CHAPTER 4 Heat and Temperature. Misconception about Matter Greeks, including Aristotle, did not...

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!