Astudent mixes two clear liquids together. after a few minutes, a white powdery solid can be seen settling on the bottom of the test tube. which of the following is a conclusion that the student can draw based on these observations?
a: the two liquids are toxic and should be handled with extreme caution.
b: the two liquids were pure substances before they were mixed.
c: the two liquids have been stored too long and are no longer good.
d: the two liquids have gone through a chemical change in which a new substance called a precipitate was produced.

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

What will most likely happen when two bromine atoms bond together?

How many protons, electrons, and neutrons are in each of the following isotopes? a. zirconium-90 b. palladium-108 c. bromine-81 d. antimony-123