Chemistry of Matter

1
Chemistry of Matter

• 8th Grade Science
• School Year 2003-2004
• Luther Burbank School
• Mr. Frank Canzolino Room 204

2
8th Grade Science

• Week 7.1
• Day 30
• Monday
• October 6, 2003

3
Question of the Day

• Name three common items that you think are
  chemical reactions.

4
Question of the Day

• Name three common items that you think are
  chemical reactions.
• Zillions of possible answers
• Iron rusting
• Burning match
• Baking bread
• Magnesium strip burning

5
Where Weve Been

• Chemical Bonding
• All matter is made of small particles called
  atoms
• Chemical bonding is the combination of elements
  to create new substances
• The atom consists of a nucleus containing protons
  and neutrons and energy levels containing
  electrons
• Bonding involves the electrons in the outermost
  energy level (valence electrons)

• Ionic bonds
• Ionic bonding involves the transfer of electrons
  and the formation of ions
• Ionization energy is the amount of energy needed
  to remove an electron from a neutral atom
• Electron affinity is the tendency of an atom to
  attract electrons.
• The placement of ions in an ionic compound
  results in a crystal lattice.

6
Where Weve Been

• Covalent Bonds
• Covalent bonding involves a sharing of electrons
• A molecule is the smallest unit of a covalently
  bonded substance

• Covalent Bonds
• Network solids are substances whose molecules are
  very large because the atoms in the substance
  continue to bond to one another
• A polyatomic ion is a group of covalently bonded
  atoms that act like a single atom when it
  combines with other atoms.

7
Where Weve Been

• Metallic Bonds
• The basis of metallic bonding is the sea of
  mobile electrons that surrounds the nuclei and is
  simultaneously attracted by them.
• The mobile electrons explain thermal and
  electrical conductivity and mechanical properties

• Predicting Types of Bonds
• The oxidation number, or combining capacity, of
  an atom refers to the number of electrons the
  atom gains, loses or shares when it forms
  chemical bonds.
• The oxidation number of an atom can be determined
  by knowing the numbers of valence electrons.

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Where Were Going Nature of Chemical Reactions

• Introduction to the characteristics of chemical
  reactions
• Chemical reactions always produce a change in
  properties and energy of the substances involved
• Reactants and Products

• Breaking and reforming chemical bonds to form new
  substances with different chemical and physical
  properties and amounts of energy
• Depends on number of valence electrons
• Collision of particles of the reactants determine
  the rate of chemical reaction

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Where Were GoingChemical Equations

• Chemical equations are used to represent chemical
  reactions
• Elements are represented by symbols and compounds
  are represented by formula
• Chemical equations represent the conservation of
  mass

• Chemical equations can be used to represent the
  changes that occur during chemical reactions
• Mass is always conserved during a chemical
  reaction

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Where Were GoingTypes of Chemical Reactions

• Four types of chemical reactions
• Synthesis
• Decomposition
• Single replacement
• Double replacement
• Opposite of synthesis reaction is decomposition
  reaction

• Bonds are broken and reformed
• Shared characteristics
• Reactants change to products

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Where Were GoingEnergy of Chemical Reactions

• Chemical reactions can be classified according to
  energy changes
• Exothermic reactions
• Energy is released
• Endothermic reactions
• Energy is absorbed
• Energy of reactants change during a chemical
  reaction

• Reactants must reach the activation energy before
  the products can form
• The effect of energy can be shown on a diagram

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Where Were GoingRates of Chemical Reaction

• Factors influencing chemical reactions
• Concentration of reactants
• Surface area of solid reactants
• Temperature
• Catalyst

• Increasing the temperature, concentration or
  surface area of reactants usually increases the
  reaction rate
• Catalysts decrease activation energy

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Chemical ReactionsIntroduction

• Chemical Reaction
• A process that changes original substances
  physical (how things look and behave) and
  chemical properties into new substances having
  different physical and chemical properties.
• The substance(s) that enter into the reaction are
  called the reactant(s)
• The substance(s) formed as a result of the
  reaction are called the product(s)

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Chemical Reactions The Hindenburg
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Chemical ReactionsThe Hindenburg
16
Chemical Reactions The Hindenburg

• The Hindenburg was filled with Hydrogen
• During its landing in New Jersey, an explosion
  occurred.
• What to chemicals were the reactants in the
  chemical reaction?

