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C2.2 Flashcards
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- 1Why do ionic solids have high melting points?They have giant structures with strong electrostatic forces that hold the ions together and a lot of energy is needed to overcome the forces
- 2Why can ionic substances conduct electricity when molten or when dissolved in water?The ions can move freely and carry the charge
- 3Why does petrol not conduct electricity?The molecules in petrol have no overall charge
- 4Why are substances with large molecules more likely to be liquids or solids at room temperatures?The intermolecular forces are greater for larger molecules
- 5Why do substances with giant covalent structures have very high melting points?Every atom is joined to several other atoms, many strong covalent bonds have to be broken and so it takes a large amount of energy to melt the giant structure
- 6Give 2 similarities between diamond and graphiteForms of carbon; giant covalent structures or covalent bonding
- 7Give 2 differences between diamond and graphiteCarbon atoms in diamond are bonded to four other carbon atoms, only to three other atoms in graphite; diamond is three dimensional, graphite is opaque; graphite is a good conductor of electricity, diamond is a poor conductor; graphite has delocalised electrons, diamond does not, graphite has intermolecular forces, diamond does not
- 8Give 2 similarities between graphite and fullerenesForms of carbon, hexagonal rings of atoms
- 9Give 2 differences between graphite and fullerenesGraphite is a giant structure, fullerenes are molecules; graphite is two dimensional, fullerenes are three-dimensional/cage like; graphite forms large particles, many fullerenes are nano -sized
- 10Why can metals be made into wires?When stretched, the atoms slide into new positions without breaking apart
- 11Give two reasons why alloys can be more useful than pure metalsWhen stretched, the atoms slide into new positions without breaking apart
- 12Why are metals good conductors of electricity?Delocalised electrons move rapidly through the metal structure
- 13Why do LD and HD poly(ethene) have different properties?They are made using different reaction conditions; they have different structures or differently shaped molecules
- 14What is the main difference in the structures of thermosoftening and thermosetting polymers?Thermosoftening polymers have no cross-links or no covalent bonds between the polymer chains, thermosetting polymers have cross-links
- 15What allows thermosetting polymers to be remoulded?The weak intermolecular forces between the chains (are overcome by heating)
- 16What is a nanoparticle?A very small particle that is a few nanometers in size, or made of a few hundreds of atoms
- 17Scientists have developed a new deodorant containing nanoparticles. What should be done before it is sold for people to use?Its effects on people and the environment should be researched/tested (to ensure it is safe to use)
- 18Why does it take a lot of energy to melt sodium chloride?It has a giant ionic structure with strong electrostatic forces/bonds that hold the ions firmly in position and that need a lot of energy to overcome/break them
- 19Why are compounds like methane, CH4 and ammonia, NH3, gases at room temperature?They are made of small molecules or covalent bonds act only between the atoms within a molecule
- 20Polymers made from different monomers have different properties. Explain whyDifferent monomers change the structure of the polymer chains or the polymer chains have different shapes or structures
- 21Some dental braces are made from shape-memory alloys. What is meant by a 'shape-memory alloy'?An alloy (mixture of metals) that can be bent/deformed and changes back to its original shape when heated
- 22Explain why diamonds are very hardEvery carbon atom is covalently/strongly bonded to four other carbon atoms in a giant (3-D) covalent structure
- 23Why do ionic compounds need to be molten or in solution to conduct electricity?The ions cannot move in the solid, but become free to move in the molten liquid or in solution
- 24Explain why a block of copper can be hammered into a sheetThe atoms are in layers. The layers slide over each other, into the new shape, without breaking apart
- 25Silver nanoparticles are used in some socks to help prevent bad smells How are silver nanoparticles different from ordinary silver particles?They are very much smaller, have a much greater surface area
- 26Suggest why a sock manufacturer would use nanoparticles instead of ordinary silver particlesThey are more effective (because of their greater surface area), needs to use much less silver (so it is cheaper), easier to attach to sock fibres
- 27Explain why thermosetting polymers are often used to make handles for cooking pansThey do not soften/melt when they get hot, they are good insulators (of heat), they can be moulded into shape but then are rigid/hard
- 28Explain how the atoms in a metal are bonded to each otherThe outer electrons delocalise, leaving a lattice of positive ions; the delocalised electrons strongly attract the positive ions and hold them in position
- 29Why can graphite conduct electricity?There are delocalised electrons in graphite or one electron from each carbon atom is delocalised; the delocalised electrons carry the electrical charge
- 30Explain what is meant by 'intermolecular forces'Forces between molecules (that are much weaker than covalent bonds within the molecules)
- 31C60 is a fullerene. What are fullerenes?Forms of carbon, with large molecules, based on hexagonal rings of carbon atoms, often cage-like structures, can be nano-sized, have many useful applications
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- GCSE (Unit 2) Chemistry Fichas sobre C2.2 Flashcards, creado por Mel Hughes el 25/08/2016.
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- Mel Hughes
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