Chemistry

why does the number of protons = number of electrons in an atom
it makes the atom neutral, as atoms have no charge
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why are metal ions positively charged and non-metal ions are negatively charged?
metal ions lose electrons and non-metal ions gain electrons
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why do ionic compounds have high melting points?
strong electrostatic forces of attraction between oppositely charged ions in a giant lattice
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why do ionic compounds only conduct when they are liquids?
the lattice breaks, so the ions are free to move
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why do covalent molecules have low melting points?
intermolecular bonds are weak; takes little heat energy to break them
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why do covalent structures not conduct electricity?
no charged particles free to move
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why do metallic structures have high melting points?
strong electrostatic force of attraction between sea and positive metal ions in giant lattice
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why are metallic structures malleable
the layers of ions slide over each other and are still attracted to the sea in the new position
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why do metallic structures conduct electricity?
sea of delocalised electrons - charged, free to move
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why does graphite conduct electricity and diamond doesn't?
graphite has delocalised electrons and diamond doesn't
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why is graphite used as a lubricant?
weak force of attraction between the layers, so the layers can slide over each other
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why are small molecules produced at the top of the fractionating column?
they have low melting points
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why is there a need to carry out cracking reactions?
longer alkanes (lubricants) are in less demand than shorter alkanes (fuels)
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fossil fuels should be used sparingly because...
non-renewable, produce co2 will take a long time to recover as comes from fossilised organisms
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fuels should be burned with enough oxygen so that...
it completely combusts no CO or C produced
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why is disposal of polymers a problem?
burn - produce greenhouse gas; bury - space; takes up space and energy
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why are energy change calculations not very accurate
data books results are averages; bonds don't take into account what else they are bonded to
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why do endothermic reactions need heat energy
more heat energy is released when making the bonds than was taken in when they broke
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why do exothermic reactions release heat energy
less energy is needed to break the bonds in the reactants than is released during the formation of the products
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why do reactions need activation energy
energy needed to break bonds in reactants before new ones form
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why does temperature affect rate of reaction
increase in the number of high energy collisions - more successful collisions
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Other cards in this set

Card 2

Front

why are metal ions positively charged and non-metal ions are negatively charged?

Back

metal ions lose electrons and non-metal ions gain electrons

Card 3

Front

why do ionic compounds have high melting points?

Back

Preview of the front of card 3

Card 4

Front

why do ionic compounds only conduct when they are liquids?

Back

Preview of the front of card 4

Card 5

Front

why do covalent molecules have low melting points?

Back

Preview of the front of card 5
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