lustrous, ductile, malleable, and good conductors of electricity, while nonmetals are generally brittle (if solid), lack luster, and are insulators.
ALKAI METALS
Known as Alkaline metals and are very reactive


The alkali metals are a series of elements comprising Group 1 (IUPAC style) of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). (Note that hydrogen, although nominally also a member of Group 1, very rarely exhibits behavior comparable to the alkali metals). The alkali metals provide one of the best examples of group trends in properties in the periodic table, with well characterized homologous behavior down the group.

The alkali metals are all highly reactive and are rarely found in elemental form in nature. As a result, in the laboratory they are stored under mineral oil. They also tarnish easily and have low melting points and densities. Potassium and Rubidium are very weakly radioactive (harmless) due to the presence of long duration radioactive isotopes.

The alkali metals are silver-colored (caesium has a golden tinge), soft, low-density metals, which react readily with halogens to form ionic salts, and with water to form strongly alkaline (basic) hydroxides. These elements all have one electron in their outermost shell, so the energetically preferred state of achieving a filled electron shell is to lose one electron to form a singly charged positive ion.

Hydrogen, with a solitary electron, is usually placed at the top of Group 1 of the periodic table, but it is not considered an alkali metal; rather it exists naturally as a diatomic gas. Removal of its single electron requires considerably more energy than removal of the outer electron for the alkali metals. As in the halogens, only one additional electron is required to fill in the outermost shell of the hydrogen atom, so hydrogen can in some circumstances behave like a halogen, forming the negative hydride ion. Binary compounds of hydride with the alkali metals and some transition metals have been prepared. Under extremely high pressure, such as is found at the core of Jupiter, hydrogen does become metallic and behaves like an alkali metal; see metallic hydrogen.

Alkali metals have the lowest ionization potentials in their respective periods, as removing the single electron from the outermost shell gives them the stable inert gas configuration. But their second ionization potentials are very high, as removing an electron from a species having a noble gas configuration is very difficult.

Contents [hide]
1 Reactions
1.1 Reactions in water
1.2 Reaction in ammonia
2 Trends
3 Biological occurrences
4 Reference Material
5 See also
6 External links
ALKALINE EARTH METALS
the second most reative reative on the table and when mixed in solutoion cause PH IS GREATER than 7


The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). The alkaline earth metals provide a good example of group trends in properties in the periodic table, with well characterised homologous behaviour down the group.

The alkaline earth metals are silvery colored, soft, low-density metals, which react readily with halogens to form ionic salts, and with water, though not as rapidly as the alkali metals, to form strongly alkaline (basic) hydroxides. For example, where sodium and potassium react with water at room temperature, magnesium reacts only with steam and calcium with hot water:

Mg + 2H2O → Mg(OH)2 + H2
TRANSITION METALS
these elements can arrange their electorns differently than the other elements, In chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings:

It commonly refers to any element in the d-block of the periodic table, including zinc, cadmium and mercury. This corresponds to groups 3 to 12 on the periodic table.
More strictly, IUPAC defines a transition metal as "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." By this definition, zinc, cadmium, and mercury are excluded from the transition metals, as they have a d10 configuration. Only a few transient species of these elements that leave ions with a partly filled d subshell have been formed, and mercury(I) only occurs as Hg22+, which does not strictly form a lone ion with a partly filled subshell, and hence these three elements are inconsistent with the latter definition.[1] They do form ions with a 2+ oxidation state, but these retain the 4d10 configuration. Element 112 may also be excluded although its oxidation properties are unlikely to be observed due to its radioactive nature. This definition corresponds to groups 3 to 11 on the periodic table.
The first definition is simple and has traditionally been used. However, many interesting properties of the transition elements as a group are the result of their partly filled d subshells. Periodic trends in the d block (transition metals) are less prevailing than in the rest of the periodic table. Going across a period, the valence doesn't change, so the electron being added to an atom goes to the inner shell, not outer shell, strengthening the shield. [2]

