Year 9 Chemistry Test 2 Revision List PDF

Year 9 Chemistry Test 2 Revision List ​ Flame Tests for some Cations – I can describe the colour change of metal ions when heated strongly. ○​ Method ​ Dissolve ionic compound in solution ​ Soak wooden splint in solution ​ Burn wooden splint in bunsen burner under...

Year 9 Chemistry Test 2 Revision List ​ Flame Tests for some Cations – I can describe the colour change of metal ions when heated strongly. ○​ Method ​ Dissolve ionic compound in solution ​ Soak wooden splint in solution ​ Burn wooden splint in bunsen burner under a high temperature flame ​ Observe colour of flame ○​ Summary table Metal Cation Colour in Flame Under Blue Cobalt Glass Li+ Pink-Red Same Na+ Yellow White K+ Lilac White Ca2+ Orange-red White Ba2+ Apple green White Cu2+ Green & Blue Cyan/White ​ Silver Precipitate Test for the Halide Anions – I can describe the colour produced by the silver halide precipitate and identify the halide anion by it. ○​ Method ​ Add 1cm3 of the suspected halide solution to a test tube ​ Add a few drops of silver nitrate solution (AgNO3(aq)) and observe the colour of the precipitate (solid coming out of the solution) ○​ Summary table Halide Anion Colour of Silver Halide Precipitate Cl- White Br- Cream I- Yellow ​ Using Ammonia Precipitates to Identify Metal Ions – I can tell which solution something is based on the ammonia precipitates. ○​ Method ​ Take 2cm3 of each metal salt solution  ​ Add drops of Ammonia solution (NH3(aq)) ​ Shake ​ Record colour and appearance of precipitate ​ Add an excess for solubility test ○​ Summary table ○​ Aluminium and zinc are similar; zinc is if it’s soluble, and aluminium if it’s not. Solution Precipitate Appearance Soluble? ZnSO4 Milky white, cloudy, YES grainy CuSO4 Opaque, blue, grainy YES CaCl2 Transparent, clear, YES grainy FeSO4 Grey-green, fine NO, turned dark green FeCl3 Orange-brown, fine, NO grainy Al2(SO4)3 Translucent, cloudy NO Cr2(SO4)3 Dark green-blue, fine NO ​ Using Hydroxide Precipitates to Identify Metal Ions – I can recall how to do this experiment. ○​ Other metals have insoluble hydroxide compounds ​ To identify, use sodium hydroxide solution in a solution of a metal salt ​ If precipitate is formed, then it must be the metal hydroxide ○​ Method ​ Take 1cm3 of metal salt solution and add drops of NaOH(aq) ​ Shake ​ Add ½ a test tube’s worth of NaOH(aq) for solubility testing ○​ Summary Table Solution Precipitate Soluble? Formula for (OH-) Appearance precipitate ZnSO4 White and YES Zn(OH)2 Zn2+ quite gelatinous, cloudy CuSO4 Blue and NO Cu(OH)2 Cu2+ gelatinous  CaCl2 Liquid, white, NO Ca(OH)2 Ca2+ cloudy, grainy FeSO4 Grainy and NO Fe(OH)2 Fe2+ dark green FeCl3 Reddish-brow NO Fe(OH)3 Fe3+ n, slightly gelatinous and grainy Al2(SO4)3 Partly cloudy, YES Al(OH)3 Al3+ clear, gelatinous Cr2(SO4)3 Emerald, YES Cr(OH)3 Cr3+ liquidy, grainy, gelatinous ○​ All form insoluble hydroxides? ​ No; zinc, aluminium, and chromium are soluble hydroxides ○​ After a bit, what happens to the iron(II) hydroxide’s precipitate? ​ Some red particles are on the side of the test tube ○​ Which precipitates do not last but redissolve when an excess of NaOH(aq) is added? ​ Aluminium precipitates ○​ Why use two chemicals to test these two ions? ​ Identify similar ions ​ Ex. Copper is soluble in ammonia excess while Cr3+ and Fe2+ are both green and aren’t soluble in ammonia excess while Cr3+ is in sodium hydroxide ​ Able to differentiate between chemicals by adding excess ​ Covalent Bonding – I can describe what covalent bonding is and draw dot and cross diagrams for them. ○​ The attraction of the shared pair of electrons to the positive nucleus of the 2 atoms ○​ Neither atom has a particularly stronger attraction than the other ​ No transfer of electrons ○​ SHARE ELECTRONS!!! ○​ How to name a covalent compound ​ Write name of first non-metal in the chemical formula ​ Write the other name of the other non-metal with an “ide” at the end. Add number prefixes to indicate the number of atoms  ○​ When drawing covalent diagrams for atoms, we ONLY include the electrons in the outer orbit. ○​ Formation of Hydrogen Fluoride