The chemical structure of the water molecule facilitates life

Atoms bond to form molecules and compounds.

- Molecules = Combinations of two or more atoms
a. Oxygen gas = O2

- Compounds = A molecule composed of atoms of two or more different elements
a. Water = two hydrogen atoms bonded to one oxygen atom: H20
b. Carbon dioxide = one carbon atom with two oxygen atoms: CO2

- Covalent bond = atoms in a molecule share electrons
a. For example, the atoms that bond to form H20

- Polar covalent bonds = Atoms share electrons unequally, with one atom exerting a greater pull
a. The oxygen in a water molecule attracts electrons

- Ionic bonds = an electron is transferred from one atom to another
a. Are not molecules, but are salts, such as table salt, NaCl

- Solutions = no chemical bonding, but is a mixture of substances (i.e., blood, oil)

- Hydrogen bond causes oxygen from one water molecule to be attracted to the hydrogen atoms of another
a. Water’s strong cohesion allows nutrients and waste to be transported
b. Water absorbs heat with only small changes in its temperature, which stabilizes systems