chapter 2: energy and matter “does energy really matter?” sept. 2006
TRANSCRIPT
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Chapter 2:Chapter 2: Energy and MatterEnergy and Matter
““Does energy really matter?”Does energy really matter?”
Sept. 2006
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Chapt. 2 ObjectivesChapt. 2 Objectives
• Learn the three basic forms of energy.• State the “Law of Conservation of Energy.”• Compare Fahrenheit, Celsius & Kelvin temperature
scales.• Explain what is meant by “Absolute Zero.”• Name & describe the four states of matter.• Compare the physical & chemical properties of matter.• State the “Law of Conservation of Matter.”• Explain the difference between elements & compounds.• Compare homogeneous and heterogeneous mixtures.• Describe techniques to separate mixtures.
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2-1 ENERGY2-1 ENERGY
• Energy is the capacity to do work or to produce heat.
• Forms of energy– Kinetic (motion)
– Potential (position, gravity, chemical, electrical)
– Radiant (infrared, ultraviolet, X-rays)
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Measuring EnergyMeasuring Energy
One calorie = Energy needed to raise 1 gram water by 1 degree Celsius
1,000. calories = 1 Calorie (food)
1.00 calorie = 4.182 Joules
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Law of Conservation of EnergyLaw of Conservation of Energy
• States that…– In any process, energy is neither created nor
destroyed, but…– …energy may be converted into other forms.
(Can you give any examples?)
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Chapt. 2 ObjectivesChapt. 2 Objectives• Learn the three basic forms of energy.• State the “Law of Conservation of Energy.”• Compare Fahrenheit, Celsius & Kelvin
temperature scales.• Explain what is meant by “Absolute Zero.”• Name & describe the four states of matter.• Compare the physical & chemical properties of
matter.• State the “Law of Conservation of Matter.”• Explain the difference between elements &
compounds.• Compare homogeneous and heterogeneous
mixtures.• Describe techniques to separate mixtures.
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2-2 TEMPERATURE2-2 TEMPERATURE
• Heat and temperature are not the same!– Heat is a form of energy.– Temperature is a measure of heat energy.
• Thermometers (invented by Galileo) measure temperature.
• Fahrenheit, Celsius or Kelvin scale?– SI scale is the kelvin (K) scale (no ° sign)– 1°C = 1 K– K = °C + 273– Water freezes at 273 K & boils at 373 K– Zero kelvin is known as “Absolute Zero.”
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What happens as energy is removed from matter?What happens as energy is removed from matter?
• Consider steam (water vapor) at 150°C (or 423 kelvins):– First it becomes a liquid (water). (100°C or 373 K)
• Water particles slow down & get closer together.– Liquid water continues to cool as energy is removed.
• Water particles continue to slow down.– Eventually it freezes to a solid (ice). (0°C or 273 K)
• Same thing continues to occur as more kinetic energy is lost.
• But as more energy is removed, what happens? – Temperature drops more, well below 0°C (or 273 K).
• Particles move more slowly (losing kinetic energy) until…• …at -273°C (or 0 K) motion stops! (Zero kinetic energy!)
– Zero kelvin is known as “Absolute Zero.”
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Absolute ZeroAbsolute Zero• Zero kelvin or -273°C• The temperature at which all motion
theoretically ceases.• Material at 0 K would have NO kinetic
energy.• Zero kelvin has not been reached, but
scientists have come very close to it.• Materials have very unusual properties at
Absolute Zero!
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ProblemsProblems
• Sheets 2-2A, 2-2PP, 2-2RR
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Chapt. 2 ObjectivesChapt. 2 Objectives• Learn the three basic forms of energy.• State the “Law of Conservation of Energy.”• Compare Fahrenheit, Celsius & Kelvin temperature
scales.• Explain what is meant by “Absolute Zero.”• Name & describe the four states of matter.• Compare the physical & chemical properties
of matter.• State the “Law of Conservation of Matter.”• Explain the difference between elements &
compounds.• Compare homogeneous and heterogeneous
mixtures.• Describe techniques to separate mixtures.
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2-3 What is “Matter”?2-3 What is “Matter”?
• “Matter” is anything that has mass and volume (that is, it takes up space).
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Categories to ConsiderCategories to Consider
• Matter
• Not Matter
• Not Sure
Words will appear on the slide. You decide the category to which they belong, and write it in your notebook (left side).
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The ListThe List• Soda Can• Water• Fish• Garbage• Time• Motion• Computer• Carbon Dioxide Gas• The Middle of a Full Balloon• An Idea• Tree• Energy
Jump Ahead
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MassMass
• The quantity of matter in an object.
• Measured in kilograms, kg (SI unit).
• Also measured in grams, g, for convenience in chemistry labs.
• Exactly 1,000 grams = 1 kilogram.
• A “Balance” measures mass, but a “Scale” measures weight. (What’s the difference?)
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WeightWeight
• The effect of gravity on an object.
• An object may be weightless, but it always has mass.– If you were hit by a moving brick while you
were deep in outer space, it would still hurt!
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VolumeVolume
• A derived unit that measures the amount of space an object occupies.
