Monday, Sept. 28th:

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Friday, Sept. 20th A DayMonday, Sept. 23rd
B DayAgenda

• Ch 1 Tests
• Start Ch. 2 Matter and Energy
• Section 2.1 Energy
• Energy, physical/chemical changes, evaporation,
  exothermic/endothermic, law of conservation of
  energy
• Homework
• Pg. 45 1-13
• Phase Change Diagram WS
• Concept Review Energy
• Quiz over section 2.1 next time!

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Ch 1 TestsThe Science of Chemistry
Class Average Score (out of 60) Percentage
2A
4A
1B
3B
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Ch 2 Matter and EnergySec. 2.1 Energy

• Energy the capacity to do work, such as moving
  an object, forming a new compound, or generating
  light.
• Energy is always involved when there is a change
  in matter.

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Changes in Matter can be Physical or Chemical

• Physical change a change of matter from one
  form to another without a change in chemical
  properties.
• The chemical nature of the substance does not
  change.
• Examples
• Ice melting
• Water boiling

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Changes in Matter can be Physical or Chemical

• Chemical change a change that occurs when one
  or more substances change into entirely new
  substances with different properties.
• A chemical change occurs whenever a new substance
  is made.
• Example
• Reaction of hydrogen oxygen to produce water

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Every Change in Matter Involves a Change in Energy

• All physical AND chemical changes involve a
  change in energy.
• Sometimes, energy must be supplied for the change
  in matter to occur.
• Example
• for ice to melt, energy must be supplied so that
  the particles have enough energy to slide past
  one another

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Every Change in Matter Involves a Change in Energy

• If more energy is added to the melted ice and the
  boiling point is reached, the particles of the
  liquid will leave the liquids surface through
  evaporation.
• Evaporation the change of a substance from a
  liquid to a gas.

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Energy and Change

• Sometimes, energy is released when a change in
  matter occurs.
• Examples
• Energy is released when a vapor
• turns into a liquid (condensation)
• Energy is released when a liquid turns into a
  solid (freezing)
• Energy is released when hydrogen and oxygen
  combine to form water

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Endothermic/Exothermic Processes

• Endothermic describes a process in which heat
  is absorbed from the environment
• Examples
• Ice melting
• Water boiling

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Endothermic/Exothermic Processes

• Exothermic describes a process in which a
  system releases heat into the environment
• Examples
• Water freezing
• Water condensing into
• liquid from vapor
• Hydrogen oxygen form
• water

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Conservation of Energy

• Law of conservation of energy the law that
  states that energy cannot be created or destroyed
  but can be changed from one form to another.
• During any chemical or physical change, the total
  quantity of energy remains constant.

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Energy is Often Transferred

• To keep track of energy changes, chemists use the
  terms system and surroundings.
• System all of the components that are being
  studied at any given time
• Surroundings everything outside
• of the system

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Conservation of Energy in a Chemical Reaction

• An exothermic process involves a transfer of
  energy from a system to its surroundings.
• An endothermic process involves a transfer of
  energy from the surroundings to the system.
• The total energy of the systems and their
  surroundings remains the same.

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Conservation of Energy in a Chemical Reaction
Does this chart represent an exothermic or
endothermic process?
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Energy Can be Transferred in Different Forms

• The transfer of energy between a system and its
  surroundings can involve different forms of
  energy
• Chemical
• Mechanical
• Light
• Heat
• Electrical
• Sound

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Heat

• Heat the energy transferred between objects
  that are at different temperatures energy is
  always transferred from higher-temperature
  objects to lower-temperature objects until
  thermal equilibrium is reached.
• Kinetic energy the energy of an
• object that is due to the objects
• motion

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Energy Can be Released or Absorbed as Heat

• Exothermic reaction
• Energy is released as heat
• Endothermic reaction
• Energy is absorbed as heat

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Heat is Different From Temperature

• Temperature a measure of how hot or cold
  something is specifically, a measurement of the
  average kinetic energy of the particles in an
  object.

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Temperature is Expressed Using Different Scales

• The two temperature scales that are used in
  chemistry are
• Celsius, C
• Kelvin, K
• 0C freezing point of water
• 0 K absolute zero, the temperature at which
  the minimum average kinetic energies of all
  particles occur

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To find C T(K) - 273 To find K t(C)
273
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Transfer of Heat May Not Affect Temperature
Heating Curve for Water
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Transfer of Heat May Not Affect Temperature

• Notice that the temperature only increases when
  the substance is in the solid, liquid, or vapor
  states.
• The temperature does not increase when the solid
  is changing to a liquid or when the liquid is
  changing to a gas.
• The energy that is added is used to change state.

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Specific Heat

• Specific Heat the quantity of energy, as heat,
  that must be transferred to raise the temperature
  of 1 g of a substance 1 K or 1C.
• The SI unit for energy is the joule (J)
• Specific heat is expressed in
• joules per gram kelvin
• (J/g K)

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Specific Heat

• Metals tend to have low specific heats, which
  indicates that relatively little energy must be
  transferred as heat to raise their temperatures.
• Water has an extremely high specific heat.
• This is why a metal pot gets hot fast but the
  water inside it takes a long time to warm up.

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Specific Heat

• This is also why Lake Michigan is always so cold,
  even in August!
• It takes a long time to
• warm something, like water,
• that has a high specific heat.

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Homework

• Section 2.1 review, pg. 45 1-13
• Phase Change Diagram worksheet
• Homework Concept Review Energy
• Next time Sec 2.1 Quiz