paper 2 chemistry

• The rate of a reaction is the change in a quantity divided by time, which can be the quantity of reactant used or product formed, usually measured as mass or volume of gas
• An experiment to measure reaction rate could involve reacting hydrochloric acid and sodium thiosulfate in a conical flask over a cross on paper, stopping the timer when the cross is no longer visible due to increased turbidity
• Another experiment could measure the volume of gas produced using a gas syringe, with a graph showing quantity on the y-axis and time on the x-axis, typically starting steeply and then leveling out to indicate completion
• Factors that increase the rate of a reaction include increasing reactant concentration, gas pressure, surface area of solid reactants, and temperature, with a catalyst reducing the activation energy needed for successful collisions
• Reversible reactions can return to their original reactants after forming products, like the Haber process where hydrogen and nitrogen make ammonia, which can also break down back into separate gases
• Le Chatelier's principle states that if a system at equilibrium is changed, the system will adjust to counteract that change, such as increasing pressure favoring the forward reaction in a reaction with more moles on the left side
• Increasing temperature favors the endothermic reaction, while decreasing pressure or concentration shifts the equilibrium position to favor the side with fewer molecules, and removing heat favors the exothermic reaction
• Organic compounds have carbon as the backbone, with crude oil mainly consisting of hydrocarbons, specifically alkanes which are chains of single covalently bonded carbon atoms surrounded by hydrogen atoms
• Fractional distillation separates crude oil into different length alkanes based on boiling points, with longer alkanes having higher boiling points and being more viscous, while shorter alkanes are more flammable and used for fuel
• Polymers used for plastics can be made from alkenes, which have a carbon-carbon double bond making them unsaturated, unlike alkanes which are saturated, and can be tested by adding bromine water to see if the color disappears
• Alkanes are already saturated and cannot undergo saturation like alkenes
• Chlorine and iodine react similarly in their saturation process
• Water can saturate an alkene by attaching itself as an H and an O functional group, forming an alcohol
• Cracking is a process that breaks apart longer alkanes into shorter alkanes and alkenes to meet the demand for shorter alkanes and produce alkenes for other materials
• Catalytic cracking requires a temperature of around 550°C and a catalyst called a zeolite
• Steam cracking, another form of cracking, uses an even higher temperature of over 800°C in the absence of a catalyst
• Cracking of butane can produce ethane and ethene, which can further be used for making polymers
• Polymers are super long-chain alkanes made up of repeating sections called monomers
• Polymerization can occur through addition polymerization or condensation polymerization
• Amino acids are the building blocks of proteins, polymerized to form polypeptides
• DNA, deoxyribonucleic acid, stores genetic code and is made from nucleotides
• Starch and cellulose are natural polymers made from glucose
• Chemical analysis methods include testing melting and boiling points, chromatography, flame tests for metals, and chemical tests for specific ions
• Instrumental methods in chemistry labs are used for accurate and fast substance identification
• Atmospheric chemistry has changed over Earth's history, with gases like nitrogen, carbon dioxide, and methane playing crucial roles in the Earth's climate
• Algae and plants reduce carbon dioxide in the atmosphere by turning CO2 into oxygen through photosynthesis, decreasing CO2 levels to 0.018%
• Water vapor, carbon dioxide, and methane absorb longer wavelength radiation, keeping the Earth warm; without them, we would freeze - this is the greenhouse effect
• CO2 levels have increased since the Industrial Revolution, contributing to global warming, although it's only responsible for a small percentage of the greenhouse effect compared to water vapor, which accounts for 95%
• Carbon monoxide is an atmospheric pollutant that binds to red blood cells, reducing oxygen transport and can be fatal; fossil fuels release sulfur dioxide causing acid rain, nitrogen oxides leading to breathing problems, and particulates of carbon from incomplete combustion causing health issues
• Sustainability involves using resources for warmth, shelter, food, and transport without compromising future generations' abilities to do the same
• Potable water is safe to drink, obtained from freshwater sources with low salt levels, treated to remove particles, sterilized to kill microbes, and sometimes desalinated from seawater
• Extracting metals from the earth involves mining ores and using processes like reduction or displacement reactions; new methods like phytomining and bioleaching are being developed for copper extraction
• Life Cycle Assessment (LCA) predicts a new product's environmental impact by considering extraction, processing, manufacturing, use, disposal, and transportation stages; reducing product use, materials, energy, and recycling can lessen environmental impact
• Corrosion is the gradual destruction of materials by chemical reactions; metals can be coated with a more reactive metal to prevent corrosion, alloys like stainless steel are resistant to corrosion, and composites are materials made from two different materials
• Polymers can be thermosoftening or thermosetting, with thermosetting polymers forming cross-links between polymer chains, making them not melt when heated
• The Haber process produces ammonia from nitrogen and hydrogen, essential for fertilizers, by passing the gases over a catalyst at high pressure and temperature
• Flame test to identify metal ions

  1. Place small amount of chemical on wire

  2. Place wire in blue Bunsen burner flame

  3. Observe color of flame
• Metal ions identified by flame test

  • Lithium (crimson flame)
  • Sodium (yellow flame)
  • Potassium (lilac flame)
  • Calcium (orange-red flame)
  • Copper (green flame)
• Flame test color can be difficult to distinguish, especially with low concentrations or mixtures of metal ions
• Flame emission spectroscopy


  Technique where metal ion in solution is placed in flame, light given out is passed into a spectroscope which converts it into a line spectrum