Read more about the properties of water here. Molecules and ions dissolve in water when they are more attracted to the partial charges on the water molecules than they are to each other. Here is a video that that explains the energy involved in the dissolving process. Molecules must have an unequal distribution of electrons or be "polar" in order to be attracted to water molecules. In order for a molecule to be polar it must have polar bonds. When atoms with substantially different electronegativities bond together a polar bond is formed. Some molecules like carbon dioxide are non polar even though they have polar bonds. This is because the symmetry of the carbon dioxide molecule is linear. The result is that a carbon dioxide molecule does not have positive and negative ends and does not easily dissolve in water.
Grease is made up of nonpolar molecules which is why you need soap to help grease dissolve in water. Soap molecules have a polar end that likes water and a nonpolar end that likes grease. Click here to see an video showing how soap works.
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| Hexane (green = carbon, white = hydrogen) |
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| Ethanol (green = carbon, white = hydrogen, red = oxygen) |
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| Potassium chloride (purple = potassium, green = chloride ions) |
After watching the video and reading more about the properties of water, answer the following questions:
1. Do you think hexane pictured above left will dissolve in water? Explain your reasoning.
2. Do you think ethanol pictured above right will dissolve in water? Explain your reasoning.
3. Do you think potassium chloride pictured above center will dissolve in water? Explain your reasoning.
4. Chemists often refer to water as "the universal solvent". Explain what you think this means.
Your answers should be a minimum of 3-5 complete sentences for each questions and should include the following chemistry terms:
polar covalent
nonpolar covalent
ionic
ion
electrostatic attraction
dissociate
2. Do you think ethanol pictured above right will dissolve in water? Explain your reasoning.
3. Do you think potassium chloride pictured above center will dissolve in water? Explain your reasoning.
4. Chemists often refer to water as "the universal solvent". Explain what you think this means.
Your answers should be a minimum of 3-5 complete sentences for each questions and should include the following chemistry terms:
polar covalent
nonpolar covalent
ionic
ion
electrostatic attraction
dissociate
