The combining of hydrogen and oxygen gas into liquid water is an example of what kind of change?

phase
chemical
physical

Will give imagine you are given a mystery element. it is, however, a discovered and known element. you may perform a maximum of two observations or tests to determine its identity. time and money is critical, so you need to prioritize your tests. if you can get by with a single test, you get 100 super-geek points from your research lab team. pick your two tests, number them as #1 and #2, and justify why you think these two will certainly be enough (and why the first might well be enough all by itself.) the available tests are classification into metal, non-metal, or metalloid, count of valence electrons, count of electron shells, atomic radius (error range: +/- 1 pm), electronegativity (error range: +/- 0.1), first ionization energy (error range: +/- 10 kj/mole), melting point (error range: +/- 10 c), and boiling point (error range: +/- 20 c).