1 / 12

Heat Energy

Heat Energy. Thermal Energy Conversions. I. Conduction -. Transfer of thermal energy by direct contact Always from a solid hot object to a solid cold object Takes place in solid, liquid or gases

vbrunson
Télécharger la présentation

Heat Energy

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. Heat Energy

  2. Thermal Energy Conversions I. Conduction - • Transfer of thermal energy by direct contact • Always from a solidhot object to a solidcold object • Takes place in solid, liquid or gases • Example:A metal spoon inside a saucepan gets hot while a saucepan is getting heated. If you were the chef in this picture and had to stir the contents for 20 minutes non-stop while on high heat – which type of spoon would you want to use?

  3. Conductors • Transfer heat easily • more tightly packed the particles, the better it is as a conductor • Most often Metals-metal spoon, metal pan, copper, iron, steel, silver

  4. Insulators ·does not allow heat to move easily through them ·wood, plastic, glass, fiberglass, air, Styrofoam • double pane windows (air between 2 panes of glass)

  5. Insulation R-value-rates insulation (higher number best) R-1 R-16 R-20

  6. Energy Vocabulary • absorbers-take in the energy • reflectors-reflect the energy • emitters-good absorbers that release energy later • dark and dull materials absorb • light and shiny materials reflect

  7. Thermal Energy Conversions Continued II. Convection - • Transfer of thermal energy in fluids – anything that flows • Always between liquids and gases • Example: hot air balloon, wind, ocean & air currents, home heating, all the soup in a pot becoming warm • warmer fluids (less dense) rise, buoyant convection • cooler fluids (more dense) sink • wearing sweater keeps the heat from being taken away from the body

  8. Thermal Energy Conversions Continued III. Radiation - • Transfer of thermal energy through waves. • Electromagnetic waves-light, ultraviolet rays, x-rays, infrared rays • Travels though gas and no air (vacuum) (outer space) • Colors reflect waves differently. • Black absorbs, White reflects • Example: sun’s energy, microwaves and radio waves infrared light bulbs, person warmed by a fire .

  9. Specific Heat What is specific heat? • the amount of energy needed to raise 1 gram of a substance 1°C in temperature • the property of a substance that tells us how much the temperature goes up when a given amount of heat is added • the lower the specific heat number the quicker it heats up or cools down • water has a high specific heat, metals have a low specific heat • specific heat of water is always 1.00cal/g·C° • If in joules it is 4.2 J/g·C˚

  10. Formula to calculate specific heat: Heat gained or lost = Mass X Change in Temperature X Specific Heat Q = (m)(ΔT)(Cp) Q = heat gained or lost (calories or joules or BTUs) m = mass (grams) ΔT = change in Temperature in °C (final temp – initial temp) Cp = Specific Heat (cal/g°C) or (J/g·C˚)

  11. Formula Substitute Answer Calculating Specific Heat If the specific heat of copper (Cu) is 0.09cal/g°C, how much heat is needed to raise the temperature of 5 grams of copper by 10°C? Step 1 Read the problem. Draw a picture. Step 3 Set up the formula. Step 4 Substitute the numbers. Solve. Box Answer with units. Step 2 Write down what you know. What are you trying to find? Cp= 0.09cal/g°C M = 5g Q = (m)(ΔT)(Cp) Q = (5g)(10°C)(0.09cal/g°C) Q =4.5cal ΔT = 10°C 4.5cal Q =

  12. Do Problems 1 & 2 in Your Notes.

More Related