When zinc is placed in hydrochloric acid, a gas is produced. when the gas is collected in a tube and a lit match is placed in the tube, a pop is heard. this is a test for hydrogen gas. what can be concluded from this observations. a) a change in state has occurred. b) the zinc metal was turned into hydrogen gas. c) a chemical change has occurred producing the hydrogen gas. d) a physical change has occurred producing the hydrogen gas.

Supongamos que estás estudiando dos estrellas. ambas estrellas tienen la misma magnitud aparente, pero la estrella a tiene una magnitud absoluta mayor que la estrella b. ¿que puedes decir acerca de la distancia a la tierra de estas dos estrellas?

Select the correct text in the passage. which sentences describe examples of sustainable living? i live in an old apartment building downtown, but my company is based in an office park on the outskirts of the city. i drive an old car that needs to be replaced. i plan to buy a hybrid for better gas mileage, but for now i am able to carpool with a couple of friends from work. the drive to the office park is about 45 minutes each way, but we do get to work in a modern building. the architects just received a leed certification for the design.

12. calculate the hydroxide ion concentration of a solution with ph = 3.25. show all calculations leading to an answer