Unit 103 power_point_1_temperature

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Unit 103 power_point_1_temperature

  1. 1. Temperature
  2. 2. DEFINITIONTemperature is the degrees of “HOTNESS” or“COLDNESS” of a body.If something measuring temperature reads 100°C, this does not say howmuch heat is present, only its level of HOTNESS.10 litres of water at 100°C would contain more heat than 1 litre of water at100°C.ScalesFahrenheit Not used as much nowCelsiusKelvinSometimes called centigrade, usually written as “C”0K = Absolute ZeroAt 0K a gas would be reduced to nothing.
  3. 3. Temperature measuring toolsTo produce a temperature scale, a minimum of two fixed points is required.The two fixed points on the Celsius scale of temperature are:• melting point of ice• boiling point of water.A tool which is used to measure low temperatures is called a thermometer.Most substances expand when heated and contract when cooling.One of the most common ways of measuring temperature is to use this fact.
  4. 4. Glass thermometer100°C0°CSealed tubecontainingmercury or alcoholMercury and alcohol are used inthermometers. They expandwith a rise in temperature.They contract with a fallin temperatureThe range between the freezing andboiling temperature is large. Mercuryfreezes at -39°C and boils at 375°C.Alcohol freezes at –112°C and boils at78°C. Mercury thermometers are usedto measure high temperatures.
  5. 5. The SI unit of temperature is the A temperature of one Kelvin isexactly equal to one degree Celsius. The diagram shows the relationshipbetween the temperature scales.“KELVIN”.The scales are different butthe temperature intervals(each single degree) are thesame.KelvinCelsius/Centigrade Fahrenheit273K Freeze Pointof water0K0°C 32°F-273°C100°C 212°F373K180Divisions100Divisions
  6. 6. Temperature conversionchartThe point -40°C and -40Fmeet. This gives a quickway of converting.021232100-40Degree CDegree F
  7. 7. These are the scales at atmospheric pressure (1013mb)TEMPERATURE SCALESCelsiusCentigradeFahrenheitFreezing PointBoiling Point0K = -273°C absolute zero273K = -0°C the ice point of water (change of state)373K = 100°C the steam (gas) point (change of state)0 32212100
  8. 8. Changing scalesBoth scales are still widely used and conversion from one to the other issometimes necessary. To convert:Centigrade to Fahrenheit = °C x 9/5 + 32Fahrenheit to Centigrade = (°F - 32) x 5/9An “rough” method of conversion:Centigrade to Fahrenheit =Fahrenheit to Centigrade =°C x 2 + 30°F - 302
  9. 9. By using your conversion formulas, complete the following table.°F °CFreezing point of water 32Boiling point of water 100Hot water storage temperature 60Normal room temperature 70Normal showering temperature 40Melting point of lead 327021214021104620
  10. 10. Temperature can be measured using a number of tools. NameTWO.1)2)Name TWO tools used to control thetemperature of water in a central heating system.1)2)THERMOMETERTHERMOCOUPLECYLINDER THERMOSTATBOILER THERMOSTAT
  11. 11. Convert these temperatures: -60°C to F 8°C to F 2°C to F 120°F to C 15°F to C
  12. 12. ANSWERS -60°C to F = 76°F 8°C to F = 46.4°F 2°C to F = 35.6°F 120°F to C = 48.8 °C 15°F to C = -9.4 °C

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