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Chemical Reactions The Hindenburg

• The Hindenburg was filled with Hydrogen
• During its landing in New Jersey, an explosion
  occurred.
• What to chemicals were the reactants in the
  chemical reaction?
• Hydrogen and Oxygen

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Chemical Reactions The Hindenburg

• The Hindenburg was filled with Hydrogen
• During its landing in New Jersey, an explosion
  occurred.
• What to chemicals were the reactants in the
  chemical reaction?
• Hydrogen and Oxygen
• What was the product?

19
Chemical Reactions The Hindenburg

• The Hindenburg was filled with Hydrogen
• During its landing in New Jersey, an explosion
  occurred.
• What to chemicals were the reactants in the
  chemical reaction?
• Hydrogen and Oxygen
• What was the product?
• H20 (water)

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Chemical ReactionsIntroductionProducts and
Reactants

• Remember the magnesium demonstration?
• We changed a strip of Mg metal into a white
  powder MgO
• This was a chemical reaction between the
  reactants Mg and the O in the air, forming a
  product MgO

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Chemical ReactionTheir Nature

• Chemical Reactions
• Always result in a new substance
• The new product has different properties, both
  chemical and physical than the original reactants

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Chemical ReactionsWhy they happen

• Chemical reactions involve the valence electrons
• Chemical bonds occur so that atoms can achieve a
  filled outer energy level either by gaining or
  losing (ionic), or sharing electrons

Ionic Bonding
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Chemical ReactionsWhy they happen

• Chemical reactions involve the valence electrons
• Chemical bonds occur so that atoms can achieve a
  filled outer energy level either by gaining or
  losing (ionic), or sharing (covalent) electrons

Covalent Bonding
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Chemical ReactionsWhy they happen

• Chemical reactions involve the valence electrons
• Chemical bonds occur so that atoms can achieve a
  filled outer energy level either by gaining or
  losing (ionic), or sharing (covalent, metallic)
  electrons

Metallic Bonding
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Chemical ReactionsReaction Capacity

• The arrangement of the valence electrons
  determine the ease with which an atom will form a
  chemical bond
• Remember, an atom whose valence electron energy
  level is filled will not bond (inert or noble
  gases)
• The ease with which an atom will form a chemical
  bond is known as its bonding capacity and is what
  controls the ability of the atom to undergo
  chemical reactions.

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Chemical ReactionsReaction Capacity

• During a chemical reaction, atoms can form
  molecules and molecules can break apart to form
  atoms
• Any way you look at it, new substances are formed
  as bonds are broken, formed, re-formed, and
  rearranged

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Homework

• Page 41, 2-1 Section Review, 1-3
• Page 60, True or False, 1
• Page 61, Concept Mastery, 1
• Measuring Project Dry Run Wednesday

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8th Grade Science

• Week 7.2
• Day 31
• Tuesday
• October 7, 2003

29
Question of the Day

• Which is a chemical reaction cutting a piece of
  paper into teeny-tiny pieces or a rusting piece
  of steel? Why did you say what you said?

30
Homework

• Page 41, 2-1 Section Review, 1-3
• A chemical reaction is a process in which the
  physical and chemical properties of the original
  substances change as new substances with
  different physical and chemical properties are
  formed
• A reactant is a substance that enters into a
  chemical reaction. A product is the substance
  that is produced by a chemical reaction
• The arrangement of electrons in an atom
  determines the bonding capacity of an atom. The
  bonding capacity of an atom determines its
  chemical properties, or its ability to undergo
  chemical reactions

31
Homework

• Page 60, True or False, 1
• The substances formed as a result of a chemical
  reaction are called reactants.
• This is false, the substances formed are call the
  products.

32
Homework

• Page 61, Concept Mastery, 1
• A chemical reaction is a process in which the
  physical and chemical properties of the original
  substances change as new substances with
  different physical and chemical properties are
  formed.
• Substances react chemically because the atoms of
  substances have complementary bonding capacities.
  The atoms of a substance form chemical bonds with
  other atoms in order to complete the outermost
  energy levels.

