Monday, April 22, 2013

Feynman lectures in physics: Ch1 - Atoms in motion

I am reading this lecture series and putting together a summary of the information in there. This is my own interpretation and a few things could be amiss. Please use your own judgement.

  • Experiment is the sole judge of scienti c truth
  • Mass increases appreciably as velocity nears speed of light. Mass is not always constant.
  • Water has two atoms of hydrogen and one atom of oxygen forming a molecule.
  • Intermolecular forces keep the substance together. When you heat something the distance between molecules increases.
  • Force = pressures area
  • Volume of ice (and some type metals) decreases when melted (unlike most substances) to water because the crystaline structure in ice has a lot of "holes decreasing the packing density.
  • Why does a liquid cool as it evaporates: Molecues that had max energy leave the liquid during evaporation, so the ones left are the ones with lesser energy. Hence you blow on the soup to cool it.
  • Ion is an atom which has few extra electrons (than protons) of few electrons less.
  • Molecules exists only for certain substances. No molecules in salt, but there are molecules in water.
  • Why burning generates heat and light: Carbon attracts oxygen a lot causinga snapping together of atoms, generating kinetic energy. Ordinarily seen in molecular motion of hot gas, but sometimes too much energy is also seen in the form of light (flames).
  • Organic chemistry is useful to discover arrangement of atoms by mixing substances and checking color for example.

Sunday, April 21, 2013

Does blowing air on a spoon of hot soup cool it?

As explained by Fenyman way back in 1960s, blowing acually speeds up evaporation from the surface of a hot liquid, causing molecules with more energy to leave the liquid and not return back. This decreases overall energy (and heat) in the liquid.

Beware this may reduce the overall soup you drink though :)