Chemistry Paper 1 (2)

  • Created by: KateS03
  • Created on: 22-04-19 14:00
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  • 2. Bonding, Structure & Properties of Matter
    • states of matter
      • aqueous means dissolved in water
      • how strong the forces are depend on: the material, pressure, and temperature
      • solids: strong forces of attraction, which holds them close together in fixed positions to form a regular lattice arrangement, they don't move so keep the shape, the vibrate around fixed position, the hotter, the more vibration causing a slight expansion
      • liquids: weak forces of attraction so they can flow, but stick close to each other, the particles move constantly in a random motion, the hotter, the faster they move causing a slight expansion
      • gases: very weak forces of attraction so they are free to move & are far apart, the particles travel in a straight line, they don't keep a shape but fill containers, the particles move constantly in random motion, the hotter, the faster meaning an expansion or a pressure increase
    • ionic bonding
      • metal & non-metal react together: metal loses electrons (positively charged), non-metal gain electrons (negatively charged)
      • the oppositely charged ions are strongly attracted to one another by electrostatic forces - ionic bond
      • dot & cross diagrams show how ionic compounds are formed
      • dot & cross are useful to show how they are formed, but don't show the structure, the size or how they are arranged
    • allotropes of carbon
      • fullerenes are shaped like closed tubes or hollow balls, atoms are shaped like: hexagons, pentagons or heptagons, they can cage other molecules (deliver drug) & large surface area for industrial catalysts & lubricants
      • graphene is a sheet of carbon, it is one atoms thick so a 2D compounds, bonds make it strong, its light so can be added to composite materials to improve strength, it can conduct as there is free electrons
      • fullerenes can form nano-tubes - tcarbon cylinders, ratio of length & diameter is high, conduct electricity & heat, high tensile (stretch) strength
      • graphite has a hexagonal sheets as the carbon only forms three covalent bonds, it is soft & slippery (lubricating) as the layers are only held together weakly so they can move over each other, hmp as the bonds need energy to break, it conducts electricity as there is a delocalised ion
      • diamond has a gcs, made up of carbon atoms that each form four covalent bonds making it really hard, the bonds take a lot of energy to break so it has a very hmp & it doesn't conduct as there is no free ions
      • nanotechnology uses nano-tubes in electronics or to strengthen without adding much weight e.g. tennis rackets
    • formation of ions
      • ions are charged particles, made when atoms lose or gain electrons
      • group 1 & 2 are the most likely to lose electrons to form positive ions (cations)
      • group 6 & 7 are the most likely to gain electrons to form negative ions (anions)
    • metallic bonding
      • the electrons in the outer shell of the metal atoms are delocalised which produce all the properties of metals
      • there are strong forces of electrostatic attraction between the + ions & - electrons, these forces hold atoms together in a regular structure (metallic bonding)
      • the forces are strong so need lots of energy to be broken so are solid at room temperature
      • delocalised electrons mean they are good conductors of heat and electricity
      • most metals are malleable as the layers of atoms can slide over each other
      • pure metals are often not right for jobs, so they  are mixed with other metals to make them harder (an alloy), different atoms are different sized so the alloys will distort the layers, making it harder for them to distort the layers
    • uses of nanoparticles
      • they could help make new catalysts
      • they can be used in nanomedicine as tiny particles are easier to absorb so they could deliver drugs
      • some conduct electricity so can be used in tiny electric circuits for computer chips
      • silver nanoparticles have antibacterial properties so can be added to polymer fibres to make surgical marks, wound dressing and deodorants
      • they can be used in cosmetics such as to improve moisturisers without making them really oily
      • it is not known how they affect the body, so some people are worried that the effects haven't been investigated properly and we don't now the long term impacts on health
      • they are used in sun creams and better protect against UV rays but its not clear if they damage cells or damage the environment
    • polymers & giant covalent structures
      • polymers are long chains of repeating units, they are joined by strong covalent bonds, the intermolecular forces are larger than simple covalent molecules so more energy is needed to break them
      • they have lbp than ionic or giant molecular compounds in general
