15.1 Boltzmann Factor Flashcards
Describe two things we do to prevent bacteria from changing tissues.
We store food in freezers to prevent bacterial action from destroying organic materials and for particularly sensitive biological samples such as stem cells, we store these at the temperature of liquid nitrogen, 77K, (cryogenic storage), to deny bacteria energy to change tissues.
What’s the formula for energy per particle? Why is it changed?
In ideal gases intermolecular interactions are negligible so particles have no potential energy and mean energy per particle is 3/2 kT. Similar expressions can be found for vibrating atoms in a solid of photons emitted by a hot object. This is mean energy, but we only need an order of magnitude value so E=kT.
What is k in E=kT?
K = Boltzmann constant which is 1.38*10^-23
What’s activation energy?
For many processes activation energy is required for them to happen, E. In chemistry reagants need to be heated giving enough kinetic energy for molecules to have a reaction. Reactants have energy less than this, and this is an exothermic reaction.
What are reactions which need energy?
Water needs thermal energy to evaporate.
In nuclear fusion reactions in the Sun’s core only occur due to the temperature of many million Kelvin.
Variation of resistance with temperature in thermistors is due to thermal ionisation in the semiconductor lattice.
Why is E much greater than kT sometimes for ratio E/kT?
Energy needed to liberate one particle can be much greater than energy per particle, (ie- E/kT). For wet clothes hanging, some high energy particles can escape the surface and the mean energy of the water molecules will fall. Newly cooled water will gain energy by collision with other warm particles in the environment, allowing more to be liberated until all water has evaporated.
