¿POR QUÉ SE LE LLAMA INDICADOR UNIVERSAL AL PAPEL p H? ¿DE QUÉ ESTÁN HECHOS LOS ELECTRODOS DEL POTENCIÓMETRO?
SI LA SALIVA HUMANA TIENE NORMALMENTEUN p H DE 7.4 (CASI NEUTRO) ¿QUÉ SUCEDE
CUANDO DISMINUYE, ES DECIR CUANDO LA SALIVA SE VUELVE ÁCIDA?

Achemical reaction (also known as a chemical change) produces substances that are chemically different from the starting materials. an example of a chemical reaction is the formation of water from hydrogen and oxygen gas. in a physical change, a substance changes its physical appearance but not its chemical identity. an example of physical change is the formation of liquid water from solid water, a familiar process called melting. physically, liquid water looks very different from solid water (ice) but the chemical identity, water, is the same for both. which of following changes that affect the composition of our atmosphere involve physical changes and which involve chemical reactions? oxygen gas changes to ozone during thunderstorms carbon dioxide is produced by the combustion of gasoline in an automobile engine. when coal, oil, and natural gas are decomposed in landsills they produce methane gas. freezing rain develops when a warm air mass overrides a cold air mass. fog forms from water vapor when the temperature drops below the dew point

An object becomes electrically charged when: electrons are created in it electrons from it are destroyed electrons are transferred to it protons from it are destroyed protons are created in it

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms