Bellwork

1
Bellwork

• Which of the following
• represents a mixture?
• a piece of copper wire
• oxygen in a pressurized tank
• a slice of mushroom pizza
• a lead fishing weight

2
Chapter 13 Review

• Matter anything that has mass and takes up
  space
• Mass the amount of matter in something
• Volume the amount of space something occupies
• Which of the following is matter?
• A car?
• A box?
• You?

3
What is a property?

• A Property is a characteristic of a substance
  that can be observed.

4
Physical Property
A physical property is one that can be observed
without changing the identity of the substance.
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Examples

• Malleability the ability to be hammered into a
  thin sheet
• Ductility the ability to be stretched into a
  wire
• Melting/freezing point
• Boiling point
• Density
• Solubility
• Specific heat the amount of heat required to
  heat a substance 1 degree Celsius
• Luster shiny, matt

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Special Physical Properties

• Melting point the temperature at which a
  substance changes from a solid to a liquid at a
  given pressure
• water 0oC
• Boiling point the temperature at which a
  substance changes from a liquid to a gas at a
  given pressure
• water 100oC

7
Density

• Density is the amount of mass per unit of volume.
• Like many other properties it can be used to
  identify a substance.
• The density of water is 1.0g/mL

8
Calculating Density

• D m/V g/mL g/cm3
• Ex A cube has a mass of 2.8 g and occupies a
  volume of 3.67 ml. Would this object float or
  sink in water?
• Mass 2.8 g Volume 3.67 mL
• D 2.8g/3.67 mL 0.76 g/mL

9
Identification by Density

• A liquid has a mass of 25.6 g and a volume of
  31.6 mL.
• Use the table below to identify the substance.

M25.6 g V31.6 mL D 25.6 g/31.6 mL
D 0.81 g/mL The substance is ethanol.
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Chemical Properties

• A Chemical property is a property that can
  only be observed by changing the identity of the
  substance

• Examples
• flammability
• ability to rust
• reactivity with vinegar

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Element

• An element is a pure substance that cannot be
  broken down into any other substance by chemical
  or physical means.

• Examples
• aluminum
• zinc
• oxygen

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Atom

• Elements are comprised of atoms, which are so
  small they cannot be seen even with a microscope.

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Molecule

• Atoms bond together chemically to form
  molecules.

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Compound

• A compound is a pure substance made of 2 or
  more elements chemically combined in a set ratio.
  Compounds cannot be easily separated.

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Mixture

• A mixture is a pure substance made of 2 or
  more elements, compounds, or both, that are
  together yet not chemically bonded and therefore
  can be separated by physical means.

Heterogeneous Homogeneous
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Changes

• Physical change substance maintains its
  chemical makeup
• Ex state changes, dissolving
• Chemical change substance becomes something else
  entirely
• Ex burning, oxidation

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Chemical Reactions

• Endothermic reactions must absorb heat/energy in
  order for the reaction to take place.
• This intake of energy may be observed as a
  decrease in temperature as the reaction proceeds.
  
• Exothermic reactions release heat from the
  reaction.

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Chemical Reactions

• Reactants are the chemicals that go into a
  reaction.
• Products are the chemicals products that are
  created by the reaction.

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Law of Conservation of Matter

• States that the
• Mass of the reactants
• Mass of the Products
• (in a closed system)
• Ex 5 g of sodium(Na) 5 g of chloride (Cl)
  yields 10g of table salt (NaCl)

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Conservation of Matter Lab

• Objective
• To demonstrate the Law of Conservation of
  Matter by reacting vinegar baking soda in a
  closed system.

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Bellwork

• What is the difference between a compound
  and a mixture?

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Venn Diagram
23

• ENERGY!

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2 Main Types of Energy
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Temperature Energy
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Temperature
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Law of Conservation of Matter

• States that the
• Mass of the reactants
• Mass of the Products
• Also stated as matter cannot be created nor
  destroyed only transformed.

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Law of Conservation of Energy

• Energy also cannot be created nor destroyed
  only transformed or transferred.

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Law of Conservation of Energy
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Exothermic
Produces Heat
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Endothermic
Soaks up heat from the surroundings observed
as a decrease in temperature
25 ml citric acid soln 15 g baking soda
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Bellwork

• Which pure substance is composed of more
  than one element?
• - carbon
• - gold
• - water
• - sodium

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Intro.

• The PERIODIC TABLE contains information about
  the different ELEMENTS that make up all the
  solids, liquids, and gases in the known universe.

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Natural vs. Synthetic

• The majority of the known elements are
  naturally occurring, however all elements above
  92, are known as SYNTHETIC elements having been
  created in a lab.

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Atoms

• Elements are one or more identical ATOMS and
  each element has its own unique atom that looks
  different than all the other elements.

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Organization

• Elements are organized on the periodic table
  by their ATOMIC NUMBER, which is the number of
  PROTONS in the nucleus.

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Isotopes

• Atoms of the same element can have different
  numbers of NEUTRONS the different possible
  versions of which are called ISOTOPES.

