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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.
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]
• 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.
• 7 Diatomic Elements
• Compounds – are pure substances
• Mixtures – combinations of diff. compounds
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
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
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
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.
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
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
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
• 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.
• 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)
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.
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.
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!)
Forms of Energy
• Electromagnetic radiation wavelength, frequency and speed
• Light
• Heat
Electromagnetic Spectrum
• Radio Waves• Microwaves, Radar Rays• Infrared• Visible• UV• X-rays• Gamma Rays
The Wave Nature of Light
The Wave Nature of Light
CHAPTER 8 TOPICS
• Parts of the Atom• Rutherford vs. Bohr• Periodic Table• Metals/ Metalloids/Non-Metals• Isotopes• Ions and Charges• Forming Compounds
Parts of the Atom
• 1. Proton (+)
• 2. Electron (-)
• 3. Neutron (-)
Chemistry in Color
• Specific elements give color when heated in flame.
• Continuous spectrum - e.g., rainbow• Line Spectrum
Line Spectra
• Held the key to the structure of the atom!
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
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)
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!