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Chapter 7 Gases

Chapter 7 Gases. 7.1 Properties of Gases 7.2 Gas Pressure. Kinetic Theory of Gases. A gas consists of small particles that move rapidly in straight lines have essentially no attractive (or repulsive) forces are very far apart

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Chapter 7 Gases

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  1. Chapter 7 Gases 7.1 Properties of Gases 7.2 Gas Pressure

  2. Kinetic Theory of Gases A gas consists of small particles that • move rapidly in straight lines • have essentially no attractive (or repulsive) forces • are very far apart • have very small volumes compared to the volumes of the containers they occupy • have kinetic energies that increase with an increase in temperature • are in constant motion.

  3. Properties of Gases • Gases are described in terms of four properties: pressure (P), volume (V), temperature (T), and amount (n).

  4. Gas Pressure Gas pressure • is the force acting on a specific area Pressure (P) = force area • has units of atm, mmHg, torr, lb/in.2 and kilopascals(kPa). 1 atm = 760 mmHg (exact) 1 atm = 760 torr 1 atm = 14.7 lb/in.2 1 atm = 101.325 kPa

  5. Learning Check A. What is 475 mmHg expressed in atmospheres (atm)? 1) 475 atm 2) 0.625 atm 3) 3.61 x 105 atm B. The pressure in a tire is 2.00 atm. What is this pressure in mmHg? 1) 2.00 mmHg 2) 1520 mmHg 3) 22 300 mmHg

  6. Solution A. What is 475 mmHg expressed in atm? 2) 0.625 atm 475 mmHg x 1 atm = 0.625 atm 760 mmHg B. The pressure of a tire is measured as 2.00 atm. What is this pressure in mmHg? 2) 1520 mmHg 2.00 atm x 760 mmHg = 1520 mmHg 1 atm

  7. Atmospheric Pressure Atmospheric pressure • is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth

  8. Atmospheric Pressure (continued) Atmospheric pressure • is about 1 atmosphere at sea level • depends on the altitude and the weather • is lower at high altitudes where the density of air is less • is lower on a rainy day than on a sunny day

  9. Barometer A barometer • measures the pressure exerted by the gases in the atmosphere • indicates atmospheric pressure as the height in mm of the mercury column

  10. Learning Check A. The downward pressure of the Hg in a barometer is _____ the pressure of the atmosphere. 1) greater than 2) less than 3) the same as B. A water barometer is 13.6 times taller than a mercury barometer (DHg = 13.6 g/mL) because 1) H2O is less dense 2) H2O is heavier 3) air is more dense than H2O

  11. Solution A. The downward pressure of the Hg in a barometer is 3) the same as the pressure of the atmosphere. B. A water barometer is 13.6 times taller than a mercury barometer (DHg = 13.6 g/mL) because 1) H2O is less dense

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