# CHAPTER 4 Heat and Temperature.

## Presentation on theme: "CHAPTER 4 Heat and Temperature."— Presentation transcript:

CHAPTER 4 Heat and Temperature

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 = 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

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 gave color when heated in flame. Continuous spectrum - e.g., rainbow Line Spectrum

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!