Chemistry - End of Year

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gold leaf Most went straight through and some were deflected Showed that the atom was mostly empty-space Central positive nucleus which repelled the positively charged alpha particles Same charges repel each others Electron Shells: N. Bohr Realised that electrons orbit the nucleus in discrete shells Each shell has a set amount of energy Mass Discrepancy: J. Chadwick Measured mass of atom Discovered discrepancies in measurements Found out about neutron Non-charged particle CHEMICAL BONDING: ☐☐ Ionic Bonding: Metal + Non-metal Metal loses electrons and nonmetal gains electrons until both have a full outer shell Electrostatic forces between oppositely charged ions which requires lots of energy to break, which is why they have high melting points Can only conduct electricity when molten or aqueous as the ions become free to move Diagram: Symbol Charge Square brackets Dots and crosses diagram Metallic Bonding: Metal + Metal Can conduct electricity due to sea of delocalised electrons High melting point Malleable as the layers can slide over each other Alloys: Made by mixing 2 or more metals together Not malleable as the layers are distorted and can't slide over each other Giant Covalent Structures: Non-Metal + Non-Metal Strong covalent bonds which require lots of energy to break so high melting point Not malleable as the layers can't slide over each other (graphite is the only exception) Can conduct electricity due to the delocalised electrons (diamond is the only exception) Simple Covalent Molecules: Non-Metal + Non-Metal Simple molecules Weak intermolecular forces between layers which require little energy to overcome so lower boiling points ORGANIC CHEMISTRY: KEY TERMS: Saturated: HYDROCARBONS: Alkanes: All carbon atoms are bonded with single covalent bonds Saturated Homologous series General formula: CnH₂n+2 Alkenes: Homologous series Unsaturated Has one double bond between carbon atoms General formula: CnH₂n Alcohols: Has an oxide molecule instead of hydrogen General Formula: CnH₂n+1OH Cracking: When a large alkane molecule is broken down into: Smaller alkane Alkene Thermal Decomposition reaction Not enough hydrogen atoms to make two alkanes Smaller alkanes are more flammable / volatile Lower Melting / Boiling point Less energy to heat Produce more energy when burned More efficient ATMOSPHERIC POLLUTANTS: Incomplete Combustion: Not enough oxygen to make a complete combustion Not as efficient Produces less energy Produces carbon monoxide Produces soot Causes global dimming Soot covers up sun Sulphur Oxides: Reacts with air to form sulfuric acid Causes acid rain Corrosive rain that can destroy crops and buildings Nitrogen Oxides: Reacts with air to form nitric acid Harmful to the environment FRACTIONAL DISTILLATION: The process of separating crude oil into different hydrocarbons Crude oil: Mixture of hydrocarbons with different boiling points Process: Heat the crude oil to a very high temperature All of the compounds are evaporated from liquid to gas Hot gaseous hydrocarbons then rise up the fractionating column ☐ Hot gas rises As they rise, they cool down Top of the column is cooler than the bottom. Hydrocarbons will condense when they become cooler than their boiling point Liquid hydrocarbons then collect in trays and drain out Longer chain hydrocarbons condense at the bottom of the fractionating column Have high boiling points. Shorter chain hydrocarbons condense at the top of the column Much lower boiling points. CALORIMETRY: ☐ Thermal Energy = Mass x Specific Heat Capacity x Change in Temperature Specific heat capacity is how easy it is to heat something up All variables applies to object being heated