midterm 1

• Gases move essentially freely. They are compressible and exert a pressure on the container. The have no distinct shape and no defined volume. 
• Which is correct rank of liquids, solids, and gases in terms of their density; in general. 

  gases < liquids < solids 
• In an ideal gas, molecules move randomly . They do not interact with other gas molecules and all collisions are elastic . The individual gas molecules have zero volume.
• Low pressure and high temperature are the conditions for gases to move ideally
• What is Boyle's Law relationship between volume and pressure?

  They are inversely proportional P = 1/V
• What is Avogadro's Law for volume and moles?

  V is proportional to n
• What is the relationship between pressure and temperature?

  Pressure is proportional to T
• The units for R is atmL/molK
• Units

  • Molar mass: grams/mols
  • Density: gram/mL
  • Molar Density: mols/L
• Total pressure of a system is equal to the sum of the partial pressures 
• The partial pressure is proportional to the mole fraction 
• Molecules are points, that is they have finite mass but no volume .

  There is constant, random motion and collisions are elastic .

  Gas molecules are Neither attracted or repulsed by other molecules . 

  The average energy is directly proportional to temperature
• Most gases can be treated as ideal at high temperature and low pressure. Gases also behave most ideally when there are large spaces between molecules and the gas molecules take up a small percentage of the total volume. 
• Which conditions are most likely to INCREASE the attractive force between gas molecules?

  • low temperatures
  • high masses
  • high intermolecular forces
• What is the Van Der Wals equation?

  P + a(n/v)^2 * [V - nb] = nRT
• Thermodynamics is the study of energy and its interconverstion
• Energy is the capacity to do work
• work is the way of exchanging energy corresponding to a forcer exerted over a distance
• Kinetic energy is energy of motion
• Thermal energy is the energy associated with temperature
• Potential energy is energy that is stored in an object associated with composition and position
• State functions are pathway Independent . For example, imagine you climb a hill, the change in elevation is a State Function , but the number of steps you take to reach the top is a Path Function . 
• What is internal energy?

  • the sum of potential and kinetic energy
  • state function
• If I put energy into the system then the sign on the energy is positive . In this case the change for the surrounding's energy would be negative .
• If a system does work, then we say the sign on it's work is negative .
• While holding a cup of coffee, my hands start to warm up. This is an example of energy transferring in the form of heat , which is positive when we consider my hands to be the system.
• The first law of thermodynamics states that the total energy of the Universe is constant. 
• Heat is the transfer of thermal energy
• Thermal equilibrium is the state of being when the system and the surroundings have reached the same temperature
• Heat capacity is the amount of heat a system must absorb to undergo a specified change in temperature
• specific heat capacity is the amount of heat required to raise 1 gram of a substance at 1 C
• Molar heat capacity is the amount of heat required to raise 1 mole of a substance at 1 C
• What are the two equations to calculate work?

  • w = -Pressure * change in volume
  • w = Force * Distance
• What is the sign for work in each situation?

  • a balloon expands: negative
  • Gas in a rigid container (constant volume) is warmed: zero
  • A weight is place on top of a cylinder causing the volume to decrease: positive
• If the volume of a bomb calorimeter is always constant, what is the work?

  zero
• What is the units for heat capacity of a calorimeter?


  J/C
• Enthalpy is a measure of what?

  energy
• Enthalpy is a state function. It's equal to heat at a constant pressure
• elements that can no longer be anything has an enthalpy of what?


  0
• All calorimetry is used to measure heat. When work is small heat, enthalpy, and internal energy are approximately equal