Weak Points - Yr 11 Mock

• Chemical formulas

  • Ammonia - NH3
  • Hydrochloric acid - HCl
  • Sulfuric acid - H2SO4
• Discoveries

  • Rutherford - nucleus
  • Chadwick - neutrons
  • Bohr - current model
• Periods

  • Rows on the periodic table
  • Tells us the number of shells on an element
• Group 2 metals are called alkaline earth metals. They are soft and have low melting points.
• The early periodic table:

  • Scientists tried to classify elements by arranging them by their atomic weights
  • Atomic weights are now called relative atomic mass
  • Mostly incomplete since there were many undiscovered elements and elements were also placed in groups with elements that weren't similar to them
• Dimitri Mendeleev's Periodic table:

  • He arranged the elements in increasing atomic weight
  • He also took into account the properties and their compounds
  • His periodic table had
  • Gaps within it
  • Elements with similar chemical properties lined up in groups
  • Because of this some elements that were next to each other were in the wrong order in terms of atomic weight
  • Mendeleev made predictions on the properties of the undiscovered elements in the gaps in his period table
  • When these elements were discovered, these predictions were correct
• • Liquid + Liquid -> Solid is cloudy
  • Liquid + Solid -> Gas OR Liquid + Liquid -> Gas is bubbles / fizzing or a loss of mass
• Covalent bonding leads to the formation of substances with different types of structures, for example

  • Small molecules, which contain a fixed number of atoms joined by covalent bonds
  • Giant covalent substances which contain many atoms joined by covalent bonds
• Diamond and graphite

  • Diamond
  • Each carbon atom is joined to four other carbon atoms by strong covalent bonds
  • There are no free electrons
  • Graphite
  • Each carbon atom forms three covalent bonds with other carbon atoms
  • The carbon atoms form layers of hexagonal rings
  • There are no covalent bonds between the layers
  • There is one delocalised electron from each atom
• Properties and uses of Diamond

  Diamond:

  • Diamond is very hard (due to the rigid of carbon atoms held together by strong covalent bonds)
  • Makes it useful for cutting tools
  • Diamond has a very high melting point
  • Does not conduct electricity (no delocalised electrons)
• Properties and Uses of Graphite

  Graphite

  • Has delocalised electrons which can move between the layers in graphite so it can conduct electricity
  • Makes graphite useful for electrodes in batteries and for electrolysis
  • The forces between the the layers are weak. This means the layers can slide over each other - making graphite slippery
  • Useful as lubricant
• Graphene:

  • A single layer of graphite
  • The strong covalent bonds between the carbon atoms mean that graphene
  • Has a very high melting point
  • Is very strong
  • Conducts electricity since it has delocalised electrons that are free to move across its surface
• Fullerenes

  • Molecules of carbon atoms with hollow shapes
  • Structures are based on hexagonal rings of carbon atoms joined by covalent bonds
  • Two examples of fullerenes are buckminsterfullerene and nanotubes
• Buckminsterfullerene:

  • The first fullerene to be discovered
  • Molecules are made up of 60 carbon atoms joined together by strong covalent bonds
  • Molecules are spherical
  • Weak intermolecular forces
  • Need little energy to overcome - slippery and low melting point
• Nanotubes

  • Like a layer of graphene rolled into a cylinder
  • Length of nanotube is very long compared to its width
  • Have high tensile strength - strong in tension and resist being stretched
  • Nanotubes are strong and conduct electricity because they have delocalised electrons
  • Make nanotubes useful for nanotechnology, electronics and specialised materials
• Reactivity Series:

  A) Potassium

  B) Sodium

  C) Lithium

  D) Calcium

  E) Magnesium

  F) Aluminium

  G) Carbon

  H) Zinc

  I) Iron

  J) Hydrogen

  K) Copper

  L) Silver

  M) Gold

  
• When acids react with metals, the products are a salt and hydrogen gas

  Acid + Metal -> Salt + Hydrogen
• Explaining the reactions of acids with metals:

  • The reactions of acids with metals are redox reactions (oxidisation and reduction at the same time)
  • The ionic reaction of magnesium with hydrochloric acid is:
  • 2H+(aq) + Mg(s) → Mg2+(aq) + H2(g)
  • This ionic equation can be split into two half equations:
  • Mg(s) → Mg2+(aq) + 2e-
  • 2H+(aq) + 2e- → H2(g)
• The Neutralisation equation is H+(aq) + OH-(aq) → H2O(l)
• Test for Hydrogen:

  Place a lighted splint in a test tube containing the gas. If the gas is hydrogen, there will be a squeaky pop.
• Test for Oxygen:

  Use a glowing splint, hold it at the end of the tube. If the glowing splint relights, the test tube contains oxygen.
• Testing for Chlorine:

  Make some litmus paper damp and if chlorine gas is present then the litmus paper will be bleached and turn white