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Chapter 5, Lesson 1 Multimedia

Water Fountain

Several close-up shots of a water fountain.

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Water stays together because water molecules are attracted to one another.

Polar Water Molecule

Several representations of a water molecule, showing its areas of slight positive and negative charge and how they are distributed about the molecule.

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  • In the water molecule, the oxygen and hydrogen atoms share electrons in covalent bonds.
  • There are a total of 10 protons and 10 electrons so the water molecule is neutral.
  • The electron cloud model shows that electrons are not shared equally in the water molecule.
  • Electrons are a bit more attracted to the oxygen atom than they are to the hydrogen atoms.
  • This makes the water molecule slightly negative at the oxygen end and slightly positive at the hydrogen end.

Attraction Between Water Molecules

A charge density model of water, showing how the areas of slight positive charge in one water molecule attract the areas of slight negative charge in another water molecule.

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Water molecules tend to orient themselves with the positive area of one molecule near the negative area of another.

Attractions on Different Levels

The positively charged protons in one hydrogen molecule attract the negatively charged electrons in another hydrogen molecule, and vice versa.Even within a single atom, the electrons feel an attraction for the protons in the nucelus, which keeps them from floating away. Within a molecule, different types of atoms are attracted to one another because the negatively charged portions of one atom are attracted to the positively charged portions of another. A water molecule, with individual atoms represented using energy level models, and pairs of electrons deonting covalent bonds. Slight areas of positive and negative charge on individual water molecules attract one another.
  • Electrons are attracted to protons within an atom. This is what keeps the atom together.
  • Electrons are attracted to the protons of other atoms. This is what causes atoms to bond and what holds a molecule together.
  • Electrons can be shared unequally in a molecule, creating a polar molecule. Opposite polar ends of molecules attract and hold one molecule to another.

Water and Alcohol Molecules

A space-filling model of a water molecule, with plus signs near its hydrogens and minus signs near its oxygen atom, to indicate its areas of slight positive and negative charge.A space-filling model of a isopropyl alcohol, with plus signs near one of its hydrogens and minus sign near its oxygen atom, to indicate its areas of slight positive and negative charge.
  • Alcohol has one O–H bond which is polar but a large portion of the molecule is made up of C–H bonds which are nonpolar.
  • Alcohol molecules do not attract each other as strongly as water molecules and evaporate faster.

Water and Alcohol Boiling

Two thermometers, one submerged in water, the other submerged in alcohol, showing the alcohol boils at a lower temperature than water.
  • Alcohol has one O–H bond which is polar but a large portion of the molecule is made up of C–H bonds which are nonpolar.
  • Alcohol molecules do not attract each other as strongly as water molecules and boil at a lower temperature.