The (loosely defined) transition metals are the 40 chemical elements 21 to 30, 39 to 48, 71 to 80, and 103 to 112. The name transition comes from their position in the periodic table of elements. In each of the four periods in which they occur, these elements represent the successive addition of electrons to the d atomic orbitals of the atoms. In this way, the transition metals represent the transition between group 2 elements and group 13 elements.
LANTHAIDE AND ANTINIDE SERIES OF METALS
ACTINIDE SERIES OF METALS
There are two rows under the table. The Lanthanide and Actinide series. The Lanthanide series can be found naturally on Earth. Only one element in the series is radioactive. The Actinide series is much different. They are all radioactive and some are not found in nature. Some of the elements with higher atomic numbers have only been made in labs. There are special laboratories across the world that specialize in experimenting on elements. Some of these particle accelerators have pounded atomic particles into elements with lower atomic numbers. The buildup of additional parts creates short-lived elements.


MEET THE FAMILY
Fifteen elements that start with actinium (Ac) at atomic number 89 and finishing up with lawrencium (Lr) at number 103. It's doubtful your teachers will ever ask you to remember all of the elements in the series, just remember actinium.
ChemicAL Bonds and Chemical reactios
chemical reaction is a process that results in the interconversion of chemical substances.[1] The substance or substances initially involved in a chemical reaction are called reactants. Chemical reactions are characterized by a chemical change, and they yield one or more products which are, in general, different from the reactants. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. On the classical definition, therefore, there are only two types of chemical reaction: redox reactions and acid-base reactions. The former involve the motion of lone electrons and the latter of an electron pair.

Different chemical reactions are used in combinations in chemical synthesis in order to get a desired product. In biochemistry, series of chemical reactions aided by enzymes form metabolic pathways, since straight synthesis of a product would be energetically
chemical formula
chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs. For molecular compounds, it identifies each constituent element by its chemical symbol and indicates the number of atoms of each element found in each discrete molecule of that compound. If a molecule contains more than one atom of a particular element, this quantity is indicated using a subscript after the chemical symbol (although 19th-century books often used superscripts). For ionic compounds and other non-molecular substances, the subscripts indicate the ratio of elements in the empirical formula.
Molecular and structural formula
For example methane, a simple molecule consisting of one carbon atom bonded to four hydrogen atoms has the chemical formula:

CH4
and glucose with six carbon atoms, twelve hydrogen atoms and six oxygen atoms has the chemical formula:

C6H12O6.
A chemical formula supplies information about the types and spatial arrangement of bonds in the chemical, though it does not necessarily specify the exact isomer. For example ethane consists of two carbon atoms single-bonded to each other, with each carbon atom having three hydrogen atoms bonded to it. Its chemical formula can be rendered as CH3CH3. If there were a double bond between the carbon atoms (and thus each carbon only had two hydrogens), the chemical formula may be written: CH2CH2, and the fact that there is a double bond between the carbons is assumed. However, a more explicit and correct method is to write H2C:CH2 or H2C=CH2. The two dots or lines indicate that a double bond connects the atoms on either side of them.

A triple bond may be expressed with three dots or lines, and if there may be ambiguity, a single dot or line may be used to indicate a single bond.

Molecules with multiple functional groups that are the same may be expressed in the following way: (CH3)3CH. However, this implies a different structure from other molecules that can be formed using the same atoms (isomers). The formula (CH3)3CH implies a chain of three carbon atoms, with the middle carbon atom bonded to another carbon:



and the remaining bonds on the carbons all leading to hydrogen atoms. However, the same number of atoms (10 hydrogens and 4 carbons, or C4H10) may be used to make a straight chain: CH3CH2CH2CH3.

The alkene but-2-ene has two isomers which the chemical formula CH3CH=CHCH3 does not identify. The relative position of the two methyl groups must be indicated by additional notation denoting whether the methyl groups are on the same side of the double bond (cis or Z) or on the opposite sides from each other.(trans or E)


[edit] Polymers
chemical reaction
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!



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