molecule ​ H: 1 ​ F: 2.7 (Needs one to attain full outer orbit) ​ Hydrogen shares its 1 so both have a full outer shell ​ Single bond: 1 x, 1 o ○​ Formation of Chlorine molecule ​ Cl: 2.8.7 ​ Two are needed, each atom shares one electron ​ Single bond: 1 x, 1 o ​ Cl — Cl ○​ Formation of Oxygen molecule ​ O: 2.6 ​ Four are needed, each atom shares two electrons ​ Double bond, 2 x, 2 o ​ O = O ○​ Formation of Nitrogen molecule ​ N: 2.5 ​ Six are needed, each atom shares three electrons ​ Triple bond, 3 x, 3 o ​ N ≡ N ○​ Formation of Carbon Dioxide molecule ​ CO2 ​ C: 2.4 ​ O: 2.6 ​ 4x2 are needed, each atom shares two electrons x2 ​ Double bond x2, 2 x, 2 o ​ O = C = O ○​ Formation of Methane molecule ​ CH4 ​ C: 2.4 ​ H: 1 ​ 2x4 are needed, each atom shares one electron x4 ​ Single bond x4, 1 x, 1 o ​ ​ ​ H ​ ​ ​ | ​ H – C – H ​ ​ ​ | ​ ​ ​ H  ○​ The maximum number of bonds that can form between two atoms is three bonds (N ≡ N) ○​ The maximum number of bonds that an atom can form with other atoms is 4 bonds (CH4) ​ Ionic vs Covalent – I can identify the differences between ionic and covalent bonds. ○​ Table​ Property Ionic Compounds Covalent Compounds Type of Metal and nonmetal Nonmetals only elements Bonding Ionic - attraction between Covalent - sharing of pair(s) anions and cations of electrons between atoms Representative Formula unit Molecule unit What the The ratio of cations to The type and number of formula anions atoms in the molecule represents Physical state at Solid Gas, liquid, solid room temperature Water solubility Usually high Variable Melting and Generally high Generally low boiling temperatures Electrical Good when molten or in Poor conductivity solution State when Separates into ions Remains molecules dissolved in water ​ Tests for Molecules – I can remember several molecule tests and their results. ○​ Testing for carbon dioxide molecules ​ Passing gas through limewater (calcium hydroxide solution) ​ Limewater reacts with carbon dioxide to produce a precipitate of white calcium carbonate ​ Limewater looks milky ○​ Testing for Oxygen molecules  ​ Relies on the fact that if something is burning slowly in the air (21% oxygen), plunging it into 100% oxygen will greatly increase the rate of the burning reaction ​ Light wooden splint on fire ​ Blow it out ​ Splint is glowing ​ Put it in test tube filled with oxygen ​ It will relight ○​ Testing for hydrogen molecules ​ Relies on the fact that hydrogen burns to give water ​ Light wooden splint ​ Place lit end under test tube filled with hydrogen and air ​ Upside down, 45º ​ Pop is heard ​ Hydrogen + Oxygen → Water (H + O = H2O) ○​ Testing for ammonia ​ Relies on the fact that it’s the only alkaline common gas ​ Use most litmus or indicator paper ​ Moist as ammonia is very soluble and we want it to dissolve in the moisture and react with the acid-base indicator saturated into the paper ​ Pour ammonia solution into a boiling tube ​ Heat it gently in hot water bath ​ Use red litmus paper and put it into the boiling tube ​ Turns blue ​ Turns blue because it is alkaline (Red + Alkaline = Blue) ○​ Testing for water ​ Two ways ​ Anhydrous cobalt chloride ​ Anhydrous copper sulfate ​ Anhydrous cobalt chloride: ​ Put water onto the cobalt chloride paper ​ Paper turns pinkish-white ​ Anhydrous copper sulfate: ​ Put copper sulfate into test tube ​ Add water ​ Copper sulfate should turn blue ○​ Testing for chlorine ​ Chlorine is a very powerful oxidising agent ​ Reacts with many coloured compounds and bleaches them  ​ Chlorine gas is produced by reacting hydrochloric acid and manganese dioxide, creating manganese dichloride, chlorine gas, and water ​ Put blue litmus paper on tile ​ Add one drop of chlorine water ​ Blue litmus paper turns red ​ Creates white spot that expands over time because chlorine is bleaching it ○​ Testing for iodine ​ Put 1-2 drops of iodine solution in a tile ​ Put 1-2 drops of starch solution ​ Creates a blue-black complex ​ Atoms, Moles, and Molecules – I can describe each word and expand on their concepts. ○​ Atom ​ Smallest, electrically neutral, particle of an element that can take part in a chemical change ○​ Molecule ​ Smallest, electrically neutral, particle of an element or compound that can exist on its own ○​ Ion ​ An atom, or group of atoms, which carries an electric charge ○​ PLEASE UNDERSTAND: ​ A single atom, O, cannot exist on its own ​ A single atom can exist when combined with something else, but then it is part of a molecule ​ An oxygen molecule has two oxygen atoms, O2 ​ A few elements exist as single atoms ​ An atom, therefore, is the same as a molecule ​ Ex. Helium ○​ Relative atomic mass, Ar ​ The weighted average of the masses of an element’s isotopes in comparison to the mass of carbon-12 ​ No units ○​ Relative molecular mass, Mr ​ Adding together the relative atomic masses of the atoms in the chemical formulae ​ Ex. H2O ​ H: 1 ​ O: 16 ​ Mr = (1x2) + 16 ​ Mr = 18  ○​ Relative formula mass ​ Simplest ratio of the atoms in the compound ​ Usually refers to ionic substances ○​ Mole ​ Mass of an atom is very small ​ Not used in calculations ​ Convert the relative mass into a unit quantity called a mole ​ Each mole is 6.02 × 10^23 ​ Avogadros number ​ Number of atoms in 12g of Carbon-12 ○​ Molar masses ​ Finding the molar mass of oxygen ​ Molecule contains 2 atoms of oxygen each of mass 16 ​ 2 x 16 ​​ = 32g mol^-1​ ​ ^-1 = per atom ​ Total mass ​ = 32g mol^-1 ​ Finding the molar mass of nitrogen ​ 2 x 14​ ​ = 28g mol^-1 ​ Finding the molar mass of sulphuric acid, H2SO4 ​ 2 atoms of hydrogen each of mass 1​ = 2 x 1 = 2g mol^-1 ​ 1 atom of sulfur of mass 32​ ​ = 1 x 32= 32g mol^-1 ​ 4 atoms of oxygen of mass 16​​ = 4 x 16= 64g mol^-1 ​ Total mass ​ ​ ​ ​ = 98g mol^-1 ​ Finding the molar mass of hydrogen bromide ​ 1 + 80 = 81 mol^-1 ​ Finding the mass of hydrogen bromide ​ 81 ÷ 6.02 × 10^23 = 1.35 × 10^-22 ​ Rates of Reaction – I can describe the rate of reaction and factors that have an effect on it. ○​ Three factors are almost always instinctively thought of when speeding up a reaction ​ Temperature ​ Heating something up ​ Concentration ​ Increase the concentration of at least one reactant ​ Surface area ​ Crush solid lumps into a powder ○​ Industrial chemists are very interested in how fast reactions go ​ If a chemical reaction is of benefit, the faster we can get it to go the better ○​ Following a reaction ​ In a chemical reaction, reactants are converted into products  ​ In order to follow a reaction, observe changes that take place ​ Either due to a reactant being used up or due to a product being formed ​ Examples: ​ Formation or dissolving of a precipitate ​ Formation or dissolving of a coloured substance ​ Formation of a gas ​ When comparing the rates of a particular reaction under different conditions ​ Take the time required for a fixed amount of reaction to occur ​ Examples: ​ The time taken for a clear solution to form a precipitate of a definite turbidity (cloudiness) ​ The time taken for a colourless solution to produce a colour of a particular intensity ​ The time taken for a given volume of gas to be produced ○​ Collision theory ​ We need to understand this principle in order to look at how different factors affect the rate of reaction ​ In any liquid or gas sample, particles are in rapid random motion ​ Results in collisions between particles ​ For a reaction to occur: ​ Particles that can react collide with each other ​ They must collide with sufficient energy to break bonds that need to be broken ​ In short: ​ In order for a reaction to occur, there must be a collision between reactant particles and must have sufficient energy and the correct orientation ○​ Surface area calculations ​ Diagram of a 3x3x3 cube ​ 3 x 3 x 6 = 54 cm2 ​ Same volume but in 1x1x1 cubes ​ 27 x 6 = 162 cm2 ○​ Following the progress of a reaction by volume of gas  ​ Can the volume of gas produced in a chemical reaction be used to follow the process of a reaction? ​ Calcium carbonate + Hydrochloric acid → Calcium chloride + Carbon dioxide + Water ​ CaCO3 + HCl → CaCl2 + CO2 + H2O ​ Method: ​ Put 20 cm3 of hydrochloric acid in a side arm tube ​ Weigh 4.0g od small marble chips ​ Add marble chips to acid, replace bung, and start stopwatch ​ Record volume of carbon dioxide produced at the end