[PHY] Chapter 10 - Temperature

DARRELL ER (COPYRIGHTED) © TOPIC 10: TEMPERATURE DARRELL ER (COPYRIGHTED) ©

CHAPTER ANALYSIS THE ABOUT MASTERY EXAM WEIGHTAGE DARRELL ER (COPYRIGHTED) ©

TEMPERATURE & THERMAL ENERGY THERMOMETRY & CALIBRATION THERMOMETRIC PROPERTIES KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

TEMPERATURE Temperature is a measure of the degree of hotness of a body. It is also a measure of the average kinetic energy of molecules in a body. THERMAL ENERGY Thermal energy is the measure of the total kinetic energy of all molecules in a body. KELVIN & DEGREE CELSIUS 273 Kelvin = 0 Degree Celsius 373 K = 100 °C 0 K = - 273 °C TEMPERATURE & THERMAL ENERGY DARRELL ER (COPYRIGHTED) © The hot coffee has a higher temperature, but not more internal energy. Although the iceberg is at a lower temperature, it’s enormously greater mass means that its total kinetic energy is still much greater than that of the coffee.

CALIBRATION OF THERMOMETERS Makes use of a physical property that varies with temperature, known as the thermometric property. Steps to construct a thermometer: 1) Select a thermometric property that changes continuously and linearly with temperature 2) Select 2 fixed points (usually ice point & steam point) 3) Select appropriate divisions PRINCIPLE OF THERMOMETRY DARRELL ER (COPYRIGHTED) © PRINCIPLE OF THERMOMETRY Thermal properties are physical properties that vary with temperature. A good thermometric property should: 1) Sensitive to temperature changes (ability to reflect small change) 2) Respond quickly to temperature changes (time taken to respond to change) 3) Vary at a constant and unique rate accordingly to temperature (for calibration) 4) Accommodate wide range of temperature (usability)

THERMOMETRIC PROPERTIES DARRELL ER (COPYRIGHTED) © Thermometric Property Thermometer Volume of fixed mass of liquid Mercury-in-glass thermometer Alcohol-in-glass thermometer Resistance of wire Resistance thermometer Electromotive force Thermocouple Liquid-in-glass thermometer As temperature increases, liquid expands and the thread of liquid in the capillary tube increases in length. (Limited range of temperature that it can measure) Resistance thermometer Usually made of platinum due to its linear resistance-temperature relationship and chemical inertness. (Accurate & can measure wide range of temperature) Thermocouple Consists of 2 wires of different metals joined together at the ends to form 2 junctions. (Hot & cold) (Can measure temperature at a point, quick response)

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