Electron glue

1
Electron glue

• bonding

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ChemCatalyst

• A gold ring is made up of individual gold atoms.
• What keeps the pieces of each atom together?
• Why dont the atoms of gold fall apart from each
  other?
• What subatomic particle do you think are
  responsible for keeping the atoms together in a
  solid?

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Chem Catalyst (solubility)

• If you were to drop a spoonful of salt (NaCl)
  into a glass of water, would the salt dissolve?
• Would a gold ring dropped into a glass of water
  dissolve?
• F. Why do these substance react so differently to
  water?

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Chem catalyst (Conductivity)

• G. What flows in an electric current?
• H. What makes a material a good conductor?
• I. Is table salt a conductor or an insulator?

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The Big Question

• Are properties of solubility and conductivity
  related?
• What determines a compounds level of solubility
  and conductivity ?
• How can we use bonding to explain the properties
  of substances we encounter?

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You will be able to

• Classify the bonding that in a number of
  compounds
• Indicate which compounds will dissolve or conduct
  electricity in an aqueous solution

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Notes

• A chemical bond is an attraction between atoms
  that holds them together in space.
• A chemical bond is a force
• A chemical bond is related to the charges of
  subatomic particles

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• Solubility measures how easy a material dissolves
  into a solvent
• Conductivity measures how easy it is for energy
  to flow through a material

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Activity

• Purpose This lesson helps to explain the
  physical properties conductivity and solubility
  of basic substances by examining the types of
  bonds that exist between the atoms of these
  substances.

(cont.)
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Step oneBuild conductivity meters

• We use Christmas Tree lights with wires to form a
  conductivity meter

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(cont.)
Regular wires may be included instead of
alligator clipped wires
(cont.)
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Intro to electricity

• What is a circuit?
• Open Circuit
• Closed circuit
• Short Circuit

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Demonstration of dissolving and conductivity

• Test to see if Kool-Aid will dissolve and/or
  conduct electricity
• Both solid and solution (if applicable)

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Lab set up

1. Form groups
2. Make sure each member has their own copy of all
   handouts
3. There are a number of stations around the room,
   groups will be rotating through them
4. Groups will take only their comp books with them
   as they move through the stations

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Procedures to take at the stations

• Do not leave the conductivity meter connected in
  circuit too long. These Christmas light burn out
  very fast
• Do not connect wire to both ends of battery,
  creating a short (dangerous). This burns out the
  batteries extremely fast. Points will be
  deducted from group score for lab if this occurs
• Once you test the materials at a station take
  paper clips off of beaker and dry them off.
  Separate all material
• Do not place paper clips used to test one
  material or solution into a different one,
  (minimize Contamination)

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Extra Lab Precautions

• Be aware about special conditions for the
  following materials
• Ethanol (strong smelling)
• Calcium Chloride Solution (can damage paper
  clip, stain clothes)

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When Done

• Answer questions based on lab with your
  partner(s)
• Make sure your have cleaned up after yourself
• Question and answer session will follow

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Solute Formula and Name Pure Substance Aqueous Solution Level of Solubility What type of mixture? Signs of chemical reaction?
Conduct? Strong or weak Conduct? Str or wk? Heterogeneous or Homogeneous With Paper clips
KCl (s) Potassium Chloride
Al(s) Aluminum
C12H22O11(s) Sugar
NaCl(s) Salt
SiO2(s) Sand
C20H42(s) Parrafin wax
C2H6O(l) Ethanol
CaCl2(s), calcium chloride
Tap Water (mixture)
H2O(l) Distilled
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Classify the materials into 4 groups based on
their ability to conduct and dissolve
Conducts, dissolves Conducts, does not dissolve
Dissolves, does not conduct Does not dissolve or conduct
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Most objects can be sorted into one of 4
categories

• Whether it dissolves or not
• Whether it conducts or not

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Dissolves
Notes
Yes
No
Conducts
Conducts
Yes
Yes
No
No
NaCl salt CaCl2 calcium chloride KCl potassium chloride H2O tap water C12H22O11 sugar C2H6O isopropyl Cu copper Al aluminum SiO2 sand C20H42 paraffin wax
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Answer using Information from lab

• For a material to both conduct and dissolve, what
  must be true about its elements?
• For the material to not dissolve but conduct,
  what must be true about its elements?
• What is the common chemical feature about those
  materials that do not fall into the previous
  groups?

