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Chemistry Notes

Chemistry Notes. Measuring Changes in Enregy. Matter and Energy. Terms: System – the small part of the universe under consideration. Matter and Energy. Question: How does matter energy relate? Answer : Matter can have energy (potential or kinetic) or it can be converted to energy.

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Chemistry Notes

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  1. Chemistry Notes Measuring Changes in Enregy

  2. Matter and Energy Terms: • System – the small part of the universe under consideration.

  3. Matter and Energy • Question: How does matter energy relate? • Answer: Matter can have energy (potential or kinetic) or it can be converted to energy.

  4. Matter and Energy Matter transfers energy in different ways Changes in Energy can be measured

  5. Matter and Energy Energy – the capacity to do work • Units for energy – joules (J) or calories (c) • Thermal energy – the sum of all the kinetic energy of particles in matter. • Heat – the transfer of thermal energy • Heat moves from hot to cold places • Symbol for heat of T.E. is “Q”

  6. Matter and Energy Energy and Chemical Change • Chemical changes are always accompanied by a change in energy. • Two Types • Endothermic • Exothermic

  7. Matter and Energy • Endothermic reaction – energy is absorbed in a reaction • Ex: photosynthesis

  8. Matter and Energy • Exothermic reaction – energy is given off by a reaction • Hot packs • Fire

  9. Matter and Energy • Activation energy – the minimum amount of energy needed for a reaction to occur.

  10. Measuring Energy Changes in Matter • Calorimeter – device used to measure the energy given off or absorbed during a chemical reaction.

  11. Measuring Energy Changes in Matter • Specific Heat – the heat needed to raise one gram of a substance one degree Celsius • Specific heat of water – 4.184 J/g*oC • c = specific heat

  12. Measuring Energy Changes in Matter • To calculate energy lost or gained from a reaction  Q = mcΔT • Ex: how much heat is lost when solid aluminum with a mass of 4110 g cools from 660.0oC to 25oc? (Specific Heat = 0.903 J/g*C) Q = mcΔT Q = (4110 g) (0.903 J/g*C) (660°-25°) Q = 2,360,000 J

  13. Measuring Energy Changes in Matter

  14. Measuring Energy Changes in Matter

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