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Chemical ReactionsChemical Equations

• A chemical equation is used to describe a
  chemical reaction

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Chemical ReactionsChemical Equations
O

• Chemists have developed a convenient method to
  express chemical reactions, the chemical equation
• The first step to writing a chemical equation is
  to write the chemical symbols or formula for the
  reactants and the products

Mg
2Mg and O2
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Chemical ReactionsChemical Equations
O

• You need to show that certain substances combine
• Use the plus sign () to show those reactants
  that combine

Mg
2Mg O2
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Chemical ReactionsChemical Equations
O

• Draw an arrow to show that the reactants are
  combining to form new products.

Mg
2Mg O2 gt
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Chemical ReactionsChemical Equations
O

• Then show the products of the reaction

Mg
2Mg O2 gt 2MgO Energy
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Chemical ReactionsConservation of Mass

• During a chemical reactions, atoms are neither
  created or destroyed
• Only the bonds between atoms and/or molecules are
  broken and the atoms and/or molecules are
  rearranged
• The number of atoms before and after a chemical
  reaction is the same
• Energy is released or gained because of the
  rearrangement of the bonds

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Chemical ReactionsConservation of Mass

• Notice that the number of atoms on both sides of
  the arrow are the same
• 2 Mg atoms
• 2 O atoms
• Notice also that we needed two Mg atoms for every
  O2 molecule because oxygen exists in nature as
  the molecule, not the atom
• The change that occurred is only a result of the
  rearrangement of the atoms and bonds

2Mg O2 gt 2MgO Energy
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Chemical ReactionsConservation of Mass

• Each atom has an atomic number (the number of
  protons in the nucleus) and an atomic weight
  (mass of protons, neutrons and electrons)
• Since the number of atoms of each element is the
  same before and after a chemical reaction, the
  total mass of the reactants must equal the total
  mass of the products

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Chemical ReactionsConservation of Mass

• Mass is neither created or destroyed during a
  chemical reaction
• This is called the Conservation of Mass

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Chemical ReactionsBalancing Chemical Equations

• A chemical equation must show that atoms are
  neither created or destroyed.
• This means that the number of each type of atom
  on each side of the equation must be the same
• When the atoms are the same on each side of the
  equation, the equation is said to be balanced

43
Homework

• Page 61, Critical Thinking and Problem Solving, 1

44
Measuring Project

• You have the remainder of the period to prepare
  for the oral presentation. A dry run will be done
  tomorrow, final presentation is Friday.

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8th Grade Science

• Week 7.3
• Day 32
• Wednesday
• October 8, 2003

46
Question of the Day

• Consider the chemical equation
• Mg O2 gt MgO Energy
• Is this a balanced equation? If so, why? If not,
  show the balanced equation.
• Do the same for the reaction between sodium metal
  (Na) and oxygen gas (O2) that forms sodium oxide
  (Na2O)

47
Question of the Day

• Consider the chemical equation
• Mg O2 gt MgO Energy
• Is this a balanced equation? If so, why? If not,
  show the balanced equation.
• This is not a balanced equation. Since oxygen
  exists in nature as the O2 molecule, two oxygen
  atoms must be on the products side of the
  equation. Since that would require two Mg atoms
  to combine with the two oxygen atoms, the correct
  equation must start with two Mg atoms on the
  reactants side of the equation. The correct
  equation must be 2Mg O2 gt 2MgO Energy

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Question of the Day

• Do the same for the reaction between sodium metal
  (Na) and oxygen gas (O2) that forms sodium oxide
  (Na2O)
• 4Na O2 gt 2Na2O

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FYI

• http//homepage.mac.com/solarpowered/FileSharing39
  .html

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Homework

• Critical Thinking and Problem Solving 1
• 2PbO2 gt 2PbO O2
• Ca 2H2O gt Ca(OH)2 H2
• Zn S ZnS
• BaCl2 Na2SO4 gt BaSO4 2NaCl
• 2Al Fe2O3 gt Al2O3 2Fe
• C12H22O11 gt 12C 11H2O

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8th Grade Science

• Week 7.4
• Day 33
• Thursday
• October 9, 2003

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Question of the Day

• A reaction in which a substance burns in oxygen
  is a synthesis reaction (two or more simple
  substances react to form a new, more complex
  substance). Why do you think that smoking is not
  permitted where oxygen is being administered?

