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Title: 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!

4
Ch 1 TestsThe Science of Chemistry
Class Average Score (out of 60) Percentage
2A
4A
1B
3B
5
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.

6
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

7
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

8
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

9
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.

10
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

11
Endothermic/Exothermic Processes
  • Endothermic describes a process in which heat
    is absorbed from the environment
  • Examples
  • Ice melting
  • Water boiling

12
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

13
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.

14
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

15
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.

16
Conservation of Energy in a Chemical Reaction
Does this chart represent an exothermic or
endothermic process?
17
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

18
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

19
Energy Can be Released or Absorbed as Heat
  • Exothermic reaction
  • Energy is released as heat
  • Endothermic reaction
  • Energy is absorbed as heat

20
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.

21
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

22
To find C T(K) - 273 To find K t(C)
273
23
Transfer of Heat May Not Affect Temperature
Heating Curve for Water
24
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.

25
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)

26
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.

27
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.

28
Homework
  • Section 2.1 review, pg. 45 1-13
  • Phase Change Diagram worksheet
  • Homework Concept Review Energy
  • Next time Sec 2.1 Quiz
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