Y9 Yearly All Subject Notes PDF
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These are some notes on electrochemistry for year 9 students. The notes look like general notes rather than a past paper. No exam board or date was visible.
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Chemistry C4 Electrochemistry 4.1 Electrolysis C (4.1.1) Electrolysis:Decomposition of an ionic compound,when molten or in aqueous solution, by the passage of an electric current - Possible in liquid metals and graphite due to free electrons that can move around imple el...
Chemistry C4 Electrochemistry 4.1 Electrolysis C (4.1.1) Electrolysis:Decomposition of an ionic compound,when molten or in aqueous solution, by the passage of an electric current - Possible in liquid metals and graphite due to free electrons that can move around imple electrolytic cells S (4.1.2) Parts: - Electrolyte: Molten or aqueous substance undergoing electrolysis - Direct current: Supplied by battery or power source - Electrolytic cell: Apparatus used for electrolysis that converts electrical energy to chemical energy - Electrodes: Points where electric current enters or leaves a battery/electrolytic cell (graphite often chosen due to unreactive nature) - Anode: Pos electrode - Cathode: Neg electrode How it works: 1. Electrons flow from neg to pos terminal of battery 2. Ions move to carry current in electrolyte 3. Pos ions (cations) move to neg cathode, neg ions (anions) move to pos anode Comparing metallic and electrolytic conductivity ( 4.1.4) Transfer of Charge Charge is transferred in a number of different ways to allow current to flow in complete circuit 1. Movement of electrons in external circuit - In wires outside liquid, charge transferred by electron movement away from neg battery terminal towards pos 2. Loss or gain of electrons at electrodes - Cathode: Electrons more from electrode to cation, forming uncharged species - Anode: Electrons move from anion to electrode, forming uncharged species 3. Movement of ions in electrolyte - In electrolyte charge is transferred by ions, not electrons - Pos ions move towards cathode (likes attract) - Neg ions move towards anode (likes attract) ( 4.1.3) Electrolysis Examples - Determining Products Molten Lead (II) Bromide 1. Derive formula of electrolyte - PbBr2 2. Derive chemical equation for gaseous product - Br2 3. Write half equations for products at cathode and anode - Pb2+ + 2e- → Pb (l) - 2Br- - 2e-→ Br2 4. Write balanced equations with states - Pb2++ 2Br-→ Pb (l) + Br2 (g) Dilute Sulfuric Acid - Few drops of sulfuric acid to water allows electrolysis to occur - Water is poor conductor of electricity - Limited ions - Requires Hofmann Voltameter: Keeps gases produced from water separate - Hydrogen produced at cathode moves into tube above cathode; oxygen produced at anode moves into tube above anode in ratio 2:1 - Ratio of hydrogen to oxygen in a single water molecule - Ions present in solution: H+, OH-, SO42- - At each electrode, only 1 ion can be discharged - OH- and SO42 - both move to cathode by only hydroxideis discharged due to relative ion stability - 2H2O (l) → 2H2 (g) + O2 (g) Aqueous sodium chloride - 4 different ions: Na+, Cl-, OH-, H+ - ydrogen gas produced at cathode, chlorine gas produced at anode H - NOTE: Products of molten sodium chloride different to aqueous sodium chloride solution Molten ionic compounds - Molten salts: Heat needed to ensure substance can conduct electricity - (4.1.6) General product rules - Product at cathode: metal solid/hydrogen (first substance listed in chemical formula) - Product at anode: non-metal gas (second substance listed in chemical formula) - Movement of ions to different electrodes results in breakdown of ionic compound Aqueous solutions (incl. acids) - Products different to molten substance electrolysis as water also breaks into ions H2 O → H+ + OH- - Hydrogen and hydroxide ions compete with ions from acid or salt to be discharged at electrodes - Example: Concentrated sodium chloride solution produces hydrogen gas and chlorine gas (4.1.5) Aqueous copper (II) sulfate - Use of inert/unreactive carbon/graphite electrodes produces deposit of copper metal on cathode - Copper is less reactive than hydrogen - therefore discharged at cathode - At cathode: Cu2+ (aq) + 2e- → Cu (s) - Hydroxide ions are discharged, not sulfate ions - 4OH- → 2H20 + O2 + 4e- - Observations: Blue solution colour will fade as copper ions causing colour are discharged. Electrolyte solution will become more acidic as hydroxide ions are discharged - Use of copper electrodes (not inert): - Cathode gains mass as copper is deposited on electrode - Cathode: Cu2+ (aq) + 2e- → Cu (s) - Anode loses mass as copper dissolves from electrode: - Anode: Cu (s) → Cu2+ (aq) + 2e- - Reasoning: Electrons are being taken away from electrode, therefore, electrons from uncharged copper atoms are taken away to form pos charged copper ions - Blue solution colour does not change because concentration of copper ions stays constant in solution ( 4.1.8) Ionic Half-equations Anode: Anion gives up electrons to become neutral - Non-metal ions - Example: Cl- gives up 1 electron to become Cl - OXIDATION Cathode: Cation accepts electrons to become neutral atom - Metal ions - Example: Mg2+ accepts 2 electrons to become Mg - REDUCTION 4.2 Hydrogen-Oxygen Fuel Cells C What is a fuel cell? uel cell: Device that continuously converts chemical energy into electrical energy using a F chemical reaction (4.2.1) Hydrogen-Oxygen fuel cell: Uses combustion reaction between hydrogen and oxygen gas to create energy for electricity, with water as the only product - 2H2 (g) + O2 (g) → 2H2O (l) (4.2.2) Advantages and disadvantages of the hydrogen-oxygen fuel cell: - Advantages: - Clean fuel - only waste product is water - Non-toxic - Lower flammability than petrol - Uses more efficient technology - Convenient for heavy transport and trains - Produces more energy per gram than any other fuel - Disadvantages - Difficulty in managing safe storage and transportation of hydrogen gas - Need for greater distribution of hydrogen filling stations - Difficulty in production of fuel cells - Large fuel-tank required C5 Chemical Energetics 5.1 Exothermic and Endothermic reactions C Introduction Energy may be transferred during chemical reaction due to change in chemical bonds (5.1.1)Exothermic reaction: Chemical reaction inwhich thermal energy is released into surroundings → leads to temp increase of surroundings - Makes it feel hot - EXothermic means energy EXits reactions (5.1.2)Endothermic reaction: Chemical reaction thatabsorbs thermal energy from surroundings → leads to temp decrease of surroundings - Makes it feel cold - ENdothermic means energy ENters reaction (5.1.3) Reaction Pathways Diagrams/Energy Level Diagrams Exothermic reaction: - Energy of reactants is higher than energy of products - Black arrow points down - Shows energy release Endothermic reaction: - Energy of reactants lower than energy of products - Black arrow points upwards to show that energy is absorbed ( 5.1.4) Enthalpy Change Enthalpy: Thermal energy content of system Enthalpy change: Transfer of energy during a reaction (∆H) - Exothermic: Enthalpy change is neg - Endothermic: Enthalpy change is pos ( 5.1.5) Activation energy Activation energy: Minimum energy required for the colliding particle to react(cause a chemical reaction to occur) - Varies for diff chemical reactions - Seen on energy level diagrams - Important, as some bonds must be broken before new bonds can be formed Most reactions are exothermic, though some are totally spontaneous - Often, additional energy required to start reaction (activation energy) - Example: Burning wood requires lit match or spark to begin reaction (5.1.6) How to draw reaction pathway diagrams 1. Label axes - X-axis: Reaction coordinate - Y-axis: Energy 2. Draw reactant and product lines 3. Add hump 4. Label activation energy and enthalpy change ( 5.1.7) Bond breaking and making Apart from noble gases, most substances involved in chemical bonding - During chemical reaction, intramolecular bonds in reactant molecules need to be break and reform - Requires energy (absorbed from surroundings) - Therefore bond breaking is endothermic - New bonds formed to make products (releases energy) - Therefore bond making is exothermic tronger bonds require more energy to