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Chapter 5, Lesson 4 Multimedia

Sucrose

Two representations of a sucrose molecule. At left, a ball-and-stick model, with plus and minus signs to indicate areas of slight positive and negative charge. At right, a space filling model of sucrose, also with areas of positive and negative charge designated by plus and minus signs.Two space-filling models of sucrose molecules closely associated with one another, based on their corresponding areas of positive and negative charge.
  • The ball-and-stick and first space-filling model show that sucrose is a large molecule made up of carbon, oxygen, and hydrogen.
  • Sucrose has many O–H bonds which are polar.
  • These polar areas are shown with a + near the hydrogen atom and a − near the oxygen atom.
  • The second space-filling model shows two sucrose molecules held together by their opposite polar areas.
  • These molecules will separate from each other when sucrose dissolves.

Water Dissolves Sucrose

Two space-filling models of sucrose are closely associated amidst a large number of water molecules.Next, the association between the two scurose molecules is lessened as they water molecules begin to compete with their attraction for each other. The two sucrose molecules move even further apart, as the attractions between the water molecules and sucrose molecules overcome the attractions between the sucrose molecules. The two sucrose molecules are very far apart, as the water molecules surround them .
  • Water molecules arrange themselves around the sucrose molecules according to opposite polar areas.
  • The attraction of the water molecules and their motion overcome the attraction between sucrose molecules.
  • The sucrose molecules dissolve as they are separated from the other molecules and mix into the water.

Sucrose

A ball and stick model of a sucrose molecule changes into a charge-density model of sucrose, showing its areas of slight positive and negative charge.

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  • The sucrose molecule has many oxygen-hydrogen (O–H) bonds which are polar.
  • The charge-density model shows the positive ares near the hydrogen atom as blue and the negative area near the oxygen atom as red.
  • The sugar molecules are attracted and held together in a crystal by these opposite polar areas.

Water Dissolves Sucrose II

Several molecules of water are attracted to sucrose molecules, due to their corresponding areas of slight positive and negative charge. When the attractions between the sucrose molecules and water overcome the attraction that the sucrose molecules have for themselves, the sucrose dissolves.

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  • Water molecules arrange themselves around the sucrose molecules according to opposite polar areas.
  • The attraction of the water molecules and their motion overcome the attraction between sucrose molecules.
  • The sucrose molecules dissolve as they are separated from each other and mix into the water.

Water, Alcohol, and Oil

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. A space-filling model of a non-polar molecule, which has no areas of slight positive and negative charge.
  • The water is polar so it dissolves the polar color and sugar.
  • The alcohol has a polar area but a larger non-polar area. It is not a good dissolver of color or sugar.
  • The oil is non-polar and does not dissolve the color or sugar.

Citric Acid

A ball-and-stick model of citric acid.
  • This is a ball-and-stick model of citric acid.
  • Citric acid is dissolved in water in oranges, lemons, grapefruit and other citrus fruits.
  • Citric acid dissolves very well in water.