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Exploring Temperature, Heat, and Expansion in Physics

This educational content delves into the concepts of temperature, heat transfer, internal energy, and specific heat in physics. Learn about thermal expansion, specific heat formulas, and practical examples. Explore the relationship between heat, temperature change, and energy transfer.

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Exploring Temperature, Heat, and Expansion in Physics

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  1. 15 Temperature, Heat, Expansion • Temperature & Heat • Internal Energy & Specific Heat • Homework: • RQ: 1, 2, 7, 8, 10, 12, 15, 21, 24.

  2. Temperature • T ~ • Ex: hammered metal • Expansion with T increase

  3. Superheating • Mythbusters • Instant coffee

  4. Water Expansion • Water expands from 4°Cto 100°C (as does most materials) • However, water contracts when warmed from 0°C to 4°C. (transient ice melting)

  5. Heat • ‘heat’ is a transfer of thermal energy due to temperature difference • Examples: • ice in warm liquid: heat flows from liquid to the ice • warm liquid is put in a refrigerator: heat flows from drink to the cold air in refrigerator • //

  6. Internal Energy • the total of all molecular energies, kinetic plus potential, that are internal to a substance. It is ~ (mass) x (temperature). • Heat ≠ Internal Energy, • however, for a thermal-only process, • Heat = D(Internal Energy)

  7. mixing: ‘hot’ and ‘cold’ = ‘warm’ • for liquids & solids: heat ~ (mass)x(temperature change) • when ‘hot’ and ‘cold’ are mixed, heat lost by ‘hot’ = heat gained by ‘cold’ • Ex. 1kg water at 0°C is mixed with 1kg water at 20°C: • (1kg)(T - 0) = (1kg)(20 – T)

  8. Calories and Joules • 1 Calorie = _______ calories • 1 calorie = ________ joule • Calorie is the common food unit. • Btu’s are also used, e.g. gas range

  9. Specific Heat • quantity of heat required to raise the temperature of 1kg by 1°C. //

  10. specific heat • c = Q/(mDT) [J/(kg·K)] • c = heat/(massx temperature change) • Water: 4186 J/kgC • heat needed per kg to raise temperature by 1 degree C or K.

  11. summary • T ~ KE/molecule • most substances undergo thermal expansion (note the water exception) • heat is an exchange of thermal energy • superheating • specific heat = heat needed to raise temp. of 1kg by 1C (substance dependent)

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