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Calculate of Neutrons

• To determine the average number of neutrons
  in an element Round the atomic mass to the
  nearest whole number and subtract the atomic
  number (of protons). Ex K 39 19 20 neutrons.

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Atomic Mass

• The ATOMIC MASS listed on the periodic table
  is an average of the mass of all known isotopes
  of that element.

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Symbols

• Hg Mercury
• Au Gold Pb Lead
• Sn Tin Ag Silver
• Cu Copper Fe Iron
• K Potassium Na - Sodium

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Patterns in the Table

• The PROPERTIES of an element can be
  predicted by their location on the periodic table.

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Group 1

• Alkali Metals do not occur uncombined in
  nature highly chemically reactive

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Group 2

• Alkaline Earth Metals also do not occur
  uncombined good conductors

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Groups 3-12

• Transition Metals also good conductors
  form colorful compounds that last a long time
  since they are not highly chemically reactive

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Lanthanides

• Soft, shiny, malleable metals with high
  conductivity

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Actinides

• Most are synthetic and the nuclei are
  unstable (meaning they break apart quickly)

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Metalloids

• Along the stair step line
• (7) METALLOIDS that have properties of
  metals and non-metals are very useful for their
  varying abilities to conduct electricity (i.e.
  silicon semi-conductors in computer chips).

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Non-Metals

• The NON-METALS are not good conductors but
  they combine with others readily to form
  compounds.
• Many of these elements are crucial in
  creating and maintaining life (C, N, O, P, S).

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Group 17

• HALOGENS - meaning salt forming
• They are DIATOMIC, meaning they never exist
  as a single atom.

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Group 18

• NOBLE GASES do not bond with other
  elements at all, hence why they are called noble

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Bellwork

• The element silicon is best used for which
  purpose?
• - as a container to keep coffee hot
• - as a semiconductor in a computer chip
• - as a material to make airplane frames
• - as a malleable material for coins and
  jewelry

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Protons Electrons

• Atoms are in general NEUTRAL since they
  generally have the same number of protons as
  electrons in their pure form. They strive at all
  times to maintain their neutrality.

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Electrons

• We know already that ELECTRONS are orbiting
  around the nucleus of the atom. Where they are
  orbiting helps us to make some predictions about
  how and if an element will combine with other
  elements (reactivity).

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Energy Levels

• There are several ENERGY LEVELS within the
  electron cloud and each can only hold a certain
  number of electrons.
• The period/row on which an element can be
  found will tell you how many energy levels there
  are in an atom of that element.

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Filling the Energy Levels

• 1st energy level holds 2 electrons
• 2nd energy level holds 8 electrons
• 3rd energy level holds 18 electrons
• There are 7 energy levels in total but we
  will only concern ourselves now with the first 18
  elements so we will only need to know about the
  first 3.

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Valence Electrons

• Not all energy levels will be filled and the
  electrons that reside in the outermost energy
  level are called the VALENCE ELECTRONS.
• You can find out at a glance how many
  valence electrons an element has by looking at
  the group number.

57
Bell Work

• How can a scientist, using the periodic
  table, find an element with properties similar to
  another element?
• - by comparing density
• - by finding its periodic group
• - by comparing malleability
• - by comparing atomic weight

58
Bell Work

• Which periodic group does the element
  chlorine belong to?
• - alkali metals
• - alkali earth metals
• - noble gases
• - halogens

59
Bell Work

• How would you calculate the number of
  neutrons in an atom of a given element?

60
Bell Work

• What is the NAME of the family/group that
  fluorine belongs to?

61
Bell Work

• What is the NAME of the family/group that
  Potassium belongs to?
• Dont forget to have your completed Periodic
  Table from yesterday out when I come around with
  the stamp ?

62
Bell Work

• Which of the following correctly
  compares the elements on the right side of the
  periodic table with the elements on the left?
• - The elements on the right side are generally
  denser than the elements on the left side.
• - The elements on the left side are better
  conductors of electricity than the elements on
  the right side.
• - The elements on the right side are better
  conductors of thermal energy than those on the
  left side.
• - The elements on the left side have lower
  melting point than the elements on the right
  side.
• Dont forget to have your completed homework
  out?

63
Bellwork

• Which element is LEAST likely to combine
  with another element to form a molecule?
• Chlorine (Cl), a halogen
• Iron (Fe), a metal
• Neon (Ne), a noble gas
• Silicon (Si), a metalloid

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Molecules

• 2 or more atoms help together by chemical
  bonds

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Valence Electrons

• Are the electrons on the outermost shell of
  an atom that participate in bonding.

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Lewis Dot Structures

• Diagrams that show electrons, bonding, and
  lone pairs of electrons.

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Covalent Bonds

• A chemical bond that involves the SHARING of
  their valence electrons.

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Ionic Bonds

• A bond that involves the TRANSFER of valence
  electrons from one atom to another.

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Ions

• Atoms that gain or lose electrons, therefore
  having a charge.

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Cations

• Atoms with a positive charge. These are
  metals since they lose electrons because they
  have one or 2 to spare.

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Anions -

• Atoms with a negative charge. These are
  nonmetals since they gain electrons because they
  only need 1 or 2 to become stable.

