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BONDING, STRUCTURES, POLYMERS AND NONSCIENCE
practice exam questions
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nanosciencejpg2 (image/jpg)
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| What is a Covalent Bond? | A bond where two or more atoms share electrons from their outer shells |
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Draw an ammonia atom
(hint: nitrogen (below) and hydrogen)
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NitrogenAtom (image/jpg)
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Image:
diag_ammonia.gif (image/gif)
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| How many neutrons are there in an atom of gold? | 118 |
| How does a gold atom become a gold ion? | It loses electrons |
| Balance this equation: ......CO + ...... = ......CO2 | 2CO + O2 = 2CO2 |
| Why does Carbon Dioxide have a very low boiling point? | -It has small molecules -Intermolecular forces between molecules -Small amount of energy needed to break molecules |
| Why is gold still used in industrial processes? | -It is very reactive and so is a good catalyst -It's a good conductor of heat and electricity -It's malleable and ductile |
| What experiment, on its own, cannot fully answer one of the following questions: -How much Carbon dioxide is produced when 100kg of kelp is burned? -Will kelp last longer than coal as an energy source? -Does kelp give out more heat energy than coal? | Will kelp last longer than coal as an energy source? |
| Why can't scientists answer: 'should people use kelp instead of coal as an energy source'? | -Cannot be determined by an experiment -Based on opinion |
| How many electrons are there in the outer shell of an iodine atom? | 7 |
| What happens when sodium atoms react with iodine atoms to produce sodium iodide? | -The sodium atom needs to gain an electron and the iodine needs to gain one for a full outer shell -Sodium gives an electron to iodine, so both original atoms have full outer shells and are ions -The iodine ion becomes sodium iodide and is negatively charged |
| Why does sodium iodide SOLUTION conduct electricity? | It is in liquid form so the electrons are free to move around and can therefore conduct |
| Why is silicon dioxide a suitable material for lining furnaces? | -It has a giant covalent structure, meaning that there are extremely strong bonds between the oxygen ans silicon atoms -It has a very high melting point as it takes a very high temperature to melt it, so the iron in the furnace can be melted without fear of the furnace melting in the process |
| Why is graphite SOFTER than diamond? | -The layers of graphite can slide over each other because there are weak forces between the layers -Each diamond atom is strongly bonded to 4 others so the atoms cannot slide over eachother |
| Graphite conducts electricity, diamond does not EXPLAIN WHY | -Graphites electrons are free to move, meaning that it can conduct easily -Diamond is much harder, with strong bonds, and so is unable to conduct electricity as its electrons cannot separate to do so |
| Describe the structure of a metal | Atoms are in a regular structure, held together by strong electrostatic forces. They have a sea of electrons which are free to move |
| Why are metals good conductors of heat? | They're electrons are free to move |
| How are nanosized particles different from normal sized particles? | They are much smaller |
| Suggest one reason why nanosized particles of silver might help to transfer heat better than normal sized particles? | They can fit into smaller gaps than normal sized particles and will have less space between them |
| Why would Thermosoftening Polymers not suitable for packaging very hot foods | They would not melt as they have a low boiling point because there are weak forces between the atoms |
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