IGCSE Organic Chemistry: Key Concepts Explained

Alkanes are hydrocarbons with only single bonds between carbon atoms. Let's examine methane, the simplest alkane.Ethane has two carbon atoms connected by a single bond, with three hydrogens attached to each carbon.Propane contains three carbon atoms in a chain, with eight hydrogen atoms.These alkanes form a homologous series, where each member differs by one CH₂ group. The general formula is C n H two n plus two.Let's examine how properties change across the series. Notice how boiling points increase as the number of carbon atoms increases.As we add more CH₂ groups, we see a clear trend: boiling points increase, and physical states change from gases to liquids.Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond. Let's examine ethene, the simplest alkene.The double bond consists of four shared electrons between the carbon atoms, making alkenes more reactive than alkanes.When bromine is added to ethene, it undergoes an addition reaction, breaking the double bond.The product is 1,2-dibromoethane, where each bromine atom attaches to a carbon.This addition reaction follows a specific mechanism. First, the bromine molecule approaches the electron-rich double bond.Then, the double bond breaks, and new single bonds form with the bromine atoms.We can test for the presence of a double bond using bromine water. The orange-brown color of bromine disappears when it reacts with an alkene.Alcohols are organic compounds containing the hydroxyl group, OH. Let's examine ethanol as an example.Alcohols have unique properties due to their OH group.Now let's examine carboxylic acids, which contain the COOH group. Here's acetic acid, a common example.The COOH group gives carboxylic acids their acidic properties.Carboxylic acids have several distinctive properties.On the pH scale, carboxylic acids typically have values between 3 and 5, making them weak acids.Polymers are large molecules made up of many repeating units called monomers.Through a process called polymerization, many ethene molecules join together to form polyethene.During polymerization, the double bond in ethene breaks, allowing many molecules to link together in a chain.Polymers have numerous applications in our daily lives.They are used extensively in packaging, construction, and electronics.However, the widespread use of polymers has significant environmental impacts.Plastics are non-biodegradable and can persist in the environment for hundreds of years, leading to serious pollution problems.To address these challenges, we need to focus on solutions like recycling, using biodegradable alternatives, and reducing our overall plastic consumption.Let's review what we've learned about polymers and their impact on our world.Remember that while polymers are incredibly useful materials, we must be mindful of their environmental impact and work towards sustainable solutions.Thank you for learning about polymers and their applications with Spark.E!