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Question of the Day

• A reaction in which a substance burns in oxygen
  is a synthesis reaction (two or more simple
  substances react to form a new, more complex
  substance). Why do you think that smoking is not
  permitted where oxygen is being administered?
• Because of the risk of fire and explosion

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Types of Chemical Reactions

• There are four general types of chemical reaction
• Synthesis
• A B gt C
• Decomposition
• C gt A B
• Single Replacement
• A BX gt AX B
• Double Replacement
• AX BY gt AY BX

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Synthesis

• Two or more simple substances combine to form a
  new substance
• A B gt C
• 2Na Cl2 gt 2NaCl
• Examples
• Corrosion of metal
• Burning

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Decomposition

• A complex substance breaks down to form two or
  more simple substances
• C gt A B
• H2CO3 gt H2O CO2
• Fizz in soda is a decomposition reaction

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Single Replacement

• An uncombined element replaces an element that is
  part of a compound
• A BX gt AX B
• 2Na 2H2O gt 2NaOH H2
• Explosion hazard, do not try at home
• Most single replacement reactions do not cause
  explosions

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Double Replacement

• Different elements in two different compounds
  replace each other
• AX BY gt AY BX
• MgCO3 2HCl gt MgCl2 H2CO3
• This is what happens when you use Rolaids
• Can you figure out why you burp?

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Double Replacement

• Different elements in two different compounds
  replace each other
• AX BY gt AY BX
• MgCO3 2HCl gt MgCl2 H2CO3
• This is what happens when you use Rolaids
• Can you figure out why you burp?
• You burp because the H2CO2 undergoes a
  decomposition reaction
• H2CO3 gt H2O CO2

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Balancing Equations Group Practice/Homework

• Worksheet 1-10
• Balance Equation
• Specify type of reaction
• Typo 6, should be
• C10H16

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8th Grade Science

• Week 7.5
• Day 34
• Friday
• October 10, 2003

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Question of the Day

• Identify the type of chemical reaction defined by
  the general chemical equation shown.
• AX BY gt AY BX
• A B gt C
• A BX gt AX B
• C gt A B

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Question of the Day

• Identify the type of chemical reaction defined by
  the general chemical equation shown.
• AX BY gt AY BX
• Double Replacement
• A B gt C
• Synthesis
• A BX gt AX B
• Single Replacement
• C gt A B
• Decomposition

64
Homework

• H2 O2 gt H2O
• 2H2 O2 gt 2H2O (Synthesis)
• S8 O2 gt SO3
• S8 12O2 gt 8SO3 (Synthesis)
• HgO gt Hg O2
• 2HgO gt 2Hg O2 (Decomposition)
• Zn HCl gt ZnCl2 H2
• Zn 2HCl gt ZnCl2 H2 (Single Replacement)

65
Homework

• Na H2O gt NaOH H2
• 2Na 2H2O gt 2NaOH H2 (Single Replacement)
• C10H16 Cl2 gt C HCl
• C10H16 8Cl2 gt 10C 16HCl (Single Replacement)
• Si2H3 O2 gt SiO2 H2O
• 4Si2H3 11O2 gt 8SiO2 6H2O (Double
  Replacement)
• Fe O2 gt Fe2O3
• 4Fe 3O2 gt 2Fe2O3 (Synthesis)

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Homework

• C7H6O2 O2 gt CO2 H2O
• 2C7H6O2 11O2 gt 14CO2 6H2O (Double
  Replacement)
• FeS2 O2 gt Fe2O3 SO2
• 4FeS2 11O2 gt 2Fe2O3 8SO2 (Double Replacement)

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Measuring Project

• Final Presentations

68
Chemical Reactions

• Laboratory

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Chemical ReactionsVocabulary

• Chemical Bonding
• Ionic Bonding
• Covalent Bonding
• Metallic Bonding
• Chemical Reaction
• Reactant
• Product
• Bonding Capacity
• Chemical Equation

• Conservation of Mass
• Balanced Chemical Equations
• Synthesis Reaction
• Decomposition Reaction
• Single Replacement Reaction
• Double Replacement Reaction

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8th Grade Science

• Week 8.1
• Day 35
• Monday
• October 13, 2003

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Holiday

• Columbus Day