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Solubility, Conductivity and chemical bonds

• Solubility depends on the strength of bonds
  between molecules
• Strong bonds ? less soluble
• Conductivity depends on the strength on the bonds
  between valence electrons and nucleus
• Strong bonds ? less conductive

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Wrap-Up

• Not all substances conduct electricity and/or
  dissolve in water.
• Substances that do conduct electricity involve
  either solid metals, or metal-nonmetal compounds
  dissolved in water.

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(cont.)
Covalent Network
Molecular Covalent
Ionic
Metallic
(cont.)
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Activity number 1

• Identify handout with pictures of atoms
• Read about the 4 models of atomic bonds
• Fill in chart of the materials properties for
  each type of bond in your comp book
• Identify and label each item in the diagrams

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Chart of Bond Properties
Property name Description Ionic Bond Covalent Bond Metallic Bond Molecular Covalent bond
Atom Composition Metal or non-metal
Solubility in water Dissolves or not
Conduction of Electricity Yes, no, sometimes
Toughness Brittle, bendable
Durability Hard, soft
State of matter Are bonds most likely in S, L, and/or G
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Class Activity number 2

• Step two
• Classify 15 substances below according to which
  of the four models best describes their makeup
  and properties
• Make a chart in comp book or on paper

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List of substances
Substance number Chemical Formula Common Name Substance number Chemical Formula Common Name
1 Na (s) Sodium 9 Cu (s) Copper
2 NaCl (s) Salt 10 H20 (l) Distilled Water
3 Hg (l) Mercury 11 CH4 (g) Gas
4 C (s) Diamond 12 Si (s) Silicon (computer chips)
5 CuCl2 (aq) Copper chloride solution 13 Pt (s) Platinum (jewelry)
6 SiO2 (s) Sand 14 CH3CH2OH(l) Ethanol (drinking alcohol)
7 NaOH Liquid Drano 15 NaCl (aq) Saltwater
8 MgSO4 Epsom Salt
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Names of substances are written into the chart
below the bond type
Ionic Covalent Network Metallic Molecular Covalent





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Model 1 Model 2 Model 3 Model 4
Ionic Covalent Metallic Molecular Covalent
NaCl (s) Nacl (aq) C (s) Na (s) CH4 (g)
CuCl2 (aq) Si (s) Hg (l) CH3CH2OH (l)
NaOH (aq) SiO2 (s) Cu (s) H2O (l)
MgSO4 (s)
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Notes

• Model 1 IONIC
• Properties
• Made of metal and non-metal atoms
• Dissolves in water
• Conducts electricity when dissolved but not when
  solid
• Brittle solids
• Description of drawing Spheres without gray
  areas represent metal atoms. Spheres with gray
  areas are non-metal atoms. Metal atoms give up
  their valence electrons to non-metal atoms.

(cont.)
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Ionic bonds

• Metal atoms lose electrons, makes them ()
• Non-metals gain electrons, Makes them (-)
• The charge difference creates the attraction
• A metal atom in an ionic bond will only lose 1-2
  atoms, makes a strong attraction with just a
  couple of neighboring atoms
• Produces weak overall bond strength, water can
  easily in between molecules

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Notes (cont.)

• Model 2 COVALENT NETWORK
• Properties
• Made entirely of nonmetal atoms
• Does not dissolve in water
• Does not conduct electricity
• Very hard solids
• Atoms have multiple valance electrons to use to
  bond
• Description of drawing Valence electrons connect
  atoms with each other in all directions like a
  grid or network.

(cont.)
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Notes (cont.)

• Model 3 MOLECULAR COVALENT
• Properties
• Made of nonmetal atoms
• Some dissolve in water, some do not
• Do not conduct electricity
• Tend to be liquids or gases or softer solids
• Description of drawing Valence electrons are
  shared between some atoms. This creates small
  stable units within the substance.

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Notes (cont.)

• Model 4 METALLIC
• Properties
• Made entirely of metal atoms
• Do not dissolve in water
• Conduct electricity
• Bendable solids
• Description of drawing Valence electrons are
  free to move throughout the substance like a
  sea of electrons.

