Jon- Your description of air and your definition of mixtures are good. However, we were asked why we believe that air is a mixture. In other words, we were asked for evidence. The sort of facts you cite were not discovered by reading textbooks but by doing real experiments.
Ingroup bias, sometimes known as in-group favoritism, in-groupâout-group bias or intergroup bias, refers to a pattern of favoring members of oneâs in-group over out-group members.This can be expressed in evaluation of others, allocation of resources and many other ways.ngroup bias, sometimes known as in-group favoritism, in-groupâout-group bias or intergroup bias, refers to a pattern of favoring members of oneâs in-group over out-group members.
1 The bias of an estimator is the difference between an estimator's expectations and the true value of the parameter being estimated.  Omitted-variable bias is the bias that appears in estimates of parameters in a regression analysis when the assumed specification omits an independent variable that should be in the model.