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Heat Energy

Heat Energy. Increasing the temperature of 1 kg of water from 10 o C to 15 o C takes _________ energy compared to the energy needed to increase its temperature from 15 o C to 20 o C. A. more B. less C. the same

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Heat Energy

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  1. Heat Energy Increasing the temperature of 1 kg of water from 10oC to 15oC takes _________ energy compared to the energy needed to increase its temperature from 15oC to 20oC. A. more B. less C. the same Increasing the temperature of 1 kg of water from 10oC to 15oC takes _________ energy compared to the energy needed to increase the temperature of 2 kg of water by the same amount. A. more B. less C. the same

  2. Heat Energy Increasing the temperature of 1 kg of water from 10oC to 15oC takes _________ energy compared to the energy needed to increase its temperature from 15oC to 20oC. A. more B. less *C. the same Increasing the temperature of 1 kg of water from 10oC to 15oC takes _________ energy compared to the energy needed to increase the temperature of 2 kg of water by the same amount. A. more *B. less C. the same

  3. Latent Heat 3U Physics

  4. A Caveat Note that the equation Q = mcDT can only be applied if the material does not change state while changing temperature.

  5. The Heating Curve Changes of state require additional energy:

  6. Latent Heat of Fusion Additional heat is required to change a material’s state from solid to liquid (at the melting point): Q = mLf where Lf is the latent heat of fusion (different for different materials).

  7. Latent Heat of Fusion This heat is absorbed by the material when it melts and released when it freezes.

  8. Latent Heat of Fusion Latent heat explains why ice stays on the ground even when the temperature is above 0oC – it takes additional latent heat to do the melting.

  9. Latent Heat of Vapourization Similarly, additional heat is to change a material’s state from liquid to gas (at the boiling point): Q = mLv where Lv is the latent heat of vapourization (different for different materials).

  10. Latent Heat of Vapourization This heat is absorbed by the material when it ____________ and released when it ____________.

  11. Latent Heat of Vapourization This heat is absorbed by the material when it evaporates and released when it condenses.

  12. Latent Heat of Vapourization Latent heat explains why sweating cools you down – the sweat absorbs heat energy from your skin when it evaporates.

  13. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? Note cwater = 4200 J/kgoC cice = 2100 J/kgoC Lf(water) = 3.3 x 105 J/kg

  14. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? To cool the water to 0oC: Q = mcDT = (0.10 kg)(4200 J/kgoC)(80.0oC) = 33 600 J

  15. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? To cool the water to 0oC: Q = mcDT

  16. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? To freeze the water at 0oC: Q = mLf

  17. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? To freeze the water at 0oC: Q = mLf = (0.10 kg)(3.3 x 105 J/kg) = 33 000 J

  18. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? To cool the ice to -30.0oC: Q = mcDT

  19. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? To cool the ice to -30.0oC: Q = mcDT = (0.10 kg)(2100 J/kgoC)(30.0oC) = 6 300 J

  20. Latent Heat: Example How much heat must be removed from 0.10 kg of water at 80.0oC to cool it to ice at -30.0oC? 33 600 J + 33 000 J + 6 300 J = 7.3 x 104 J

  21. More Practice Homework Set 9: Latent Heat

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