Temperature and Ideal Gases Flashcards
Define 1 mole
The amount of a substance which contains the same number of particles as 12g of carbon-12.
Avogadro’s constant (NA) =
The number of particles in one mole of a substance
NA = Total number of particles / number of moles
NA = N/n
State Boyle’s law
The pressure exerted by a fixed mass is inversely proportional to volume, provided that temperature is constant (p = k/V)
State Charles’s law
Volume of an ideal gas is directly proportional to temperature.
Therefore pV/T = k
Define an ideal gas
Any gas for which pV/T remains constant at a fixed mass.
State the equation of state
pV = nRT
State the assumptions of the kinetic theory of gases
- Forces between particles are negligible, except during collisions.
- The volume of the particles is negligible compared to the volume of space occupied by the gas.
- The particles move in a straight line at a constant velocity for the majority of the time (the times of collisions are negligible compared to the times between collisions)
- Collisions are perfectly elastic (no kinetic energy is lost)
According to the kinetic model, pressure (p) =
P = mc^2/3l^3 PV = (1/3)(Nm) = nRT
Define thermal equilibrium
When 2 objects are at the same temperature, and so there is no net transfer of thermal energy between them.
Describe the Kelvin scale
T(K) = T(C) + 273
2 fixed points :
1. Absolute zero (temp. at which substances have the minimal possible amount of internal energy).
2. The triple point of water (273K; where ice, water and water-vapour can coexist)
State and explain the change in temperature during a change of state
Temperature stays the same
Kinetic energy is constant
Input energy is used to break bonds
Molecules separate, so electrical potential energy increases
Describe the process of evaporation
When there is a change from liquid to gas, without boiling
Particles with the most energy escape from the surface of the liquid
So only particles with below-average temperature remain (temperature is a measure of average kinetic energy)
Therefore there is a net outflow of energetic molecules, and so temperature decreases.
Define internal energy
The sum of the random distribution of kinetic and potential energies of a system’s atoms or molecules.
State the first law of thermodynamics
Increase in internal energy = energy supplied by heating + energy supplied by doing work.
(🔺U = q + w)
Define specific heat capacity (c= )
The energy required per unit mass of the substance to raise the temperature by 1K.
E = mc🔺T
