1 / 10

Heat & Specific Heat

Heat & Specific Heat. Mr. Shields Regents Chemisty U03 L04. 70 deg C. 30 deg C. Heat. Let’s now discuss something called HEAT and HEAT CAPACITY. Heat is the energy transferred between particles and the surroundings as a result of a temp. difference.

zlata
Download Presentation

Heat & Specific Heat

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 & Specific Heat Mr. Shields Regents Chemisty U03 L04

  2. 70 deg C 30 deg C Heat Let’s now discuss something called HEAT and HEAT CAPACITY Heat is the energy transferred between particles and the surroundings as a result of a temp. difference It ALWAYS FLOWS from Hot to Cold. NEVER from Cold to hot! Ex. You put a cold pack on your leg. Heat flows from your leg to the cold pack. Your leg Loses heat so it “feels” cold. “COLD” DOES NOT FLOW FROM THE ICE PACK

  3. Heat Energy (Q) • Heat energy results from the movement of atoms & molecules in matter. • This Energy depends upon how much of the substance is present (an extensive property) • Remember the SI Unit for energy is the JOULE (calories are used in Eng. System) 1 calorie = 4.184 Joules and 1 calorie (or 4.184J) can raise the temp of 1g water 1°C

  4. Heat Flow • Remember …heat always flows from hotter objects to cooler objects. • And the Quantity of heat transferred depends on: • Temperature difference • Mass of both substances • And the SPECIFIC HEAT of both substances H C Hey! What’s this?

  5. Specific Heat • Some materials absorb or transfer heat better • than other materials. • Consider what happens to the temperature of a • metal spoon handle vs. a plastic spoon handle • immersed in a cup of hot coffee. We use cloth pot holders to pick up hot metal pots. We also use cast iron radiators (not plastic or wood) to heat our homes by running hot water through it.

  6. Also 1 cal The SPECIFIC HEAT of a substance is the amount of heat required to raise the temperature of 1 g of the substance by 1 degree centigrade. 1 deg (Cp) • Each substance has it’s own unique • specific heat (Cp)

  7. Specific heats of various Materials Materials with LOW Cp are Good heat Conductors  What material would make The best Radiator? Cu, Brass or Iron? Which material Is the best Heat Insulator? 

  8. Change in Temp Specific Heat Equations HEAT is typically represented by the term “q” Specific Heat is represented by the term “Cp” Recall that SPECIFIC HEAT of a substance is the amount of heat required to raise the temperature of 1 g of the substance by 1 degree C. Therefore …. q = m x Cp x (Tf – Ti) m = mass Tf = Final Temperature Ti = Initial Temperature

  9. Specific Heat Calculations Let’s try a problem. How much heat energy in Joules is needed to raise the temperature of 30 grams of water from 20 deg. C to 30 deg. C? Recall that q = m x Cp x (Tf – Ti) q = 30 g x 4.18 J/g deg C x (30 deg C – 20 deg C) q = 125.4 x 10 deg C = 1254 Joules

  10. Specific Heat Calculations Let’s try another problem. If 1500 joules are added 100 grams of water at 20 deg C what is the final temperature of the water? Heat = mass x specific heat x (final temp – initial temp) q = m x Cp x (Tf – Ti) • 1500 = 4.18 J/g deg C x 100 g x (final temp – 20 deg C) • = 418 x (final temp – 20) final temp -20 = 1500/418 • Final temp = 3.59 + 20 = 23.59 deg C

More Related