You are dating moon rocks based on their proportions of uranium-238 (half-life of about 4.5 billion years) and its ultimate decay product, lead.

1. find the age for a rock for which you determine that 55% of the original uranium-238 remains, while the other 45% has decayed into lead.

2. find the age for a rock for which you determine that 68% of the original uranium-238 remains, while the other 32% has decayed into lead.

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

The wave shown on the electromagnetic spectrum disturb the medium it passes through a)different frequency. b)the same frequency .

Select all that apply. a beta particle: is electromagnetic energy is an electron has zero charge is emitted from the nucleus has a +2 charge has a -1 charge