break, and release more energy when new bonds S are formed (higher bond energy) - In exothermic reactions, bonds in products are stronger than reactants - Energy absorbed to break reactant bonds < energy released to make product bonds ond breaking: Requires absorption of energy - endothermic B Bond making: Releases energy - exothermic C6 Chemical Reactions 6.1 Physical and chemical changes C (6.1.1) Intro Physical change: - No new substance formed - Substances present remain chemically unchanged - Often easy to reverse - Often easy to separate - Can involve heat being taken in or given out Chemical change: - Result of chemical reaction where new substance is formed - Often difficult to reverse - Energy can be given out or taken in e.g. light; heat .2 Rate of Reaction 6 (6.2.1) Rate of reaction Reaction rate: Measure of how fast a reaction takes place (how fast reactants become products) Factors affecting reaction rate: - Concentration of reactant solutions - More particles per volume means faster reaction rate - Pressures of gaseous reactions - Increasing pressure = less space between particles = increased frequency of collisions = increased chance of successful collisions - Surface area of any solid reactants - Increasing amount of area = more exposure of reactant particles to each other = more opportunities for successful collisions - Temperature - Increasing temp = increased KE of particles = faster particle movement = more frequent collisions - Increased KE of particles = more collisions overcoming activation energy barrier - (6.2.2) Catalyst - Alternative reaction pathway with lower activation energy = greater proportion of collisions are successful - (6.2.6) Lowers energy barrier for successful collisions - Remains unchanged at end of reaction - Is not another ‘reactant’ - Does not get used up - Can be reused ( 6.2.7) Collision Theory Collision Theory: explains how chemical reactions occur based on collisions between reacting particles Must fulfil 2 criteria for reaction to occur: - Correct orientation of reactant particles - Must have enough energy to break chemical bonds of reactants (minimum energy requirement called activation energy) ate of reaction depends on success rate of reactant particle collisions R Factors affecting rate: - Number of particles per volume (concentration) - More particles = higher chance of collisions = higher chance of successful collisions - Frequency of collisions - KE of particles - Activation energy (6.2.3) Practical methods of investigating rate of reaction 1. How quickly reactants are used up 2. How quickly products are formed Properties that change during reaction: - Gas production (measure volume of produced gas) OTE: Use different size pieces of magnesium ribbon with same total mass N and measure volume of gas produced in fixed time - olour or turbidity change C - Mass change (6.2.4) Interpreting rate of reaction graphs: 6.3 Redox C Intro (6.3.1) Redox reactions: Involves simultaneous oxidation and reduction - (6.3.3) Redox reactions involve gain and loss of oxygen - (6.3.2) Oxidation = gain of oxygen; Reduction = loss of oxygen - Reactant that gains oxygen in product is oxidised; reactant that loses oxygen in product is reduced ( 6.3.5) (6.3.6) Oxidation and Reduction with electrons Oxidation number: Roman numerals next to chemical name - Same as pos charge on metal ion Oxidation: Loss of electrons/Increase in oxidation number Reduction: Gain of electrons/Decrease in oxidation number Oxidising agent: Oxidises another substance (becomes reduced itself) - Non-metal Reducing agent: Reduces another substance (becomes oxidised itself) - Metal (6.3.4) Identifying oxidation and reduction in redox reactions: - Oxidation: Charge increases/Oxidation number increases - Reduction: Charge decreases/Oxidation number decreases Biology B6 Plant Nutrition 6.1 Photosynthesis B Intro (6.1.1) Photosynthesis: Process by which plants synthesis carbohydrates from raw materials using energy from light - Plants make carbohydrate glucose (stored as insoluble starch) in chloroplasts (found in leaves) ( 6.1.2) Equations: Carbon dioxide + water → oxygen + glucose in presence of light and chlorophyll (6.1.5) 6CO2 + 