Solution for Homework #1
2.
Sun
Moon
Earth
New Crescent Nearly full Full
5. Follow a planet every night until it noticeable brightens or dims--an indication that it is closer
to or further from Earth.
8. See Figure 1.15. Mars appears "full" when it is farthest from Earth (directly on the far side
of the sun), and also when it is closest to Earth. At other times, Mars appears less-than-full,
but you will never see a "new Mars" or even a "crescent Mars." So Mars goes through partial
phases, but not complete phases.
17. Move the thumbtacks far apart.
29. 100 billion times 100 billion = 10,000,000,000,000,000,000,000 (a one followed by 22
zeros).
33. It exploded about 3500 years before 1054 A.D., or in about 2446 B.C.
Ch 2
8. Pure water is pure H2O, a pure compound. Oxygen gas is O2, containing only the element
oxygen (O), so it is an element. Liquid mercury (or any other form of mercury) is made of
only one element, mercury, so it is an element. H2SO4 (also called "sulfuric acid") is a
compound. U is an element. Air is a mixture of many different compounds and elements:
N2, O2, A (Argon), H2O, etc. He is an element. Carbon dioxide, CO2, is a compound. H2
and H are both elements (hydrogen, although of two different molecular forms: two-atom
and single-atom).
16. Assume that coal is pure carbon (C). When coal burns, each C atom attaches to two O atoms
to make CO2. If we assume, for simplicity, that C and O atoms have the same weight, then a
CO2 molecule would weigh three times as much as a single C atom. So a ton of coal makes