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Metallic bond

• The attraction between metal atoms in an metal
  object
• Metals will generally have 1-4 electrons in their
  outer shell
• These are fairly easily released
• The released electrons form a sea swirling
  around the atoms.
• These electrons can move from place to place in
  the sea
• Electrons can possess energy, corresponds with
  the movement of electricity in an object

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Are there substances that do not seem to fit into
a model?

• List them and explain

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Answer To questions

• Sugar (Molecular Covalent)
• Au (metallic), KI (Ionic), He (None, why?)
• C02 (molecular covalent)
• 2) Non-metal atom have negative charge because
  they have an extra electron
• Metal atom have a positive charge because
  they have one less electron

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Answers

• 1) No2 (g) is molecular covalent
• 2a) hair gel molecular covalent
• 2b) silver bracelet metallic
• 2c) motor oil molecular covalent
• 2d) sodium bicarbonate ionic
• 3a) zinc metallic
• 3b) propane molecular covalent
• 3c) calcium carbonate ionic

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Answers to questions

• 3) The spherical atoms would have a positive
  charge because some of their electrons are in the
  sea
• 4) Difference is that in covalent network, each
  atom is sharing electrons with more than one
  other atom

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Answers to questions

• 5) a) molecular covalent are not glued tightly to
  all nearby atoms, allows greater freedom of
  movement
• b) ionic substance are brittle, because they do
  form strong bonds to only 1-2 nearby atoms, not
  with all nearby atoms.

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Answers to questions

• 6) The bonds occurs in all directions between a
  lot of atoms, but is not strong.
• But not every atom is bonded to all neighboring
  atoms
• They are adjustable, flexible

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Answers

• 7) Covalent bonds have atoms sharing electrons
  with many neighboring atoms
• Creates a strong bond in many directions
• Carbon shares 4 electrons with its neighbors,
  creating a strong bond in a plane of atoms

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Question 8

• Sugar does not have the metal electrons to
  produce metallic or ionic bonding
• Their atoms will form molecular covalent bonds
• Ionic materials will conduct because metal atoms
  are freed when ionic compounds are put into
  water.
• They can then combine with other metals to allow
  electrons to flow (electricity)

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Question 8

• Both sugar and salt dissolve in water, but salt
  solution conducts electricity while a sugar
  solution does not.
• Use the models to explain how these two
  substances might be bonded differently.

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Relate Bonding to Properties
Dissolves and Conducts IONIC Dissolves but does not conduct Molecular Covalent
Does not dissolves, but does conduct Metallic Does not dissolve or conduct Covalent

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Types of atoms
Made out of only metal Metallic Made out of only non-metal atoms Covalent and Molecular Covalent
Made from a combination of metal and non metal Ionic There are a few exceptions
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Making sense

• Given a compounds formula, Can you indicate the
  following
• Bond type, Solubility, Conductivity, degree of
  flexibility (bendable or brittle)
• Try Cu(NO3)2 (aq)
• C6H12O6 (aq)
• AgAu (s)

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Cu(NO3)2 (aq) C6H12O6 (aq) AgAu (s)
Bond type Ionic Molecular Covalent Metallic
Solubility very very not
Conductivity conductive Not conductive Conductive
Flexibility Brittle More flexible Most flexible
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Bonds

• Covalent bonds form from electrons being shared
  by atoms
• Ionic bonds are formed by the permanent transfer
  of electrons
• Metallic bonds are formed by the temporary
  movement of electrons between atoms

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Check in

• One of the first things we did in this class is
  make a golden penny by combining copper with
  zinc to make brass.
• How would you classify the bonding in brass?

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Wrap-Up

• A chemical bond is an attraction between atoms
  involving the valence electrons.
• There are four types of bonds ionic, extended
  covalent, molecular covalent, and metallic.

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Dissolves
Notes (cont.)
Yes
No
Conducts
Conducts
Yes
Yes
No
No
NaCl salt CuCl2 calcium chloride CuSO4 copper sulfate H2O water C12H22O11 sugar C2H6O ethanol Au gold Cu copper Al aluminum SiO2 sand C20H42 paraffin
Ionic
Molecular Covalent
Metallic
Covalent Network
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Notes (cont.)
Metal atoms
Non-Metal atoms
Metal Non-Metal atoms
Covalent Network
Molecular Covalent
Metallic
Ionic
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Check in

• One of the first things we did in this class is
  make a golden penny by combining copper with
  zinc to make brass.
• How would you classify the bonding in brass?