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Energy and Temperature

Energy and Temperature. Energy. Energy – The ability to cause change or do work There are many kinds of energy: Electrical – PE Mechanical – KE Chemical – PE Heat, thermal – KE Nuclear Sound Light

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Energy and Temperature

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  1. Energy and Temperature

  2. Energy • Energy – The ability to cause change or do work • There are many kinds of energy: • Electrical – PE • Mechanical – KE • Chemical – PE • Heat, thermal – KE • Nuclear • Sound • Light • Chemistry deals mainly with the conversion of chemical into heat, light, and electrical

  3. Types of Energy • Energy can be defined as one of three types • Radiant energy - sunlight • Kinetic Energy (KE) Energy of an object in motion • KE = ½ mv2 • Potential Energy (PE) Stored energy due to position or composition – Gravitational Potential Energy • PE – mgh or fd

  4. Measuring Energy • calorie (cal) • Common unit of energy • Amount of heat needed to raise the temperature of 1 gram of water by 1 °C • Joule (J) • SI unit of energy • 1 cal = 4.184 J

  5. Energy stored in food • Calorie (Cal) • 1000 calories or 1 kilocalorie

  6. Example 1 • A student uses 30 J of energy putting books on a shelf in the classroom. Convert this amount of energy from joules to calories.

  7. Example 2 • Suppose you use 135 cal of energy to perform a task. How many joules have you used?

  8. Example 3 • The energy content of a small tomato is about 17 Cal. Convert this measurement to joules.

  9. Law of Conservation of Mass • Matter cannot be created or destroyed in ordinary chemical or physical changes • Energy is transformed to another kind or transferred to another object • Nuclear reactions are the exception to the rule

  10. Energy Crisis • “running out of energy” • Society depends on chemical energy in form of fossil fuels • Coal and petroleum

  11. Temperature • A measurement of the average kinetic energy of the particles in a sample • To record temperatures and changes accurately a scale has to be defined and used • Measurements taken with thermometers

  12. Kelvin Scale • The Kelvin temperature scale is the official SI scale but Celsius is more commonly used, except when dealing with gases • Absolute zero – (-273°C) the point at which motion of particles matter ceases

  13. Comparing Temperature Scales

  14. Converting Temperature • Celsius to Kelvin • Add 273 • K = °C + 273 • Kelvin to Celsius • Subtract 273 • °C = K - 273

  15. Example 1 • Temperatures close to absolute zero are incredibly cold – at 50 K air will freeze into a solid! Convert 50 K to the Celsius scale

  16. Example 2 • Normal body temperature is 310 K. Convert 310 K to the Celsius scale.

  17. Example 3 • Antifreeze, or ethylene glycol, boils at 199°C. Convert 199°C to the Kelvin scale.

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