La leche agria es una cambio físico o químico ? aiuda

Select all of the statements which are true. electrons are located in shells or orbits around the atom. electrons orbit slowly around the atom. electrons travel in one flat path around the nucleus of an atom. the valence of an atom is determined by the number of electrons in the atom's outermost shell.

About 3% of the water on earth is freshest. only about 40% of that freshwater is available for human use. why is so much freshwater unavailable for human use?

Which is true about metals used for jewelry, such as platinum and gold? a. they have low flammability. b. they have low reactivity. c. they have high flammability. d. they have high reactivity.