heat – thermal energy
DESCRIPTION
Heat – Thermal Energy. ISCI 2002. What is Heat?. Place your finger on the handle of a ‘hot’ pan. Ouch! Heat is energy that is transferred from one ‘system’ to another (two systems have different temperatures). Heat transferred to atoms and molecules – increases the KE of each. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/1.jpg)
Heat – Thermal Energy
ISCI 2002
![Page 2: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/2.jpg)
What is Heat?• Place your finger on the
handle of a ‘hot’ pan. Ouch!
• Heat is energy that is transferred from one ‘system’ to another (two systems have different temperatures).
• Heat transferred to atoms and molecules – increases the KE of each
![Page 3: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/3.jpg)
What is Heat? • Heat – another
form of energy
• Energy transmitted by electromagnetic waves– Sun – Infrared radiation – Energy conversions
• Units of heat:– Calorie (cal) – Joule (J)
![Page 4: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/4.jpg)
Laws of Thermodynamics • Thermodynamics – “movement of heat”
• Thermal energy transfers as heat – no net loss or gain – 1st Law of Thermodynamics
• When heat flows into or out of a system, the gain or loss of thermal energy equals the amount of heat transferred.
• Heat spontaneously flows from higher to lower substances, never from lower to higher temperature substances– 2nd Law of Thermodynamics
![Page 5: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/5.jpg)
Energy Conversion
![Page 6: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/6.jpg)
KE and Temperature • KE – Temperature
Relationship
• Temperature is the ‘average’ KE of all atoms and molecules in a system.
• Scales – Fahrenheit – Celsius – Absolute Zero
![Page 7: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/7.jpg)
Heat, Temperature, Mass and the Specific Heat of a Substance
Both beakers contain 1.0 kg of water
Same amount of heat applied
Rise in temperature will be exactly the same.
![Page 8: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/8.jpg)
Heat, Temperature, Mass and the Specific Heat of a Substance
What if you apply the same amount of heat, but double the volume in one beaker?
Left – 1.0 kgRight – 2.0 kg
![Page 9: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/9.jpg)
Heat, Temperature, Mass and the Specific Heat of a Substance
Volumes are 1.0 kg, but on the right is ethyl alcohol
Ethyl alcohol’s temperature will rise twice as fast as the temperature of the water.
![Page 10: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/10.jpg)
Putting it All Together
![Page 11: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/11.jpg)
Phase Changes of Water and Heat A – B : Ice temperature rising to 0 B – C : Ice temp remains at 0 even though heat constantly added; needed to change solid to liquid. Amount of heat need is called heat of fusion
C – D : temperature rises from 0 to 100 C no phase changes occur; only raising temp of water
D – E : At 100 C phase change occurs; amount of heat needed to do this is called heat of vaporization
![Page 12: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/12.jpg)
Thermal Expansion • As heat is transferred through a substance
– Molecules move faster; move far apart
• Liquids expand more than solids
• Engineering Applications – Bridges, Concrete, etc.
• Water expansion – Expands except in 0-4 C range – Occupies greater volume in this range; ice less
dense than water – Freezing increases water’s volume (decreases
density)
![Page 13: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/13.jpg)
Heat Transfer
• Conduction
• Convecti
on • Radiatio
n
![Page 14: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/14.jpg)
Radiation • Radiant Energy – Electromagnetic Waves
• Any substance above absolute zero emit radiant energy– f is proportional to T
• Humans emit ‘infrared’ radiation
• If a substance is real hot – emits light – 500 C (long waves – red light); 1200 C (white hot)
• Sun – emits short wave radiation; Earth emits longer wave radiation (terrestrial radiation) – cool surface
![Page 15: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/15.jpg)
Electromagnetic Spectrum
![Page 16: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/16.jpg)
Greenhouse Effect • How a real
greenhouse works– Glass and visible light – Traps ‘infrared’ sunlight
• Earth’s Greenhouse Effect– Carbon dioxide acts like
glass – Greenhouse gases– Allowed for life to
thrive
• Venus vs. Earth
![Page 17: Heat – Thermal Energy](https://reader036.vdocument.in/reader036/viewer/2022062301/5681308e550346895d966a83/html5/thumbnails/17.jpg)
Absorption of Radiation• Good emitters are good absorbers of
radiation
• A black object filled with hot water will cool faster. Why?