chem

• States of Matter are the different forms in which matter can exist
• The three states of matter

  • Solid
  • Liquid
  • Gas
• Solids


  • Have a definite shape
  • Have a fixed volume
  • Particles can vibrate about their fixed positions
  • Particles are arranged regularly in a lattice
• Liquids

  • Take the shape of their container
  • Have a fixed volume
  • Particles can move past one another
  • Particles are randomly arranged
• Gases


  • Take the shape of their container
  • Have no fixed volume
  • Particles are mobile and move randomly
  • Particles are randomly arranged
• Boiling and Evaporation are both endothermic processes
• Boiling


  • Happens at a set temperature called the boiling point
  • Occurs throughout the liquid
  • A relatively faster process
• Evaporation


  • Occurs at any temperature below the boiling point and above the freezing point (liquid)
  • Only occurs at the surface
  • A slow process
• Condensation


  • The process by which a gas converts into a liquid
  • Happens at the same temperature as the boiling point
• Melting


  • The process in which a solid converts to a liquid
  • Happens at a set temperature called the melting point
• Freezing


  • The process in which a liquid converts to a solid
  • Happens at the same temperature as the freezing point
• Sublimation


  Occurs when a solid has enough energy to convert into a gas or gas converted into a solid
• Cooling Curve


  1. Particles of gas move slower and slower and the gas contracts

  2. Particles get closer together and intermolecular bonds start to form at condensation point

  3. Temperature stops falling as energy released by bond formation cancels out energy lost due to cooling

  4. Temperature starts falling again once all gas has turned to liquid and liquid begins to contract until freezing point

  5. At freezing point, intermolecular bonds between liquid molecules start to develop to form a solid
• Heating Curve


  1. Particles of solid start to vibrate faster and faster and the solid begins to expand

  2. At melting point, intermolecular bonds between particles begin to break

  3. Temperature remains constant until all solid has turned to liquid as energy received is cancelled by energy used to break bonds

  4. Once all solid has turned to liquid, temperature starts to rise again and liquid begins to expand until boiling point

  5. At boiling point, intermolecular bonds between liquid molecules start to break down to form a gas

  
• Diffusion


  The net movement of particles from a region of higher concentration to a region of lower concentration as a result of their random movement until equilibrium is reached
• The rate of diffusion is most rapid in gases > liquids > solids
• Effect of Relative Molecular Mass in Diffusion

  Molecules with a lower mass move faster on average than those with a higher mass at the same temperature
• Increase in external pressure

  Produces a contraction (decrease) in volume. The gas is said to be compressed.

  
• Fall in external pressure

  Produces an expansion (increase) in volume. The gas is said to be decompressed.

  
• Increase in temperature


  Increases the kinetic energy of gas molecules, causing them to hit the walls of their container more often and with greater force, increasing internal pressure and volume

  
• Decrease in temperature


  Decreases the kinetic energy of gas molecules, causing them to hit the walls of their container less often and with less force, decreasing internal pressure and volume
• Elements


  A substance made of atoms that share the same number of protons and cannot be broken down into simpler substances by chemical methods
• Compounds


  Two or more elements chemically bonded together (in a fixed proportion)
• Mixtures


  Two or more elements not chemically bonded together
• Atom


  • Central nucleus containing neutrons and protons surrounded by electrons in shells
  • Protons have a relative mass of 1 and a relative charge of +1
  • Neutrons have a relative mass of 1 and a relative charge of 0
  • Electrons have a relative mass of 1/1840 and a relative charge of -1
• Proton Number (Atomic Number)


  The number of protons in the nucleus of an atom, unique to each element
• Nucleon Number (Mass Number)

  The total number of protons and neutrons in the nucleus of an atom
• Electronic Configurations


  • Electrons orbit the nucleus in shells, with the first shell having a max capacity of 2 electrons and subsequent shells holding up to 8
  • Group VIII noble gases have a full outer shell
  • The number of outer shell electrons equals the group number in Groups I to VII
  • The number of occupied electron shells equals the period number
• Isotopes


  Different atoms of the same element with the same number of protons but different numbers of neutrons
• Relative Atomic Mass


  The mass of an element relative to the mass of carbon-12, calculated using the abundance of naturally occurring isotopes

  
• Metallic Bonding


  • The electrostatic attraction between positive ions in a giant metallic lattice and a "sea" of delocalised electrons
  • Gives metals good electrical conductivity, high melting and boiling points, malleability, and ductility
• Diamond


  • Each carbon atom is joined with four other carbon atoms
  • High melting and boiling points due to strong covalent bonds
  • No delocalised/free moving electrons
  • Cannot be scratched easily
  • Transparent
  • Cannot conduct electricity
  • Hard structure
  • Giant lattice arrangement
  • Used for cutting tools
• Graphite


  • Each carbon atom is joined with three other carbon atoms
  • High melting and boiling points due to strong covalent bonds within layers, but layers are attracted by weak intermolecular forces
  • Contains delocalised/free moving electrons
  • Can be scratched easily
  • Opaque/black
  • Can conduct electricity
  • Soft, with layers that can slide easily
  • Used as a lubricant and electrode in electrolysis
• Silicon (IV) Oxide


  • Similar structure to diamond
  • Hard structure
  • High melting and boiling point
  • Rigid tetrahedral structure
  • Does not conduct electricity
• Covalent Bond


  Pairs of electrons shared between two atoms leading to noble gas electronic configuration (2.8.8)
• Different Types of Covalent Bonds

  • Single Bonds
  • Double Bonds
  • Triple Bonds
• Properties of Covalent Compounds

  • Intermolecular forces are weak but covalent bonds are strong
  • Have low melting and boiling points, requiring less energy to overcome intermolecular forces
• Silicon Dioxide (SiO2)


  • High melting and boiling point - More energy to overcome
  • Rigid Tetrahedral Structure
  • Does not conduct electricity
• Each Silicon atom is covalently bonded with 4 Oxygen Atoms
• Each Oxygen atom is covalently bonded with 2 Silicon Atoms