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Charles Law: The Relationship between the Volume and Temperature

Charles Law: The Relationship between the Volume and Temperature. Lesson 3. Celsius and Kelvin Temperature. In SI Metric the temperature scale is defined as Kelvin temperature scale . The degree unit is the Kelvin (K). The symbol for the unit is K, not o K. 

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Charles Law: The Relationship between the Volume and Temperature

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  1. Charles Law: The Relationship between the Volume and Temperature Lesson 3

  2. Celsius and Kelvin Temperature • In SI Metric the temperature scale is defined asKelvin temperature scale. • The degree unit is the Kelvin (K). The symbol for the unit is K, not o K.  • Kelvin temperatures must be used in many gas law equations in which temperature enters directly into the calculations. 

  3. Celsius and Kelvin Temperature • The Celsius and Kelvin scale are related unit for unit. One degree unit on the Celsius scale is equivalent to one degree unit on the Kelvin scale. The only difference between these two scales is the zero point.  • The zero point on the Celsius scale was defined as the freezing point of water, which means that there are higher and lower temperatures around it. 

  4. Celsius and Kelvin Temperature • The zero point on the Kelvin scale - calledabsolute zero– it corresponds to the lowest temperature that is possible.  It is 273.15 units lower than the zero point on the Celsius scale.

  5. Celsius and Kelvin Temperature • So this means that 0 K equals -273.15 oC and 0oC equals 273.15 K. Thermometers are never marked in the Kelvin scale. • If we need degrees in Kelvin the following relationships are to be used.  TK=  tc  +  273.15  or      tc  =  TK  -  273.15

  6. Example • Cold Saunas are available a high end resorts. Instead of heating the sauna and causing the people inside to sweat, a cold sauna is cooled down to -110 ° C. What would the temperature be in Kelvin? • TK=  tc  +  273.15  • TK=  -110  +  273.15  • TK=  163.15 K

  7. Questions • Liquid nitrogen (sometimes abbreviated LOX) is used in liquid-fuel rockets. Its boiling point is -183oC. What is this temperature in Kelvin’s?  • A substance is heated from 300 K to 315 K. What is the change in temperature expressed in °C.

  8. Questions • Perform the following conversions

  9. Questions • A clinical thermometer registers a patient's temperature to be 37.13oC. What is this in Kelvin’s? • The coldest permanently inhabited place on earth is the Siberian village of Oymyakon in Russia. In 1964 the temperature reached a shivering -71.11oC. What is this temperature in Kelvin’s?

  10. Helium has the lowest boiling point of any liquid. It boils at 4 K. What is this in oC?

  11. Charles Law

  12. Charles Law • The direct relationship between the volume of a gas and the temperature of the gas (on the Kelvin temperature scale) is known as Charles Law. According to this law, • as the temperature of a gas increases, the volume increases proportionally, provided that the pressure and the amount of gas remains the same.

  13. Charles's Law • However, as the graph above shows, the volume extrapolates to zero at a temperature of -273.15oC. If this temperature were taken as the zero of a temperature scale then all negative temperatures could be eliminated. 

  14. Charles's Law • Such a temperature scale is now the fundamental scale of temperature in the SI. It is called the absolute scale, the thermodynamic scale, and the Kelvin scale. Temperature on the Kelvin scale, and only on the Kelvin scale, is symbolized by T. 

  15. Charles’s Law Charles’s Law can be written as V1T2= V2T1

  16. Example: 1 • The volume of a sample of gas is 23.2 cm3 at 20oC. If the gas is ideal and the pressure remains unchanged what is its volume at 80oC?

  17. Example 1

  18. Example: 2 • Compressed oxygen is widely used in hospitals and retirement homes. To make it easier to transport, the oxygen is cooled. How many degrees Celsius would the gas be if 200 L’s at 23 degrees Celsius is compressed to 40 L?

  19. Example: 2

  20. Questions: • page 432 # 13-14 • page 434 # 16-19. • Temperature and pressure law next

  21. Pressure and Temperature Law • When a gas is heated the pressure also increases, if we assume the volume and the amount of gas remains the same, the quotient of the two variables (p/T) has a constant value (k). • Because it remains the same it allows us to compare different sets of temperatures and pressures.

  22. This is known as the pressure and temperature law or the Gay-Lussac’s Law.

  23. Example • An aerosol can of paint contains a pressure of 138 kPa at 20 °C. The can is left in a parked car and is heated to 50 ° C. What it the final pressure in the can?

  24. Questions: • page 432 # 13-14 • page 434 # 16-19. • Page 435 # 22-25

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