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It is hot!

HEAT. It is hot!. Defining Heat. The energy transferred between objects of a difference in their temperature Always Hot to Cold! Measured in Joules or calories 1 calorie = 4.186 J Transfer can alter temperature or phase Can be due to energy change. Conservation of Energy.

blake-holloway
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It is hot!

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  1. HEAT It is hot!

  2. Defining Heat • The energy transferred between objects of a difference in their temperature • Always Hot to Cold! • Measured in Joules or calories • 1 calorie = 4.186 J • Transfer can alter temperature or phase • Can be due to energy change

  3. Conservation of Energy • When work is done or energy changes, energy transfer is called Heat. • Heat can be increase in Internal Energy • IE is the total KE of all the particles in that object. How hot it is. Like temperature. • Example: Push Bob with force of 400N, 35m across floor. Bob heats up, IE goes up 20%. Figure initial IE in Bob. • Answer should be 70000 J. Boo-yaa.

  4. Another one: Mr. Hammer says to Mr. Nail: “Ima gonna hamma you!” Mr. Hammer has a mass of 0.25 kg and hammers with a speed of 3 ms-1. Mr. Nail absorbs 85% of Mr. Hammer’s Kinetic Energy. Figure out rise in IE of Mr. Nail. • Answer is a whopping 0.96 J. Bungers.

  5. Specific Heat Capacity • Quantity of energy needed to raise the temperature of 1 kg of a substance 1o Celsius at constant pressure. • Q = mcpΔT • Q= heat, m=mass, cp=specific heat capacity, ΔT=change in temp in oC. • Keep in mind: use this only during TEMPERATURE CHANGES!

  6. Example this! • I heat my 25.5 g gold wedding ring to a temp of 50oC and place it in a cup with 0.05 kg of water at 24oC. Uh-oh,. What is the final temp? • Hint: Use Table 10-4 on page 372. • Answer: 24.40C

  7. Latent Heat • Defined as heat required to change the phase of a substance. • 2 kinds: fusion or vaporization • During phase changes, there is NO TEMPERATURE CHANGE!!!! Bunyan! • Q=mL (think: Quiet Mr. Lemke) • Use this only during phase change, not during temperature change. • Use table 10-6 on page 379.

  8. Examplify! • How much energy is removed when 10.0 g of water is cooled from steam at 133.0o C to liquid at 53.0o C? • Hint: Draw diagram. You should then see this is a three part problem: Two temperature changes and one phase change. • Add up all energies for the answer. • Answer: 25200 J!

  9. Heat Transfer: 3 types • Conduction: by direct contact. TOUCH! • Convection: by displacement of cold matter with hot matter. i.e.: Air or liquid movements. WIND! • Radiation: by electromagnetic waves. LIGHT!....(Infrared!)

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