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11 Cards in this Set
- Front
- Back
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Why do methane and water have such lower melting points than silicon carbide and silicon dioxide? |
Methane and water are covalent molecules so to melt these you only need to break weaker intermolecular bonds. But between silicon carbide and silicon dioxide there are strong covalent bonds as they are covalent networks |
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What are the 3 intermolecular forces from weakest to strongest? |
London Dispersion forces, Permanent dipole to permanent dipole interactions, hydrogen bonding |
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Describe how LDF arise? |
Movement of electrons can cause a temporary dipole in a molecule, temporary dipoles can induce dipoles on neighbouring molecules. The LDF is the attraction between temporary dipoles and induced dipoles. Very weak. |
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Why is sulfurs's melting point significantly higher than phosphorus? |
Although both sulfur and phosphorus have London Dispersion forces, the LDF are stronger in sulfur as the sulfur molecule has more electrons than phosphorus |
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What type of molecules have PD- PD interactions? |
Polar molecules |
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How can polarity cancel within a molecule? |
If its shape is symmetrical on two planes |
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How can a molecule be described as polar? |
When there is a significant difference in the electronegativity of the elements in the molecule |
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When is a molecule capable of hydrogen bonding? |
When hydrogen is bonded to Nitrogen, Oxygen or Fluorine |
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What can make a molecule more viscous? |
More hydrogen bonds |
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Describe the effect of hydrogen bonding on ice? |
Results in an expanded structure that causes the density of ice to be less than water |
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Why are polar molecules more soluble with water? |
As water is also polar and like is soluble with like. The polar molecule is soluble in the identically polar water |
