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Chemistry 4d & 4e: STP & C:K

This chemistry lesson covers standard temperature and pressure (STP) and the conversion between the Celsius and Kelvin temperature scales. It explains the values and meanings of STP, why it is important, and how to convert between Celsius and Kelvin temperatures. Examples and practice problems are provided.

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Chemistry 4d & 4e: STP & C:K

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  1. Chemistry 4d & 4e: STP & C:K

  2. Chemistry 4D. Students know the values and meanings of standard temperature and pressure (STP).

  3. Standard Temperature and Pressure (STP) • Standards are an agreed-upon set of conditions for gases against which to consider other temperatures and pressures. • Standard temperature is zero degrees Celsius (0 ۫C) • Standard pressure is one atmosphere (760mm Hg).

  4. Why do we need STP? • When volumes of gases are being compared, the temperature and pressure must be specified. • For a fixed mass of a gas at a specified temperature and pressure, the volume is also fixed.

  5. Chemistry 4E. Students know how to convert between the Celsius and Kelvin temperature scales.

  6. The Kelvin Scale • Some chemical calculations require an absolute temperature scale

  7. The Kelvin Range • The coldest possible temperature is equal to zero. • There are no negative temperatures on the Kelvin scale.

  8. Absolute zero = 0 K • In theory if a sample of any material is cooled as much as possible, the lowest temperature that can be reached is 0 K • 0 K has been experimentally determined as equivalent to –273.15۫C. • The Kelvin scale starts with absolute zero (0 K) because of this theoretical lowest temperature limit.

  9. K:C Conversion • A Kelvin temperature is always 273.15 degrees greater than an equivalent Celsius temperature. • The magnitude of one unit of change in the K scale is equal to the magnitude of one unit of change on the C scale. • A Kelvin temperature is specified without the degree symbol.

  10. K:C Conversion • When going from ۫C to K  add 273 • When going from K to ۫C  subtract 273 • Δ1 K = Δ1 ۫C • Kelvin has no degree symbol.

  11. K:C Conversion—Examples When going from ۫C to K  add 273 Water freezing 0 ۫C 0 ۫C + 273 = 0 ۫C + 273 = 273 K 0 ۫C = 273 K

  12. K:C Conversion—Examples When going from K to ۫C  subtract 273 Absolute zero 0 K 0 K - 273 ۫C = 0 K - 273 ۫C = -273 ۫C 0 K = -273 ۫C

  13. C:F Conversion—Examples When going from ۫F to ۫C ۫ C = 5/9 * ( ۫F – 32) Ex. If it’s 85 ۫F in Los Angeles today, how hot is that in ۫C ? ۫ C = 5/9 (85 ۫F – 32) ۫ C = 5/9 (53 ۫F) ۫ C = 29.4 ۫F

  14. C:F Conversion—Examples When going from ۫C to ۫F ۫۫F = (9/5)* ۫C + 32 Ex. If it’s 34 ۫C in Mexico City today, how hot is that in ۫F ? ۫۫F = (9/5)*(34 ۫C) + 32 ۫۫F = 61 ۫C + 32 ۫۫F = 93 ۫C

  15. K:C Conversion—Your Turn When going from ۫C to K  add 273 Body Temperature 37 ۫C. How much is this in K? 37 ۫C 37 ۫C + 273 = 37 ۫C + 273 = 310 K 37 ۫C = 310 K

  16. Complete the table

  17. Complete the table--Solution

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