of each 5 second period ​ Continue until time limit is reached ​ Observable change: ​ The formation of has and how much gas is produced by a given time ​ Diagram: ​ Graph rises at a steady rate and plateaus towards the end of the reaction ​ The volume of gas produced over time is rapid in the beginning and eases off at the end and plateaus, and the reaction is over when the curve flattens ○​ Effect of surface area on reaction rate ​ What is the effect of surface area on the reaction time while following the progress of a reaction by mass loss? ​ Calcium carbonate + Hydrochloric acid → Calcium chloride + Carbon dioxide + Water ​ CaCO3 + HCl → CaCl2 + CO2 + H2O ​ Method: ​ Put 70cm3 of hydrochloric acid ​ Add 30cm3 of water ​ Transfer solution into flask ​ Place flask on scale ​ Take five antacid tablets and break each in quarters ​ Place the tablets in a container and put it on the scale ​ Note total mass  ​ Add the tablet pieces to the acid and start the stopwatch simultaneously ​ Record mass in the results table and mass lost as CO2 at the start and at the end of each 30-second period ​ Continue until 4 minutes ​ Repeat with five whole tablets ​ The greater the surface are the faster the reaction ○​ Effect of concentration on reaction rate ​ What is the effect of concentration on reaction rate? ​ Magnesium + Hydrochloric acid → Magnesium chloride + hydrogen ​ Mg + HCl → MgCl2 + H ​ Observable change: ​ How long it takes for the magnesium to dissolve ​ Method: ​ Sand the 6cm strip of magnesium till shiny ​ Put 50cm3 of acid into a conical flask ​ Add 1cm of the magnesium strip in the acid and start the stopwatch ​ Swirl the flask occasionally to speed up the reaction ​ Once dissolved, note down the time and repeat with other acid concentrations ​ Asymptote graph is reached, curve never touches either axis ​ Collision theory, things need time to move so time cannot be zero ​ The higher concentration of acid the faster the reaction ○​ Effect of temperature on reaction time ​ How does temperature affect the reaction rate? ​ Method: ​ Fill beaker with chilled water to the 150cm3 graduation ​ Use thermometer to measure temp of water and record it ​ Drop an Alka-Seltzer (or vitamin C tablet) into the beaker and start stopwatch ​ Stop when tablet has completely dissolved and record time in seconds ​ Repeat with other water temperatures ​ What happened to the tablets? ​ They would dissolve in the water and fizz ​ Why is it a chemical change? ​ There is fizzing which means carbon dioxide is produced ​ In which beaker was the reaction the slowest and fastest? ​ The coldest and hottest respectively  ​ The hotter the temperature, the quicker the reaction rate ○​ Effect of catalysts on reaction rate ​ Rate of reaction can be increased by adding a catalyst ​ Catalyst: A substance that increases the rate of a chemical reaction, but is not used up ​ Reduces the amount of activation energy required ​ Balance Chemical Equations – I can balance chemical equations. ○​ Four main rules ​ Check that all the formulae in the equation are correct ​ Deal with one element at a time ​ Balancing is adding big numbers, not small ​ Check each element again and go back to rule 3 if needed ○​ Example 𝐶4𝐻8 + 𝑂2 → 𝐶𝑂2 + 𝐻2𝑂 ○​ Unbalanced! ​ Four carbon atoms on the left, only one on the right. ​ Add a four in front of the C. on the right ​ ​ 𝐶4𝐻8 + 𝑂2 → 4𝐶𝑂2 + 𝐻2𝑂 ○​ Unbalanced! ​ Eight hydrogen atoms on the left, only two on the right. ​ Add a four in front of the H on the right. 𝐶4𝐻8 + 𝑂2 → 4𝐶𝑂2 + 4𝐻2𝑂 ○​ Unbalanced! ​ There are two oxygen atoms on the left, but because four are in front of 4CO2, the formula is 4 × C + 4 × O2, which is eight oxygen atoms. The same applies to 4H2O, which has 12 oxygen atoms. ​ Add a six in front of the O on the left. ​ ​ 𝐶4𝐻8 + 6𝑂2 → 4𝐶𝑂2 + 4𝐻2𝑂 ○​ Done! ○​ Example 𝐶𝑢 + 𝑂2 → 𝐶𝑢𝑂 ○​ Unbalanced! ​ Two oxygen on the left, only one on the right. ​ Add 2 in front of CuO. ​ ​ 𝐶𝑢 + 𝑂2 → 2𝐶𝑢𝑂 ○​ Unbalanced! ​ One copper on the left, two on the right ​ Add 2 in front of Cu 2𝐶𝑢 + 𝑂2 → 2𝐶𝑢𝑂  ○​ Done! **Please do not only study from this study guide. Experiments and diagrams are not in detail.**