      • in giant covalent structures, all the atoms are bonded to each other by strong covalent bonds
      • giant structures have very hmp & hbp as lots of energy is needed to break the bonds, they don't conduct electricity as they don't contain charged particles
      • giant structures include: diamond, graphite & silicon dioxide (which is what sand is made of, each giant is one giant structure of silicon and oxygen
    • ionic compounds
      • ionic compounds have a structure called a giant ionic lattice, the ions are closely packed in a regular lattice arrangement & have strong electrostatic forces of attraction in all directions
      • they all have hmp & hbp due to the many strong bonds which take a lot of energy to overcome
      • when they are solid they cant conduct electricity as the ions are held in place, but when they melt, the ions are free to move so they can carry an electric current
      • they dissolve easily in water as the ions separate & are free to move, so they'll carry a current
      • ball & stick models show the pattern of an ionic crystal and how the ions are arranged, but it isn't to scale & there aren't gaps
    • changing state
      • 1. when a solid is heated, its particles gain more energy making the particles vibrate more, weakening the forces holding them together
      • 2. at a certain temperature (melting point), particles break free as the particles have enough energy - melting from a solid to a liquid
      • 3. when a liquid is heated, the particles get even more energy making the particles move faster weakening and breaking the bonds
      • 4. at a certain temperature (boiling point), particles have enough energy to break their bonds - boiling from a liquid to a gas
      • 5. as a gas cools, the particles no longer have the energy to overcome the forces of attraction between them so bonds form
      • 6. at the boiling point, so many bonds have formed between the particles - condensing from a gas to a liquid
      • 7. when a liquid cools, the particles have less energy, so move around less, there is not enough energy to overcome the attraction between the particles so more bonds form
      • 8. as the melting point, so many bonds have formed between the particles that they are held in place - freezing from liquid to solid
      • the amount of energy needed for a change of state depends on how strong the forces between particles are
    • nanoparticles
      • coarse particles (dust) have a diameter between 2500 nm (2.5 x 10-6m) and 10000 nm (1 x 10-5m)
      • fine particles have a diameter beteen 100 nm (1 x 10-7m) and 2500 nm (2.5 x 10-6m)
      • nanoparticles have a diameter between 1 nm (1 x 10-9m) and 100 nm (1 x 10-7m)which only contain a few hundred atoms
      • nanoparticles have a large surface area to volume ratio this can cause the properties of a material to be different depending on weather it is a nanoparticle or in bulk
    • simple molecular substances
      • they are made up of molecules containing a few atoms joined together by covalent bonds
      • hydrogen H2 - often forms single covalent bonds with another hydrogen or another element to fill the first outer shell of 2
      • chlorine Cl2 - only needs one more electron so two chlorine atoms share & form a single covalent bond
      • oxygen O2 - shares two pairs of electrons with another oxygen to fill the outer shell
      • nitrogen N2 - needs three more electrons so shares three pairs with another nitrogen atom creating a triple bond
      • methane CH4 - carbon has four outer electrons so it can form four covalent bonds with four hydrogen atoms
      • water H2O - the oxygen shares a pair of electrons with two hydrogen atoms to form two single covalent bonds
      • hydrogen chloride HCl - both atoms only need one more electron to fill the outer shell so one bond is formed
      • substances containing covalent bonds usually have simple molecular structures: strong covalent bonds but weak attraction, lmp as intermolecular forces are weak, bigger molecules have stronger forces, don't conduct as they aren't charged
    • covalent bonding
      • when non-metals bond together, they share a pair of electrons to make a covalent bond
      • the positively charged nuclei are attracted to the shared pair of electrons by electrostatic forces making the bonds strong
      • atoms only share in the outer shells & each bond provides one shared electron for each atom, once the outer shell is full, they are very stable
      • dot & cross diagrams show the bonds, but they don't show the size of the atoms or how they are arranged
      • the displayed formula shows how atoms are connected in large molecules, but they don't show the 3D structure or which atoms the electrons come from
      • 3D models show the atoms, covalent bonds & arrangement, but they can be confusing & don't show where the electrons have come from

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