6H2O → C6H 12O6 + 6O2 in presence of light and chlorophyll (6.1.3) Chlorophyll: Green pigment found in chloroplasts - (6.1.6) Transfers energy from light into energy in chemicals for carb synthesis ( 6.1.7) Uses of glucose Sucrose: For transport in the phloem Nectar: To attract insects for pollination Starch: Energy storage Cellulose: Building cell walls Glucose: Respiration - to release energy in cells (found in potatoes & leaves) Proteins: Growth ( 6.1.8) Ions Glucose combines with soil minerals to make compounds - Nitrates make amino acids for proteins - Magnesium ions make chlorophyll for photosynthesis ( 6.1.4) (6.1.9) Rate of Photosynthesis Light as limiting factor: 1. As light increases, photosynthesis rate increases 2. Increasing amount of light has no effect on photosynthesis rate 1. As temp increases, photosynthesis rate increases (photosynthetic enzymes work best in warmth) 2. Plant enzymes denature at approx 45 degrees Celsius (photosynthesis stops and rate falls to 0) . As amount of carbon dioxide increases, 1 photosynthesis rate increases 2. Increasing the amount of carbon dioxide has no effect on rate of photosynthesis ( 6.1.10) Hydrogencarbonate indicator solution & gas exchange Hydrogencarbonate indicator: Detects increases and decreases in carbon dioxide concentration - RED: Normal - YELLOW: Increase - PURPLE: Decrease In bright light: Rate of photosynthesis exceeds rate of respiration - Net gas exchange: carbon dioxide into leaf; oxygen out of leaf - Carbon dioxide levels drop, turning indicator purple In low light: Rate of photosynthesis and rate of respiration equal (compensation point) - No net gas exchange - No change in carbon dioxide level → indicator remains red In darkness: Only respiration occurs, as there is no light for photosynthesis - Gas exchange: Oxygen into leaf; carbon dioxide out - Increase in carbon dioxide levels, turning indicator yellow 6.2 Leaf structure B (6.2.2) (6.2.1) (6.2.3) Leaf adaptations for photosynthesis B8 Transport in Plants 8.1 Xylem and Phloem B (8.1.1) Intro Xylem Phloem What do they transport? Water + minerals Sugars Which direction? Up Up + Down Alive or dead? Dead Alive Waterproof? Yes No (8.1.2) Identifying in diagrams: B8.2 Water uptake oot hair cells R Appearance: Tiny hairs covering ends of smallest roots (8.2.2) (8.2.1) Function: Provide large surface area for absorption of water and mineral ions by process of osmosis (8.2.3) Pathway: 1. Root hair cell - Water moves cell-cell to root cortex 2. Root cortex - Moves cell-cell by osmosis down concentration gradient - Each cell has lower water potential than the one before it - In root centre water enters xylem vessels 3. Xylem - Water moves up xylem to leaves 4. Leaves - Water moves cell-cell into mesophyll cells to be used for photosynthesis 5. Air - Exits leaf via due to photosynthesis - May evaporate and diffuse through air spaces in mesophyll cells and out through stomata 8.3 Transpiration B Intro (8.3.1) (8.3.2) Transpiration: Loss of water vapour from plant leaves by evaporation of water at surfaces of mesophyll cells followed by diffusion of water vapour through stomata (8.3.3) (8.3.4) Transpiration rate factors: - Temperature - Warmer = faster transpiration - More KE of particles to evaporate and diffuse out of stomata - Humidity - More humidity = slower transpiration - Moisture in air causes minimal concentration gradient between inside and outside of leaf - Diffusion works best when there is a big difference in concentration between 2 places - Wind speed - More wind = faster transpiration - Wind sweeps away water vapour - Wind maintains low concentration of water in outside air - Improves diffusion speed ilting W If transpiration occurs quickly, plant may lose water faster than it can take in at roots - Cells lose water (become flaccid; lose turgidity), becoming soft and floppy otometer P Measures uptake of water by plant - Records distance an air bubble moves in a closed straw of water and a plant 8.4 Translocation B Translocation Translocation: Movement of sucrose and other substances like amino acids around a plant - Glucose produced in leaves is converted into sucrose - Transported around plant in phloem - Must be able to reach all cells so sucrose can be converted back into glucose for respiration Sources: Parts of plants that release/make sucrose or amino acids Sinks: Parts of plants that use or store sucrose or amino acids B9 Transport in animals 9.1 Circulatory systems B Circulatory systems Circulatory systems: System of blood vessels with pump and valves to ensure one-way flow of blood Fish - single circulation: - 2 chambered heart which pumps blood → gills → body → back to heart Mammal - double circulation: - 4 chambered heart - Blood pumped to lungs to pick up oxygen before returning to heart - Oxygenated blood pumped to all body cells Advantages of double circulation: - Single-circulation system causes loss of blood pressure - Oxygen delivered more efficiently as higher pressure makes blood movement faster 9.2 Heart B Effect of exercise on body (9.2.4) Response to exercise (description) - Heart - Heart rate increases - Arteries dilate - Increased blood flow to muscles - Increased supply of oxygen and glucose to muscles - Increased removal of carbon dioxide from muscles - Lungs - Breathing rate increases - Breathe more deeply - More oxygen picked up by red blood cells - More oxygen taken to muscles - More carbon dioxide removed and breathed out ( 9.2.5) Response to exercise (explanation) Heart - Physical response due to need for more oxygen and glucose to be delivered to cells - Respiration to produce additional energy Lungs - Physical response due to need for more oxygen to be taken into lungs - Moves into blood for respiration for additional energy (9.2.1) Parts NOTE: Observe oxygenated and deoxygenated - Right ventricle and atrium is deoxygenated, left atrium and ventricle is oxygenated athway of blood P Left atrium → left ventricle → aorta →vena cava → right atrium → right ventricle → pulmonary artery→ lungs → pulmonary vein (9.2.3) Monitoring heart activity - Pulse rate - Sound of valves closing (lub dub) - ECG (electrocardiogram) oronary heart disease C (9.2.5) CHD: Blockage of coronary arteries - Supply heart with glucose and oxygen for respiration - Atheroma: Fatty deposit that forms in artery walls - Cholesterol deposits build up → Causes stiffening of artery walls; lumen narrowing → restricts flow of blood → cause blockage → blood pressure increases → damage to artery lining → blood clot: collection of platelets Risk factors: - Smoking - (9.2.6) Diet - Replace animal fats with plant oils - Lack of exercise - Exercising improves fitness, prevents weight gain and decreases blood pressure - Age - Males - Stress - Genetic predisposition Myocardial infarction/heart attack: Reduced supply of oxygen to heart muscle - ymptom of CHD S - Result of coronary artery blockage - May cause heart to stop beating if blockage is close to junction of coronary artery and aorta 9.3 Blood vessels B Summary Arteries Veins Capillaries Diagram Blood direction Away from heart Towards heart Towards heart Blood pressure igh (due to push H Low - from ventricles) Wall structure uscular thick wall M Flexible - (3 layers) Wall thickness Thick Thin One cell thick Internal diameter Small Large Very narrow (lumen) compared to other blood vessels Valves present? No es (low blood Y - pressure needs valves to prevent backflow) lood oxygenated or Oxygenated B eoxygenated D llows transport of A deoxygenated? (apart from oxygen pulmonary vein) 9.4 Blood B (9.4.1) (9.4.3) Components of blood (Most common type) Red blood cells: Transport oxygen; haemoglobin - Haemoglobin: Large protein molecule folded around 4 iron atoms - In high oxygen concentrations, forms oxyhaemoglobin - In low oxygen concentrations, reverses to become haemoglobin and oxygen Plasma: Transports all types of blood cells; carbon dioxide; urea; nutrients; ions; hormones (9.4.5) White blood cells: Defence against disease; clears up dead body cells - Phagocytosis: Destroying pathogens by engulfing and digesting them - Lobed nucleus - Lymphocytes: Produce antibodies which attach to and destroy pathogens - Large round nucleus Platelets: Blood clotting - (9.4.6) Blood clotting: Fragments of cells with no nucleus - Stops pathogens entering body through breaks in skin - Prevents blood loss
