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CHAPTER 4

CHAPTER 4. Heat and Temperature. Misconception about Matter. Greeks, including Aristotle, did not believe that matter is made up of small particles called “atoms”. They believed that matter is “continuous” and has no space in it. Galileo and Newton believed otherwise.

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CHAPTER 4

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  1. CHAPTER 4 Heat and Temperature

  2. Misconception about Matter • Greeks, including Aristotle, did not believe that matter is made up of small particles called “atoms”. • They believed that matter is “continuous” and has no space in it. • Galileo and Newton believed otherwise.

  3. Kinetic Molecular Theory • Matter is mad up of small particles called “atoms”. • Atoms are neither created, divided or destroyed during any type of chemical or physical change. [ Law of Conservation of Matter]

  4. Atoms  Elements  molecules  Compounds • Every Element is made up of its own kind of atom. Different elements are made up of different atoms. • Molecules are made up of elements. • Molecule – is the simplest unit of a compound.

  5. 7 Diatomic Elements • Compounds – are pure substances • Mixtures – combinations of diff. compounds

  6. Phases of Matter • Solid – have definite volume • Liquid – have definite volume but no definite shape • Gas – have no definite volume and no definite shape • Plasma – have same property as gases but conduct electricity and interact strongly with magnetic fields

  7. Effects of Temperature • Converts compounds from one phase to another • Thermometer • Fahrenheit  Celcius  Kelvin conversion • Absolute zero = -273.15 oC = lowest temperature possible = molecules do not move at all

  8. Heat • Is the measure of the internal energy that has been absorbed or transferred from one body to another • Internal Energy – is the total kinetic and potential E of molecules of an object • External Energy – is the total kinetic and potential E of everyday-sized objects

  9. Units of Heat • calorie – the amount of E needed to raise the temp. of 1 gram of substance 1 oC. • Kilocalorie - the amount of E needed to raise the temp. of 1 kilogram of substance 1 oC. • BTU – (British Thermal Unit) - the amount of E needed to raise the temp. of 1 lb. of substance 1 oF.

  10. Law of Conservation of Energy • When an object gives off energy, something must absorb it. • Heat = q • Giving off heat = -q • Absorbing heat = + q • Note: +q = -q

  11. Specific Heat • Specific Heat (C) - the amount of heat needed to raise the temp. of 1 gram of substance 1 oC. • Compounds or Elements with high specific heat take awhile to heat up, but also take awhile to cool down. • Heat = mass of compound x C x change in Temp • q = mCDT

  12. Ways for Heat to Flow • 1. Conduction – transfer of E from molecule o molecule • - transfer of E from higher Temp. to lower Temp • - happens primarily in solids

  13. 2. Convection – transfer of heat by large-scale displacement of molecules with high KE • - Increased KE is transferred from molecule to molecule • - happens primarily in liquids and gases • - warm air is pushed to the top by cooler, more dense air and keeps being displaced by newly warmed air. As air cools, it sinks to the bottom.

  14. 3. Radiation – heat transfer due to temperature difference. • - involves radiant E, which is the E that moves through space (includes visible light which is given off when objects are heated at a certain temperature)

  15. Net Transfer of E when Temperatures are Different • All objects above Absolute Zero absorb and emit radiant E. • A hot object emits radiant E more than it absorbs radiant E. • A cold object absorbs more radiant E than it emits radiant E.

  16. Different Phase Changes • Need Heating • Sublimation: solid  gas. • Vaporization: liquid  gas. • Melting or fusion: solid  liquid. • Need Cooling • Deposition: gas  solid. • Condensation: gas  liquid. • Freezing: liquid  solid.

  17. 3 Laws of Thermodynamics • 1st Law – Law of Conservation of Energy • 2nd law – The entropy of disorder of the universe is always increasing. • 3rd law – The entropy or disorder of a crystal at Zero Kelvin is zero. (Atoms do not move at absolute zero!)

  18. Forms of Energy • Electromagnetic radiation wavelength, frequency and speed • Light • Heat

  19. Electromagnetic Spectrum • Radio Waves • Microwaves, Radar Rays • Infrared • Visible • UV • X-rays • Gamma Rays

  20. The Wave Nature of Light

  21. The Wave Nature of Light

  22. CHAPTER 8 TOPICS • Parts of the Atom • Rutherford vs. Bohr • Periodic Table • Metals/ Metalloids/Non-Metals • Isotopes • Ions and Charges • Forming Compounds

  23. Parts of the Atom • 1. Proton (+) • 2. Electron (-) • 3. Neutron (-)

  24. Chemistry in Color • Specific elements give color when heated in flame. • Continuous spectrum - e.g., rainbow • Line Spectrum

  25. Line Spectra • Held the key to the structure of the atom!

  26. The Bohr Atom • Bohr:suggested that electrons were responsible for the line spectra. Proposed that electrons traveled around the nucleus of the atom in shells

  27. The Bohr Atom • Bohr:associated each shell w/ a particular energy level. The farther away, the higher the Energy. Allowed electrons to jump from one shell to another. (ground state excited state)

  28. Comparison • Bohr Model similar to model for solar system where the planets revolve in their particular orbits. • Difference: Electrons can jump from one shell to another. The planets do not!

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