CHEMISTRY

Hello! This is my own notes that I made after collating all my errors across all the papers I have done. It touches on content and keywords. I won’t guarantee that the notes are 100% accurate and will give you a distinction but I spent a lot of time and effort on them and it helped me a lot so I wanna share them with y’all! Some wordings might be confusing to understand I’m sorry 😔 Amount of… : moles % yield not 100 - impurities present in sample, may dissolve back to solution, smt else formed Catalyst in process - reactant in first stage and pro use in last stage When saying ph state whether acidic basic or neutral too Try to explain in terms of mol When comparing experiments, just say experiment … and … 1 mol HCL same mol as 0.5 mol h2so4 - collects twice the product for same conc (only conc changes) Change to g when doing mol ratio Macromolecule: v large molecule made up of many repeating units of monomers covalently bonded tgt. Condensation polymerisation: monomers w 2 functional grp react and results in loss of molecules such as water molecules. Addition polymerisation: chemical reaction where unsaturated monomers alkenes join tgt by breaking cc double bonds, w/o losing any molecules Silicon dioxide is an acidic oxide but has ph7. Only show that it’s acidic oxide when it reacts w base. It’s insoluble in water. Hydrogen peroxide is a bleach so solution turns colourless ✨ conserve!! Rate of reaction at… -> draw tangent at that point Pressure only affects gasssss Stopwatch is just a square Ammonia formed is condensed and obtained as a liquid Decomposition of hydrogen peroxide: 2h2O2 —> 2h2O + O2 Ppt just say insoluble too Experimental chem ● Styrofoam - reduce heat loss to surroundings (temp change will be more accurate) ● Cannot measure hydrogen gas using balance (and some other gases, see Mr, as they are v light) ● Burette can be used for water displacement but not ideal as it limits how much gas can collect

● See vol of gas going to be produced and which apparatus can measure that vol ● Chromatography dosent show all substances present in the mixture ● Iodine can be sublimed ● Sodium chloride (most sodium salt) is always evaporation dryness ● For large scale production, evaporation is done via distillation flask ● Solid mixture (have soluble and insoluble solid), add water then heat! To dissolve the soluble solid then filter ● Min number of apparatus qn… just red litmus enough if there’s chlorine but need both red and blue for acidic and alkali alone ● Consider solubility ● Gas (lower density) cannot be easily collected back but solid can to be recycled. Transported in liquid state as take up less space for easy handling ● Chlorine, ammonia (very) and oxygen is soluble in water, hydrogen is not. ● Cotton wool plug is used to prevent chemical splash ● Expected results may be more cuz gas dissolve in solution ● Increase decomposition by increasing temp ● How to test if …smt is catalyst? — conduct exp and see if mass of catalyst remained same ● Metals cleaned w sandpaper first to remove any oxide layer (for better electrical conductivity) Diffusion - particles of perfume move from region of higher concentration to region of lower concentration until there is no net movement / no overall change in concentration - Gain Kinetic energy allows particles to move faster and further Atomic structure ● Graphite is a lubricant (soft and slippery) - IMFOA between layers ● Alloy conducts electricity but not as well as pure metal. Elements of alloys (mixture) are not chemically combined and there’s no mobile electrons. ● Alloys are hard because LAYERS of atoms cannot slide over eo easily when force is applied ● When an element burns in excess o2, substance formed is always greater in mass than the element (Mg—> MgO) ● Metallic bonding -> strong electrostatic forces of attraction between positive metal ions and sea of delocalised e ● Ethanol add to water - vol decreases cuz ethanol molecules move into empty spaces between water molecules (50cm cube + 50 cm cube not = 100cm cube) ● Hydrogen don’t have neutrons omg ! ● Gases w same vol have same no of moles as molar volume is 24dm cube. But have diff masses as they have diff Mr ● The element in compound is the one reduced/oxidised ● Superoxide ion has only 7 valence electrons for one oxygen atom

● Don’t put Roman numerals in chemical formula ● Hydrogen can gain lose share electrons Chemical bonding ● In giant lattice, 1 sodium ion surrounded by 6 chloride ions ● Solutions of ionic compounds (electrolysis of molten) are broken down into constituent elements while there is no change to metals when electricity is passed through . ● NaOH is a white solid w high melting point (ionic compound) that dissolves in water to form an alkaline solution (ionises in water to produce OH- ions) ● Not all ionic compounds are soluble in water (BaSO4..) ● take electrons from another ELEMENT (not atom) ● Ammonia is a simple molecular substance ● Say what is what diamond is giant covalent structure bonded by strong covalent bond ● Crystalline product- solid ● Water has very few mobile electrons or ions - poor electrical conductors ● When talk abt elements compound mixture, Rmb ratio, chemically combined ● Carbon added to iron to increase its hardness and strength. But when too much added, steel become brittle. Too less, steel become too soft. ● Simple molecular structure: small discrete molecules held tgt by WIMFOA ● Giant covalent structure: atoms held tgt by strong covalent bonds throughout structure. ● Alloy does not conduct electricity as well as pure metal as diff sized atoms in alloy disrupts orderly arrangement of metal lattice. Free moving electrons cannot move along layers easily. ● State what the mobile charge carriers are (ions/electrons) ● When excess … added, can now conduct electricity as .. unreacted and act as mobile charge carriers ● Molecule present during reaction may be water molecules ● Not all metals have high melting points ● As metal become bigger in atomic size, metallic bonds become weaker ● Oxygen produced can react w graphite to form Co2 ● Oxygen exist as a diatomic molecule always Acids and bases (try to say alkali) ● Ph give a measure of H+ conc in solutions - electrolyte ph decrease cuz of h+ ● When acids react w metals, hydrogen ions gain e (acid metal reaction is redox) ● Reactive metal displaces hydrogen from acid (metal acid reaction) ● Hydroxide ion acts as a base to remove hydrogen ions from ammonium ion ● End point of titration is the middle of the straight line ● Ammonia plus acid gives ammonium sal