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Ionizing Energy

• The amount of energy required to remove an
  electron from an atom.

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Bellwork

• What do these chemicals have in common?
• Cu SO4 ZnCl4 Fe2O3
• Number of atoms
• Presence of oxygen
• Presence of metal
• Number of bonds

74
Bellwork

• You have a sample of an unknown element.
  At room temperature, this element is a gas
  reacts easily with other elements to form
  compounds. In which column of the periodic table
  does this element most likely belong?
• - IIA
• - VA
• - VIIA
• - VIIIA

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Chemical Reactions

• Chemical change occurs when bonds break and
  new bonds are formed.
• The chemical composition (makeup) of the
  substance(s) has been altered.

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Evidence of Chemical Change

• Change of properties
• heat absorbed -endothermic
• heat released exothermic
• gas formation (O2, CO2)
• Precipitate formation

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Chemical Equations

• Reactants ? Products
• 2H2 O2 ? 2H20
• Coefficient of molecules
• Subscript - of atoms

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Types of Chemical Reactions

• Synthesis
• A B ? C
• Decomposition
• C ? A B
• Replacement
• AB CD ? AD BC

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Conservation of Mass

• Mass of Reactants
• Mass of Products

Remember the lab where we reacted baking soda and
vinegar and trapped the CO2 in the balloon!
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BellWork

• Five molecules of methane contain five carbon
  atoms and 20 hydrogen atoms. What is the
  chemical formula of methane?
• CH4
• C2H8
• C4H20
• C5H20

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Activation Energy

• Activation Energy is the minimum amount of energy
  required to start a chemical reaction.
• It has a cascading effect.
• An endothermic reaction requires A LOT of
  activation energy.

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Surface Area

• If you break the reactants into smaller pieces
  then there is more surface area in contact with
  the other reactant. Thereby increasing the
  chance that 2 oppositely charged atoms can bond
  together.

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Temperature

• If you increase the temperature then the
  molecules are moving faster and thereby making
  connections more frequently.

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Concentration

• Concentration is the amount of a substance in a
  given volume. Increasing the concentration of a
  substance means there are more atoms or molecules
  available for bonding.

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Catalysts

• Catalysts increase the rate of reaction by
  lowering the activation energy required to start
  the reaction.
• They are not reactants and they are not consumed
  during a reaction.

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Inhibitors

• Inhibitors slow reactions by interfering with the
  reactants ability to get to each other.

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Demo Time

• Decomposition of Hydrogen Peroxide
• KI
• 2H2O2 ? 2H2O O2

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Follow Up Questions

• Answer on a sheet of notebook paper
• Describe what happened in this demonstration.
• Is this an endothermic or exothermic reaction?
• What is a catalyst?
• Name the catalyst in this demonstration.
• Could it be included as a reactant in the
  chemical equation?

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Acids

• Produce H ions in H2O
• Ex HCl ? H Cl-
• Properties
• Tastes sour
• Corrosive reaction w/metal
• Reacts w/CO32- to make CO2
• Turns blue litmus paper red

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Examples of Acids

• HCl hydrochloric acid
• CH3CO2H acetic acid (vinegar)
• H2SO4 sulfuric acid
• Ascorbic Acid Vitamin C (citrus)
• Fertilizers
• Nitric Phosphoric Acid
• Lactic Acid

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Bases

• Produce OH- ions in H2O
• Ex NH3 H2O ? NH4 OH-
• Tastes bitter
• feels slippery
• Turns red litmus paper blue

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Examples of Bases

• NaHCO3 baking soda
• household cleaners including
• NH3- ammonia
• Drain Cleaner

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Strength

• The strength of an acid or a base is based on how
  well it produces ions in water.
• Strong Acids HCl H2SO4
• Strong Bases - NaOH

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Measuring Strength

• pH Potential Hydrogen
• Range of values from 0 to 14 that describes the
  concentration of H ions in a substance.
• Since we are measuring H ions and they are
  produced by acids, we can expect the higher it is
  on the scale, the more acidic it is!

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Safety

• Know the pH (strength) of the acid or base you
  are handling.
• Everything from 2-11 is in the safe zone.

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Precautions

• When working with a strong acid or base (0-2 or
  11-14) be sure to wear goggleseven if its a
  dilute solution!
• For spills-
• Pour vinegar on a base sodium bicarbonate on an
  acidbecause

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Acid Base Neutralization

• Displacement reaction
• Acid Base ?
• (liquid) water (solid) salt
• Salt Group 1-2 Metal a halogen

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Demo Time
NaHCO3 NaOH ? Na2CO3 H2O
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Precipitate Reactions

• If the ions in 2 solutions combine to form a
  solid and that solid is NOT soluble with the
  solvent produced a precipitate will form.
• ? Example
• Fe(NO3)3(aq) 3 NaOH(aq) ? Fe(OH)3(s) 3
  NaNO3(aq)

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Demo Time

• Cu(NO3)2(aq) 2 NaOH(aq) ? Cu(OH)2(s) 2
  NaNO3(aq)