1 / 24

Chapter 16

Chapter 16. Thermal Energy and Heat. Thermal Energy and Matter. Heat: is the transfer of thermal energy from one object to another due to a difference in temperature Heat flows from: HOT  COLD Cold: losing heat energy Hot: gaining heat energy.

britanni-fields
Download Presentation

Chapter 16

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 16 Thermal Energy and Heat

  2. Thermal Energy and Matter • Heat: is the transfer of thermal energy from one object to another due to a difference in temperature • Heat flows from: HOT  COLD • Cold: losing heat energy • Hot: gaining heat energy

  3. Kinetic Theory- all matter is made of particle (atoms, molecule, ions). These particles are always in random motion. • Higher Temp = higher kinetic = faster motion

  4. Temperature: is how hot or cold an object is compared to some reference point • Examples: • Outside Temperatures • Temperature of buildings 70.0’F • Runoff Water Temp. 35-42’F • Body Temp. 98.6’ F

  5. Thermometer: tool used to measure temp. 3 different scales ‘C ‘F K • Mercury expands as the thermometer gains heat (UP) • Mercury contracts as the thermometer loses heat (DOWN) • Formulas pg 255 C  F, F C

  6. Thermal energy: depends on mass, temperature and phase of an object. • Thermal energy is caused by the movement of atoms and molecules (friction) • Mass: greater mass = greater thermal e. • More mass = longer to heat up & cool down • Temp. greater temp = greater thermal e. • Greater SpecificHeat = Greater thermal E

  7. Phase: depends on amount of thermal E. • Solid: • Liquid: • Gas: • Plasma: most heat energy

  8. The States of Matter, Molecular Stickiness, and Thermodynamicsitl.chem.ufl.edu

  9. Thermal Expansion: occurs because particles of matter tend to move faster and spread out as temperature increases • INCREASE HEAT = INCREASE SIZE • DECREASE HEAT = DECREASE SIZE • Ex. Joints in side walks (celotex), joints in bridges, thermostats in homes, Thermometer • Balloon Demo: expanded as we added heat

  10. Specific Heat: a physical property that describes how a substance absorbs heat • Different substances absorb heat at different rates • The lower a material’s specific heat, the more its temp. will increase as heat is added. (heats & cools faster) • Metals: low specific heat • Nonmetals: high specific heat

  11. Specific Heat of Common Materials • Water = 4.18 J/g-’C • Plastic = 1.8 to 2.1 J/g-’C • Air = 1.01 J/g-’C • Iron = .449 J/g-’C • Silver = .225 J/g-’C

  12. Measuring Heat Changes • Calorimeter: is an instrument used to measure changes in a material’s heat • Closed container that holds water, thermometer, stirring rod • Used to calculate specific heat • Used to calculate # of calories in food • Picture on next slide and in book

  13. http://www.agro.cmu.ac.th/department/fe/equip • http://www.agro.cmu.ac.th/department/fe/equip_file/031_1.jpg http://www.agro.cmu.ac.th/department/fe/equip_file/031_1.jpg http://research.chem.psu.edu/mallouk/ilab/models.html

  14. 16.2 Heat & Thermodynamics • There are 3 ways that thermal energy is transferred from one object to another • Conduction • Convection • Radiation

  15. Conduction: is a heat transfer when 2 objects are touching (direct contact) • There is NO transfer of matter • Conduction works fastest with: • Solids  Liquids  Gases • The particles of liquids and gases are farther apart than solids, therefore heat is not transferred as quickly

  16. Thermal Conductors: are materials that allow heat and electricity to pass through them easily • Metals • Copper wire for electrical circuits, gold wire in spaceships, pots & pans • Low specific heat values

  17. Thermal insulators: are materials that DO NOT allow heat and electricity to pass through them easily • Non-metals • Wood, plastic, air, glass, fiberglass • Protect items from heat and electricity • High specific heat values

  18. Convection: heat transfer that takes place in fluids (liquids and gases) • HOT AIR/WATER RISES • Convection Currents: currents in liquids or gases, these currents transfer thermal energy (caused by difference in density) • Ex. Pavement, beaker of hot water, ocean currents, weather patterns, wind

  19. Radiation: is the transfer of thermal energy (heat) by waves through space • Radiation happens through air and empty space • Ex. Sun, wood burning stove, fireplace, candles • All objects radiate thermal energy

  20. 1st Law of Thermodynamics: states that thermal energy is conserved • Heat energy can’t be created nor destroyed • Heat energy can only be transferred and converted

  21. 2nd Law of Thermodynamics: states that heat CAN flow from COLDER objects to HOTTER objects, ONLY if work is done. • Ex. refrigerator, freezer, A.C. • Freon: refrigerant liquid/gas that is used in the cooling process (cars)

  22. ENTROPY: • The measure of how dispersed the energy is.

  23. 3rd Law of Thermodynamics: states that absolute zero CAN’T be reached • Absolute Zero: is the coldest possible temperature where molecular (atoms) motion stops • Absolute Zero = 0 K

  24. Using Thermal Energy • Heating Systems: • Forced-air: fuel heats air and fan pushes through the building. Cold air returns • Radiator:hot water or steam heat through radiation to the air. Uses a boiler to heat water • Electric: electricity heats coils in floor or ceiling by conduction.

More Related