Chemistry 0.0 / 5 ? ChemistryAtoms and compoundsStructure and bondingOrganic ChemistryEnergeticsRates of ReactionsReversible reactionsIGCSEEdexcel Created by: mariakholCreated on: 18-05-16 13:01 why does the number of protons = number of electrons in an atom it makes the atom neutral, as atoms have no charge 1 of 21 why are metal ions positively charged and non-metal ions are negatively charged? metal ions lose electrons and non-metal ions gain electrons 2 of 21 why do ionic compounds have high melting points? strong electrostatic forces of attraction between oppositely charged ions in a giant lattice 3 of 21 why do ionic compounds only conduct when they are liquids? the lattice breaks, so the ions are free to move 4 of 21 why do covalent molecules have low melting points? intermolecular bonds are weak; takes little heat energy to break them 5 of 21 why do covalent structures not conduct electricity? no charged particles free to move 6 of 21 why do metallic structures have high melting points? strong electrostatic force of attraction between sea and positive metal ions in giant lattice 7 of 21 why are metallic structures malleable the layers of ions slide over each other and are still attracted to the sea in the new position 8 of 21 why do metallic structures conduct electricity? sea of delocalised electrons - charged, free to move 9 of 21 why does graphite conduct electricity and diamond doesn't? graphite has delocalised electrons and diamond doesn't 10 of 21 why is graphite used as a lubricant? weak force of attraction between the layers, so the layers can slide over each other 11 of 21 why are small molecules produced at the top of the fractionating column? they have low melting points 12 of 21 why is there a need to carry out cracking reactions? longer alkanes (lubricants) are in less demand than shorter alkanes (fuels) 13 of 21 fossil fuels should be used sparingly because... non-renewable, produce co2 will take a long time to recover as comes from fossilised organisms 14 of 21 fuels should be burned with enough oxygen so that... it completely combusts no CO or C produced 15 of 21 why is disposal of polymers a problem? burn - produce greenhouse gas; bury - space; takes up space and energy 16 of 21 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 17 of 21 why do endothermic reactions need heat energy more heat energy is released when making the bonds than was taken in when they broke 18 of 21 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 19 of 21 why do reactions need activation energy energy needed to break bonds in reactants before new ones form 20 of 21 why does temperature affect rate of reaction increase in the number of high energy collisions - more successful collisions 21 of 21
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