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Thermodynamics. Temperature. Temperature is the measurement of the average kinetic energy of material. Atoms move around and collide with the thermometer and exchange its energy causing the thermometer to go up. Three units of measuring temperature Fahrenheit (Used only in the US)
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Temperature • Temperature is the measurement of the average kinetic energy of material. • Atoms move around and collide with the thermometer and exchange its energy causing the thermometer to go up. • Three units of measuring temperature • Fahrenheit (Used only in the US) • Celsius (Used by the world) • Kelvin (Used by the scientist)
Heat • What is heat • It is the energy that is transferred due to differences in temperature. • So does a large pot of hot water by itself have heat? • How about when you put your finger in it.
Measuring Heat -Calorimetry • Joules is the unit for energy • We also use the calorie • 1 calorie is the amount of energy it takes to raise one gram of water 1° C. • Calorie = 1,000 calorie= 1 kcal • We use it for food. • 1cal = 4.186 J
Equations • Q=mcΔT: heat transfers into an object and does not change phases. • C is the specific heat. Similar to μ for friction. • Q=mhf: Heat of fusion, the heat it takes to melt something • Q=mhv: Heat of vaporization , the heat to takes to vaporize something.
Problems • How much heat must be gained to raise temperature of 0.1 kg melted ice to room temperature of 23°C?
Hypothermia Problem • Hypothermia can occur if the body temperature drops to 35 C, although people have been known to survive much lower temperatures. On January 19, 1985, 2-year-old Michael Trode was found in the snow near his Milwaukee home with a body temperature of 16.0 ° C. If Michael's mass was 10.0 Kg, how much heat did his body loose, assuming his normal body temperature was 37.0 ° C? (Chumans=3470J/kg °C
Horse Shoe problem • Read #14
Find C for lead • Preform an experiment to find leads specific heat
Question to start off the day • Design an experiment to calculate the temperature of red hot brass sphere with the use of snow/ice? • Brass’s specific heat is 377 J/Kg C • Supplies available: • Thermometers • Red Hot brass sphere • Beaker of snow/Ice • Empty beaker • Scale
Heat Transfer • Spontaneous transfer of heat is always from the warmer object to cooler object. • There are three ways that heat can transfer • Conduction • Convection • Radiation
Conduction • (Thermo) Conductor: Materials that conduct heat well. • Name some materials that are good conductors? • Conduction happens when the atoms or molecules collided with each other and exchange their energy. • Ex: In an iron rod the flame cause the atoms at the heated end to vibrate more rapidly. These atoms vibrate against there neighboring atoms, which in turn do the same thing. • Insulators are poor conductors of heat.
Convection • Convection is when heat transfers by moving the atoms or molecules move away from the heat source and the cooler atoms or molecules move to the heat source. Winds are caused by convection Why is San Fransisco warmer then D.C when they are at the same latitude?
Radiation • Radiation in the process of transmitting energy thru space via radiant energy. • Radiant Energy is a form of electromagnetic waves (AKA light) • Do NOT get it confused with Nuclear radiation!! • Absorption and reflection of radiant energy is like mirrors and windows for radiant energy. Good absorber will absorb heat and Poor absorbers reflect radiate energy. • What could that be used for?
Problem • Name situations where we see: • Conduction • Convection • Radiation
Questions • Why does a piece of room temperature metal feel cooler to the touch than paper, wood or cloth? • Why does the direction of coastal winds change from day to night? • When a space shuttle is in orbit and there appears to be no gravity in the cabin, why can a candle stay lit?
Frist Law of Thermodynamics First law of thermodynamics by Rudolf Clausius in 1850. • In a thermodynamic process of a closed system, the increment in the internal energy is equal to the difference between the increment of heat accumulated by the system and the increment of work done by it. • Another words Etotal=Q-W • Total Energy = (Heat added to the system) – (The work done by the system)
Side note • It is typical for chemistry texts to write the first law as ΔU=Q+W. It is the same law, of course - the thermodynamic expression of the conservation of energy principle. It is just that W is defined as the work done on the system instead of work done by the system. In the context of physics, the common scenario is one of adding heat to a volume of gas and using the expansion of that gas to do work, as in the pushing down of a piston in an internal combustion engine. In the context of chemical reactions and process, it may be more common to deal with situations where work is done on the system rather than by it.
Second Law of Thermodynamics • Second Law of thermodynamics by Rudolf Clausiusin 1850 • "It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects.” • Another words you can not get 100% efficiency out of a system.
Third law of thermodynamics • Third law of thermodynamics by Walther Nernst in 1912 • The entropy of a perfect crystal at absolute zero is exactly equal to zero. • Another word it is impossible to reach absolute zero. Lowest temps Utah: -56 ° C at Peter’s Sink; February 8, 1985 USA: -62 ° C at Prospect Creek Camp, Alaska; January 23, 1971 Earth: -89.2° C at Antarctica 1983 Universe: -270.6° C (2 K) found by COBE satellite; 1990 Ever recorded: 500 picokelvin (-273.14999999995°C) at MIT; 2003
Laws of an argument &Thermodynamics • The laws of an argument with a women • You can’t win, you can only tie. • You can only tie when you’re absolutely right. • You can’t tie • The laws of Thermodynamics • You can’t win, you can only break even. • You can only break even at T=0 • You can’t reach T=0
