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 Total energy in molecules of a substance including  a) kinetic E of moving molecules  b) potential E stored in chemical bonds.

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Presentation on theme: " Total energy in molecules of a substance including  a) kinetic E of moving molecules  b) potential E stored in chemical bonds."— Presentation transcript:

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2  Total energy in molecules of a substance including  a) kinetic E of moving molecules  b) potential E stored in chemical bonds

3  Average kinetic energy per molecule  Average speed of molecule  KE = ½ m V 2 m = mass V = velocity  Velocity or speed is most important  0 velocity = absolute 0….no motion of particles

4  Flow of thermal Energy from hot to cold  Transfer of kinetic energy from one molecule to another  http://www.gcse.com/energy/images/conduction.gif http://www.gcse.com/energy/images/conduction.gif

5  1) Energy can not be created or destroyed  only converted from one form to another  or transferred from one place to another  2) Heat energy flows from high temperature areas to low temperature areas only

6  No net flow of heat energy because all areas are the same temperature  Heat flows from hot to cold until….  Thermal equilibrium is reached….  Then it just passes back and forth  Still moving so still heat!

7  Measure their own temperature  Put thermometer in water. Heat flows  Molecules of alcohol speed up and expand or  slow down and contract  Thermal equilibrium between thermometer and water causes red line to stop moving.  http://www.middleschoolchemistry.com/multimedia/chapter1/lesson3#heating_and_cooling_a_thermo meter http://www.middleschoolchemistry.com/multimedia/chapter1/lesson3#heating_and_cooling_a_thermo meter

8  Temperature is measured in…  o Celsius  Heat is measures in….  calories  1 calorie =  the amount of heat needed  to raise the temp of 1ml H 2 O  by 1 o C

9  The Calories in your food are Calories,  They are actually Kilocalories =  the amount of heat needed to warm up 1,000 ml of H 2 O by 1 o C

10  It takes more heat energy to increase the temperature of some substances.  We say those substances have a high specific heat.  Water has very High specific heat  Specific heat is measured in cal/ml/ o C  or cal/g/ o C

11  High specific heat warms up slower AND  Cools off slower  http://oceanservice.noaa.gov/education/pd/oceans_weather_climate/media/specific_heat.swf http://oceanservice.noaa.gov/education/pd/oceans_weather_climate/media/specific_heat.swf  More massive  http://mw2.concord.org/public/part2/he at/page2.cml http://mw2.concord.org/public/part2/he at/page2.cml

12  1) Conduction – objects touch, direct heat transfer from warm object to cold object  2) Convection – heat transferred by flowing molecules  3) Radiation – electromagnetic waves =  Infrared light waves  heat waves, not visible

13  Metals are good conductors because their  electrons are loosely held (can flow)  Non-metals hold their electrons tightly so are poor conductors called…  insulators

14  Good conductors at room temperature feel:  cold to the touch because….  heat is leaving your hand quickly.  Poor conductors don’t feel as cold because heat is leaving more slowly

15  warm, fast moving molecules rise carrying heat with them  (they expand & become less dense)

16  Electromagnetic waves  =light waves  Not visible  Heat waves

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18  Lowest energy = solid  a) strongest intermolecular forces  b) molecules vibrate in place so  definite shape and volume  Medium energy = Liquid  a) weaker intermolecular forces allow  molecules to flow around each other  so no definite shape  b) still to low energy for molecules to  break away completely and expand  so definite volume

19  Highest energy = gas  a) weakest intermolecular forces  b) molecules can flow & expand  c) no definite shape or volume

20  Change in amount of thermal energy cause molecules to move in different ways  Higher energy =  weaker intermolecular forces  as molecules expand  Mass does not change  Density changes

21  Solid  Liquid  Gas  low high  x = Heat energy (per mole) needed  to be in that phase

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23  A-B  Warming ice  Add E, Temp  B-C  Melting  Add E, no ∆ Temp  E used to break intermolecular forces so molecules can flow

24  C-D  Warming water  Add E, Temp  D-E  vaporization  Add E, no ∆ Temp  E used to break intermolecular forces so molecules can expand

25  Boiling  Bubbles of gas form at bottom of liquid  Evaporation  High energy molecules break loose from surface of fluid

26  F-E  Cooling steam  Remove E, Temp  E – D  condensing  Remove E, no ∆ Temp  Loss of E lets intermolecular forces reform & hold molecules together

27  D-C  Cooling water  Remove E, Temp  C-B  freezing  Remove E, no ∆ Temp  Loss of E strengthens intermolecular forces so molecules can only vibrate


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