Presentation on theme: "Heat naturally flows from high temperature to low temperature."— Presentation transcript:
1Heat naturally flows from high temperature to low temperature. Heat as energyHeat is energy transferred from one object to another because of a difference in temperatureHeat naturally flows from high temperature to low temperature.
2HeatJoule determined that a certain amount of mechanical work resulted from a specific amount of heat input. Joule is credited with defining Heat as energy (or transfer of energy)Heat is measure in calories or Joules.1cal = 4.186J1 cal is the amount of heat necessary to raise the temperature of 1 gram of water by 1 degree C.
3Heat14-3 Specific HeatWhen you heat an object, the temperature rise depends on mass of the object and a property of the material called “specific heat”.Q = mc(T2-T1)Q = amount of heat, m = mass, c = specific heat, T = temp.The higher the heat capacitance, the smaller the temp change for a given amount of heat input.
4Heat Calorimetry – solving problems In a closed system, the heat is transferred from the hot object to the cold object or heat lost by one object = heat gained by another.
5HeatLatent HeatWhen a material changes phases from a solid to liquid or from liquid to gas, a certain amount of energy is involved in the phase change. This is called the latent heat.Heat of Fusion: heat required to change from a solid to a liquid.Heat of Vaporization: heat required when changing from liquid to gas.Q = mL where m = mass and L = latent heat (look this up in a table)During a phase change, the material’s temperature stays constant.
6Heat Solving Calorimetry problems Apply conservation of energy Heat gained = heat lostIf no phase changes occur, each term will have the form Q(gain) = mc(Tf-Ti) or Q(lost) = mc(Ti-Tf)If phase changes occur, must account for these Q = mLWhen the system reaches equilibrium, the final temperature of each substance will have the same value.