ABSTRACT
Earth is the only planet in the solar system where water appears in solid, liquid, and vapor states at common temperatures. The existence of water on Earth has much to do with Earth’s size and distance from the Sun. Hydrogen (90%), helium (9%), and oxygen are the three most abundant elements in the universe, followed by neon, nitrogen, and carbon (Cox, 1989). Helium and neon are solitary elements. Two hydrogen atoms and one oxygen atom are easily bound to become water (H2O), three hydrogens join one nitrogen to become ammonia (NH3), and four hydrogens join one carbon to become methane (CH4). The melting points of H2O, NH3, and CH4 are 0°C, −78°C, and −183°C, respectively, while the boiling points are 100°C, −33°C, and −162°C.
