Chemistry paper 2

• Rate of reaction is the speed at which a reaction happens, calculated as the change in quantity divided by time
• Quantity can be the reactant used or product formed, measured in mass or volume of gas
• Mean rate is used as the rate could be changing over time
• Experiment example: Reacting hydrochloric acid and sodium thiosulfate to measure rate
• Another experiment: Measuring volume of gas produced using a gas syringe
• Factors that increase rate of reaction:

  • Increasing concentration of reactants in solution
  • Increasing pressure of gas reactants
  • Increasing surface area of solid reactants (crushing into a powder)
  • Increasing temperature, particles move more quickly and collide with more energy
• Adding a catalyst increases rate by reducing activation energy needed
• Reversible reactions can go back to original reactants, e.g., Haber process
• Le Chatelier's Principle: If a system at equilibrium is changed, it will adjust to counteract that change
• Changing pressure or concentration affects equilibrium position
• Increasing temperature favors endothermic reaction, higher energy input
• Endothermic reactions require energy input, exothermic reactions release energy
• • Testing for alkenes: Add bromine water, turns colorless if alkene present
  • Cracking breaks longer alkanes into shorter alkanes and alkenes
  • Catalytic cracking uses a catalyst and lower temperature, steam cracking uses high temperature
  • Polymers are long-chain molecules made from repeating monomers
  • Polyethene is an example of a polymer made from ethene monomers
• Organic Chemistry:

  • Organic compounds have carbon forming the backbone of molecules
  • Crude oil consists mostly of hydrocarbons (carbon and hydrogen atoms)
  • Alkanes are chains of single covalently bonded carbon atoms with hydrogen atoms
  • General formula for alkanes: CNH2N+2
  • Fractional distillation separates crude oil into different length alkanes
  • Longer alkanes have higher boiling points due to stronger intermolecular forces
  • Alkanes can be used as fuels through combustion producing carbon dioxide and water
  • Alkenes have a carbon-carbon double bond, unsaturated
• Chemical Analysis:

  • Alcohols have an -OH functional group, names end with -ol
  • Short alcohols can mix with water to form a solution
  • Oxidizing alcohols without combustion produces carboxylic acids
  • Polymers can be made through addition polymerization using monomers with double bonds
  • Condensation polymerization joins monomers with two functional groups, producing water
  • Amino acids are building blocks of proteins, have amino and carboxy groups
  • Amino acids can be polymerized to form polypeptides
  • DNA stores genetic code, made from nucleotides
• • Starch is a natural polymer made from repeating glucose units
• DNA is made from two polymers that spiral around each other in a double helix
• DNA is made from four different monomers called nucleotides
• Starch is a natural polymer with glucose as the monomer
• Cellulose is a polymer made from beta glucose
• Proteins have amino acids as their monomers
• Testing for purity in chemistry involves checking the melting point or boiling point of a substance
• Formulations are mixtures designed for specific purposes with specific quantities of substances
• Chromatography is used to separate substances in mixtures
• Chromatography involves a stationary phase (e.g., chromatography paper) and a mobile phase (e.g., water)
• Chemical tests for gases include:

  • Hydrogen: produces a squeaky pop with a burning splint
  • Oxygen: relights a glowing splint
  • Carbon dioxide: turns lime water cloudy
  • Chlorine gas: bleaches damp blue litmus paper
• Flame tests for metals:

  • Lithium: crimson flame
  • Sodium: yellow flame
  • Potassium: lilac flame
  • Calcium: orange-red flame
  • Copper: green flame
• Testing for metals in solutions with sodium hydroxide:

  • Aluminium, calcium, and magnesium produce a white precipitate
  • Copper 2+ ions form a blue precipitate
  • Ion 2 forms a green precipitate
  • Ion 3 forms a brown precipitate
• Carbonates react with acids to produce carbon dioxide gas
• Testing for halide ions with silver nitrate solution and nitric acid:

  • Chlorine ions form silver chloride (white precipitate)
  • Bromine ions form silver bromide (cream precipitate)
  • Iodine ions form silver iodide (yellow precipitate)
• Sulfate ions produce a white precipitate when mixed with barium chloride and hydrochloric acid
• Instrumental methods are used in labs for accurate and fast substance determination
• Flame emission spectroscopy is used to identify metal ions by analyzing emitted light wavelengths
• Atmospheric chemistry involves the composition of gases in the atmosphere
• The greenhouse effect is caused by gases like water vapor, carbon dioxide, and methane absorbing longer wavelength radiation
• Increased carbon dioxide levels since the industrial revolution may contribute to global warming
• Carbon monoxide is an atmospheric pollutant that binds to red blood cells and can be fatal
• Fossil fuels release sulfur dioxide, nitrogen oxides, and carbon particulates, which can cause health issues
• Resources are used for warmth, shelter, food, and transport
• Sustainability involves using resources without compromising future generations' abilities to do the same