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Thermal Energy

Thermal Energy. Heat & Temperature. Definitions. Energy Can do work Kinetic Energy Energy associated with the motion of objects, large or small Thermal Energy Kinetic energy of microscopic particles that make up all matter. Definitions. Thermal Energy

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Thermal Energy

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  1. Thermal Energy Heat & Temperature

  2. Definitions • Energy • Can do work • Kinetic Energy • Energy associated with the motion of objects, large or small • Thermal Energy • Kinetic energy of microscopic particles that make up all matter

  3. Definitions • Thermal Energy • Total amount of thermal energy an object possesses • Temperature • Average thermal energy per molecule • “Concentration” of thermal energy in an object • With the same total amount of thermal energy, a larger object has a lower temperature. • Heat • Amount of thermal energy that is transmitted from body to body. • “Thermal energy in transit”

  4. Definitions Obj A: TotalThermal Energy Obj B: Total Thermal Energy ObjA: Temperature Average Thermal Energy Obj B: Temperature Average Thermal Energy Heat ALWAYS flows from warmer to cooler!!

  5. Definitions: HEAT - continues • Amount of thermal energy that is transmitted from body to body. “Thermal energy in transit” • Thermal energy is money in the bank • Heat is the transfer of the money in and out of the bank • Flows from hotter to colder until both have the same temperature (THERMAL EQUILIBRIUM) • Body does not “have” a certain amount of heat.It “has” a certain amount of thermal energy, and then transfers heat to another body.

  6. Units: Temperature Scales • Celsius ( ̊ C ): Our unit of choice • Kelvin ( K ): Based on “absolute zero” • Molecules have NO motion (Zero kinetic / thermal energy) • Farenheit ( ̊ F ): Silly imperial unit

  7. Units: Thermal Energy & Heat • Calorie – Amount of heat needed to change the temperature of 1 gram of water 1 ̊ C. • Joule – (1 calorie = 4.18 joules) • NOT like food calories • 1 Calorie = 1000 calories • Does not measure thermal energy. Measures energy stored in chemical bonds.

  8. Temperature Scales

  9. Specific Heat Capacity • Quantity of heat required to change the temperature of a unit mass of the substance by one degree. ex: water = 1 calorie / (gram)( ̊ C) • Relationship between heat and temperature • How much heat does it take to increase the temperature

  10. Specific Heat Capacity • “Specific” – Means “per unit mass” • Capacity - Measure of a substance’s ability to “store” thermal energy. • Like a person’s “capacity” for alcoholHow much alcohol he/she can “store” before there is a change in behavior.

  11. Specific Heat Capacity:Calculations Temperature Change ( ̊ C) Thermal Energy (calories) Mass (g) Specific Heat Capacity ( calories / g * ̊ C)

  12. Specific Heat Capacity:Calculations • You want to cool down 1 liter of water. If you put 1000 g of room temperature water ( 22 ̊ C) into the refrigerator and cool it to 10 ̊ C, how much thermal energy would the water lose? • Q = ?Mass = 1000 g∆ Temp = final – initial = 10 ̊ C – 22 ̊ C = - 12 ̊ CCp = 1 calorie / g * ̊ C • Q = (1000 g) (-12 ̊ C) (1 cal / g ̊ C) = 12000 calories

  13. Laws of Thermodynamics: “The movement of heat” • When heat flows into or out of a system, the gain or loss of thermal energy equals the amount of heat transferred.(Conservation of energy) • Heat never spontaneously flows from a cold substance to a hot substance. • No system can reach absolute zero.

  14. Kinetic Molecular Theory • All matter is made up of tiny particles. • These particles are in constant motion. • Increasing the motion of the particles increases temperature. • When particles collide, they transfer energy – the higher energy particle transfers energy to the lower energy particle.BUT… there is no overall loss of energy.

  15. Thermal Expansion As a substance is heated (thermal energy is increased), particles move faster and farther apart. • Solids: • Rigid, so particles vibrate in place • Not enough energy to go anywhere • Liquids: • Enough energy to move around one another, so they flow. • Not enough energy to escape each other • Gases: • So much energy, they disperse and expand to fill whatever container they are in

  16. Thermal Transfer

  17. Thermal Transfer

  18. Kinetic Molecular Theory • All matter is made up of tiny particles. • These particles are in constant motion. • Increasing the motion of the particles increases temperature. Thermodynamics • Whenever heat flows into or out of a system, the gain or loss of thermal energy equals the amount of heat transferred. • Heat never spontaneously flows from a cold substance to a hot substance. • No system can reach absolute zero.

  19. Definitions • Kinetic energy is a general term describing the energy associated with the motion of objects (large or small objects). You can calculate the kinetic energy of an object of mass m with a velocity (speed) v from the formula K.E. = 1/2 mv^2. Thermal energy refers to the kinetic energy of the microscopic particles (atoms and molecules) that make up all samples of matter - i.e. all objects. When you add heat to an object, you increase the temperature of the object (usually) and that heat increases the kinetic energy of the molecules that comprise that object. In fact, temperature is a measure of the average kinetic energy of the microscopic particles that make up an object.

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