Phases and Phase Changes

Question 1

Vapor Pressure

Answer 1

• Vapor pressure is the force per unit area above the surface of a liquid exerted by molecules formed upon evaporation of the liquid
  
  • If a liquid has a high vapor pressure, there are many evaporated molecules above the liquid’s surface; this is due to a lower boiling point

Question 2

Vapor Pressure and Temperature

Vapor Pressure and Heat of Vaporization

Vapor Pressure and Boiling Point

Answer 2

• Vapor pressure increases when temperature increases
• Vapor pressure decreases with increasing heat of vaporization
• Vapor pressure decreases with increasing boiling point

Question 3

Boiling Point

Answer 3

• The boiling point is the temperature at which the vapor pressure of a liquid is equal to the atmospheric pressure
  
  • Therefore, at decreased atmospheric pressure, a liquid’s boiling point is reached at a both a lower temperature and lower vapor pressure
• Boiling point also decreases when impurities are added (think salt for pasta)