Chemistry: Section A

Chapter One: Kinetic Theory and Diffusion
1. Heating a substance makes its particles vibrate faster
2. Changes of state
  1. Heating up a solid so that its particles vibrate so fast that it becomes a liquid is known as melting
  2. Heating up a liquid so that its particles vibrate so fast that it becomes a gas is known as boiling
  3. Cooling down a gas so that its particles vibrate so slow that it becomes a liquid is known as condensing
  4. Cooling down a liquid so that its particles move so slow that it becomes a solid is known as freezing
  5. Heating up a solid so that its particles vibrate so fast that it becomes a gas is known as subliming
  6. Evaporation is when the surface of a liquid comes into contact with the air and is released into the air becoming a gas. This requires no external heating, making it different to boiling
3. Diffusion
  1. Diffusion is a natural process that occurs when the natural movement of particles in liquids and gases causes them to mix around.
  2. Diffusion in liquids is slower than in gases because there are less gaps for particles to move and mix into
Chapter Two:Atomic Structure
1. Electrons
  1. Relative Mass: 1/1836
  2. Relative charge: -1
2. Protons
  1. Relative Mass: 1
  2. Relative Charge: -1
3. Neutrons
  1. Relative Mass: 1
  2. Relative Charge: 0
4. Isotopes
  1. A variant of an element with a different number of neutrons
  2. Atomic number is not affected
  3. Mass number is different
  4. No chemical properties are changed as these are dictated by electron and proton number
  5. Only difference is weight
5. Atomic number is the number of protons in an atom
6. Mass number is the number of protons plus the number neutrons in an atom
7. Electrons are found in shells at different energy levels orbiting the atom's nucleus
8. Protons and neutrons are found in the core or nucleus of an atom
Chapter Three: Bonding
1. Covalent
  1. Occurs between two non-metals
  2. Involves two atoms sharing the electrons in their outer shells so that they both have a full outer shell
2. Ionic
  1. Occurs between a metal and a non-metal
  2. Involves a metal atom giving its outer shell electrons to a non-metal atom so that they both have full outer shells
  3. The metal becomes a positively charged ion, a cation
  4. The non-metal becomes a negatively charged ion, an anion
  5. The anion and the cation are attracted to each other and therefore bond
3. Metallic
  1. Occurs between two metals
  2. Metal ions shed their outer shell of electrons, becoming positively charged and now attracted to the negatively charged delocalised 'sea' of electrons between them
  3. Delocalised 'sea' of electrons allows flow of electric current (movement of electrons)
  4. These are extremely strong because they involve completely removing an outer shell of electrons
  5. The more electrons that are delocalised, the stronger the bond
4. Intermolecular
  1. Occurs within substances
  2. Caused by the electrostatic attraction between molecules
  3. These bonds are broken when substances change state
Chapter Four: Structure
1. Metallic
  1. Seen in metals because of (see) metallic bonding
  2. Positively charged metal ions and a delocalised 'sea' of electrons
  3. High melting points to due the attraction forces that need to be overcome
  4. Conductive of heat and electricity due to 'sea' of electrons
  5. Workable as layers can slide over and around each other
2. Giant Ionic
  1. A lattice of anions and cations formed by (see) ionic bonding
  2. Crystalline due to regular arrangement of lattice
  3. Brittle as layers cannot slide over each other as ion size is irregular
  4. High melting points due to strong forced holding lattice together
  5. Generally soluble in water
3. Giant Covalent
  1. Caused by (see) covalent bonding
  2. Structure of many covalent bonds
  3. Do not conduct electricity as there are no free electrons to move
  4. Generally insoluble in water
  5. Durable due to strong bonds
  6. High melting points due to strong bonds
4. Molecular
  1. Low melting points as intermolecular forces are weak
  2. Generally insoluble in water without a reaction
  3. Generally soluble in organic solvents
  4. Do not conduct electricity as there are no free elctrons
Chapter Five: Formulae and Equations
1. Formulae for ionic compounds
  1. Valency is the charge that an atom would have when turned into a cation or an anion
  2. The valency of total cations must equal the valency of total anions
  3. If a cation has valency 2, and the anion has valency 1, then two anions will bond with one of the cations, as in LiBr2
2. Formulae for covalent compounds
  1. The formula can be seen from a diagram by counting how many of each element is in the compound
3. State symbols
  1. (s) means solid
  2. (l) means liquid
  3. (g) means gas
  4. (aq) means dissolved in water
Chapter Six: Rates of Reaction
1. Some reactions such as rusting occur over long periods of time
2. Some reactions such as those between acids and bases can occur in seconds or minutes
3. Collision theory
  1. For a reaction to occur, two particles must collide successfully with the required activation energy to react with each other
  2. Increasing temperature means that particles are moving around faster, increasing the likelihood that they collide, increasing the rate of the reaction
  3. Increasing pressure makes the particles closer together, increasing the likelihood that they collide, increasing the rate of the reaction
  4. Increasing the surface area of one of the reactants gives more area in which collisions can take place at once, increasing the number of collisions ad therefore increasing the rate of the reaction
  5. Increasing concentration increases the number of particles in a given volume, increasing the likelihood they they collide, increasing the rate of the reaction
4. Catalysts
  1. Catalysts are substances that provide an alternative reaction route that requires a lower activation energy
  2. This means that more collisions are successful, increasing the rate of the reaction
  3. Catalysts are not used up in the reaction and can be used again and again, making them economically viable in industry

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