• Measured in cubic meters (m3 is SI Unit), but Liters (L) and milliliters (mL) are more commonly used in chemistry lab.
• 1 cm3 = 1 mL
• Exactly 1000 mL = 1 L.
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Properties of MatterProperties of Matter
• Electrical Conductivity - ability to carry an electrical current. (Copper)
• Heat Conductivity - ability to transfer thermal energy. (Steel)
• Density - “mass-to-volume ratio”; how tightly matter is packed. (Cement is very dense; air is not.)
• Melting Point – solid-to-liquid (or liquid-to-solid) change; same as freezing point.
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Properties of Matter (cont)Properties of Matter (cont)
• Boiling Point – liquid-to-gas (or gas-to-liquid change); same as condensation point.
• Malleability – able to be hammered, rolled or beaten into thin sheets. (Aluminum foil)
• Ductility - ability to be drawn into a wire. (Copper, tungsten)
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Properties of Matter (cont)Properties of Matter (cont)
– Physical• Can be observed
without changing the identity of the substance.
• Boiling & all phase changes, color, temperature, size.
• Chemical • Involve changing the
substance into a new substance.
• Flammability, rusting, digesting, aging.
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Intensive Intensive vsvs. Extensive Properties. Extensive Properties
• Intensive – a property that does not depend upon how much you have.
• Flammability, color, hardness, crystal shape, temperature.
• Extensive – a property that does depend upon how much you have.
• Volume, mass, height, weight.
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ProblemProblem
• “Observing a Candle” Experiment.
• Follow the procedure on page 70 very carefully.
• Be sure to list the physical & chemical properties of the candle (before, during & after the experiment).
• Record as many observations as you can!
• Note Part 5.
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Class Activity: Sorting MaterialsClass Activity: Sorting Materials
• Sort 20 materials listed on signs.• Column A has oxygen & neon.• Column B has apple & sand. • Where does iron go?• Where does water go?• Continue sorting the rest.• What are your criteria?• What definitions can we derive from this?
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Pure Substances vs. MixturesPure Substances vs. Mixtures
• A pure substance is matter that is uniform, has unique chemical and physical properties, and has a definite composition.– Elements– Compounds
• A mixture is a blend of two or more pure substances that are not chemically combined.– Homogeneous Mixtures– Heterogeneous Mixtures
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ElementsElements• An element is a substance that cannot be separated
into simpler substances by a chemical change.
• An atom is the smallest particle of an element that retains the chemical identity of that element.
• Element names are logical, often named after locations, discoverers or historical roots (Latin, German etc.).
• Over 110 elements; only 92 occur in nature.
• Chemists use symbols to abbreviate element names.– Written with one capital letter and possibly one lower case letter.– Example: “CONI” differs from CoNi, CONi, CoNI. (Why?)
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Elements to LearnElements to Learn
You must learn the names and correct chemical symbol for Elements 1 to 20 of the Periodic Table.
Also know Cr, Mn, Fe, Cu, Zn, Br, Kr, Ag, Sn, I, Xe, Au, Hg, Pb, W.
• Be able to give the name from the symbol and the symbol from the name.
• Practice and test yourself! (Flash cards?)
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Elements vs. CompoundsElements vs. Compounds
Recall that an element is a substance that cannot be separated into simpler substances by a chemical change.
But a compound is a substance containing two or more different elements combined in a fixed ratio. Examples: H20 and AlCl3
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MixturesMixtures
• A mixture is a blend of two or more pure substances that are not chemically combined.
• Heterogeneous mixtures have visibly different parts.– EXAMPLES?– Oatmeal raisin cookies, salad dressing
• Homogeneous mixtures do not contain visibly different parts.– EXAMPLES?– Salt water, air
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MIXTURETwo or more substances not
chemically combined.
MATTER
PURE SUBSTANCE
HETEROGENEOUSHOMOGENEOUS ELEMENTS COMPOUNDS
CLASSIFICATION OF MATTER
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MIXTURETwo or more substances not
chemically combined.
MATTER
PURE SUBSTANCE
HETEROGENEOUS HOMOGENEOUSELEMENTS COMPOUNDS
CLASSIFICATION OF MATTER
Separate by physical means?
YES NO
Uniform Composition?NO YES
Decompose by chemistry?NO YES
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ProblemProblem
• How would you separate a sample of sandy sea water from Surf City into all of its components?
• Devise a scheme in your notebook.
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Separating MixturesSeparating Mixtures
• Filtration– Example: making coffee
• Distillation– Example: boiling water
• Crystallization– Example: Salt Flats, UT
• Chromatography– Example: ink running when wet
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Did we meet the Chapt. 2 Objectives?Did we meet the Chapt. 2 Objectives?
• Learn the three basic forms of energy.• State the “Law of Conservation of Energy.”• Compare Fahrenheit, Celsius & Kelvin temperature
scales.• Explain what is meant by “Absolute Zero.”• Name & describe the four states of matter.• Compare the physical & chemical properties of matter.• State the “Law of Conservation of Matter.”• Explain the difference between elements & compounds.• Compare homogeneous and heterogeneous mixtures.• Describe techniques to separate mixtures.