1. describe the differences and similarities in how coal, oil, and natural gas formed. 2. describe what an oil sand is and explain the advantages and disadvantages associated with its use and extraction. 3.explain why a nuclear chain reaction is self-sustaining. 4. what is the most widely accepted model of how the solar system formed? explain how the solar system formed under this model.

An object of dimensions 50 cm x 40 cm x 0.20 cm has a mass 60g. find its density in g/cm3 and kg/ m3

Uranium has two naturally occurring isotopes. 238u has a natural abundance of 99.3% and 235u has an abundance of 0.7%. it is the rarer 235u that is needed for nuclear reactors. the isotopes are separated by forming uranium hexafluoride uf6, which is a gas, then allowing it to diffuse through a series of porous membranes. 235uf6 has a slightly larger rms speed than 238uf6 and diffuses slightly faster. many repetitions of this procedure gradually separate the two isotopes. what is the ratio of the rms speed of 235uf6 to that of 238uf6? express your answer to five significant figures.

The smallest particle of an element that retains its identity in a chemical reaction. true or false