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16 Cards in this Set
- Front
- Back
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What are the properties of an amorphous substance? Give on example of an amorphous substance.
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Amorphous solids have no regular shape. Examples: glass, plastics, rubber
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What types of substances have high surface tension when a liquid? Why?
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Any substances with strong bonds have high surface tension because particles pull together strongly.
WEAKEST: dispersion< dipole-dipole < H-bonding < metallic or ionic STRONGEST |
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Explain how it is possible for non-polar molecules to be attracted to each other.
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By chance, more electron density can be found on one side of a molecule. Thus, an instantaneous dipole forms. This instantaneous dipole induces another dipole in a neighboring molecule (e- are repelled to other side). Now the two molecules attract due to partial charges. However, it is only a temporary attraction
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What are the principle differences in structure between a solid made up of nonpolar molecules and a network covalent solid? How do their properties differ from each other?
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Non-polar covalent molecules—distinct molecules that are attracted to each other by dispersion bonds
Low mp and bp because dispersion bonds are easy to break. Soft. Network covalent-- all single atoms in a network that are all connected by covalent bonds (no mc’s) High mp, hard and brittle |
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If a substance mixes with nonpolar, slightly polar and polar substances, this substance would best be characterized as being
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slightly polar
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Why does graphite conduct electricity?
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Graphite is a network covalent solid containing all carbon atoms that are sp2 hybridized. Thus, every carbon has a p orbital which can overlap with a neighboring p orbital. Thus, there is a network of pi bonds throughout the lattice. Electrons are held weakly in pi bonds, so electrons are free to move throughout the network of p orbitals.
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Why do ionic compounds have higher melting points than polar covalent molecules? (HINT: charges)
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To melt ionic compounds, ionic bonds must be broken. These are strong bonds because it is an attraction between full charges.
To melt polar covalent substances, dipole-dipole bonds or H-bonds must be broken. These are weaker attractions because it is an attraction between partial charges. |
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Three important properties of water are listed below. Give basic reasons for each important property. Then, explain why each property is so important to life, the environment and to scientists.
1) relatively high boiling point 2) ice is less dense than liquid water 3) dissolves in a very large variety of substances |
1Compared to other molecules, water has relatively strong intermolecular forces. It does H-bonding which is stronger than dipole-dipole and dispersion. Thus, water’s boiling point is relatively high—making it a liquid at room temperature.
It is beneficial to have water as a liquid because liquids are great for transport and great as solvents. 2When water molecules come together in a solid, they arrange themselves in a “hexagonal” pattern. This makes the molecules spread out from each other, so ice is less dense than liquid water. Ice floats on liquid water. Thus, the top layer of ice can insulate the water below and keep it from freezing. This prevents our lakes from freezing solid each winter. 3Water is very polar, so it dissolves everything except the non-polars. (It can dissolve ionics and polars) Since so many compounds dissolve in water, --water is useful for transporting nutrients (in bodies and oceans) -- water is a great solvent for industrial processes (Ex: chemical reactions) -- However, this is also dangerous because our water supply can easily be contaminated by toxins. |
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what's is water often referred to as because it dissolves in a large variety of substances
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the universal solvent
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Dispersion
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momentary dipoles occurring due to uneven electron distributions in neighbouring molecules as they approach one another
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Dipole Dipole Bonding
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occur between molecules that have permanent net dipoles
partial positive---partial negative |
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Hydrogen bonding
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occur between molecules that have a permanent net dipole resulting from hydrogen being covalently bonded to either fluorine, oxygen or nitrogen
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The larger the size of a molecule will make the bp and melting point higher or lower?
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higher
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fullerene
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Any of various carbon molecules that are nearly spherical in shape, are composed of hexagonal, pentagonal, or heptagonal groups of atoms, and constitute the third form of pure carbon after diamond and graphite.
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amorphous substances
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no definite shape
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entropy
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disorder-molecules mix
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