F.2 Integrated Science 1st exam Notes 2007.doc

F.2 Integrated Science 1st Examination Notes 2007-2008By Suki Wong 2B (35)Ch.5 Matter as Particles-Part IISection C.2: Elements and Compound, Atoms and Molecules1. Elements: a) Fundamental substances which cannot be broken down into anything simpler by what chemical means.b) Made of only 1 kind of atomsc) No. of elements-occur naturally: 92 -made by scientist: 25 -Total: 117 2. Atom: The smallest particle of an element that has the properties of that element3. Compound:a) A new product formed when 2 or more elements are chemically joinede. g. water (H2O), carbon dioxide (CO2), table salt (NaCl)b) Lose their individual propertiesc) Have different properties from the elements it is composed of4. Molecule: a) The small particle of a substance that exists independently in normal condition.Molecule made up of-only 1 atom of that element: noble gases) -2 atoms of that element: oxygen (O2), nitrogen (N2), hydrogen (H2)5. Mixtures:a) 2 or more substances that are mixed together physically but not chemically joined.e.g. salt solutionb) Still keep the characteristics of that element.Section C.3: Atomic Structure:Atom consists of smaller sub-atomic particles:Protons, Neutrons and ElectronsTable 1 Sub-atomic particlesName of particleSymbolPosition in atomCharge(relative to that on a proton)Relative MassProtonpInside the nucleusPositively charged (+ve)1NeutronnInside the nucleusneutral1Electrone-Moving around the nucleus in high speedNegatively charged (-ve)1/1840When atoms join together to form molecules, the number and arrangement of electrons may change, but the nucleus will not changeAtomic Number: a) Atomic Number= Number of protons= Number of electronsb) Mass number= Number of Protons+ Number of Neutronsc) An atom is neutral by itself.d) A change in an atomic number results in a different elemente.g. carbon (atomic no.: 6) is a black solid while nitrogen (atomic no.: 7) is a colourless gas20 simplest elements (must revised)Table 2 Number of sub-atomic particles in the 20 simplest elementsAtomSymbolNumber of protons(atomic number)GroupNumber Numberof neutrons Number of electronsMass Number(no. of protons+ neutrons)HydrogenH1/011HeliumHe2/224LithiumLi31437BerylliumBe42549BoronB536511CarbonC646612NitrogenN757714OxygenO868816FluorineF9710919NeonNe108101020SodiumNa111121123MagnesiumMg122121224AluminiumAl133141327SiliconSi144141428PhosphorusP155161531SulphurS166161632ChlorineCl177181735ArgonAr188221840PotassiumK191201939CalciumCa202202040Section D: Gas Pressure1. Gas Pressure: a) Set up by Millions of air particles move rapidly and constantly hit the wall of the syringeb) Can be measured by: Bourdon gaugec) Unit: pascal (Pa)d) Keep things like tyres, balloons and basketball inflated.2. Factors affecting gas pressure:a) Volumeb) No. of gas particles c) TemperatureWhen volume decreases/no. of gas particles increases/temperature increases while other factors remain unchanged, gas pressure increases.When volume increases/no. of gas particles decreases/temperature decreases while other factors remain unchanged, gas pressure decreases.3. Air Pressure: The exertion of pressure when an object is hit by air particlesSection E: Density1. Mass: a) A measure of how much matter there is in an object or substanceb) All substances have massc) Measured in kilogram, kg or gram, g.2. Density: a) Density of a substance=mass per unit volumeSo Density (d) = Mass (m)/Volume (v)b) unit: gram per cm3g/cm3If volume remains unchanged and the mass increases, the density increases.If mass remains unchanged and the volume increases, the density decreasesLess dense substances float on denser ones.Section F: Thermal Expansion and Contraction1. Expansion: When substances are heatedthe particles move vigorously space further apartsolid, liquid, gas expand on heating2. Contraction: When substances are cooledthe particles gather close togetherthe substances contract on cooling.(Expand the least) solidsliquidsgases (Expand the most)Applications of thermal expansion and contraction in daily life1. Railway lines: There are gaps left between the lengths of rail. This allows the rail to expand in the summer. Otherwise the rails may bend, causing accidents.2. Flyovers: Flyovers are made of strong concrete sections. Gaps are left between sections to allow expansion in summer.3. Overhead wires: When an electric company installs overhead wires in the summer, they should be slack enough because they will contract in winter.4. Bridge rollers: One end of a bridge is fixed and the other and rests on rollers and there is also a gap. These allow a bridge to move during expansion.5. Thermometers: The most common thermometers are liquid-in-glass thermometers. The temperature is indicated by the expansion and contraction of the liquid inside the thermometer. Usually, the liquid inside the glass is mercury but alcohol is also used. Ch.6 Water the solventSection A: Heavy demand for clean water supplySection A1: importance of water1. Water: a) Most common liquid on the Earthb) formula: H2Oc) 3/4 of our planet is covered with waterd) All plants and animals cannot survive without water because cells are made up largely of watere) Makes up 60-70% of our body weightf) 90% of our blood is made up of waterg) Contents in different living things varyh) Necessary for keeping the living cells in proper functions.Section B: Water Purification1. most of the water reserve on Earth is not suitable for drinking2. fresh water that is suitable for drinking: less than 1/2003. most of the fresh water is stored deep underground4. untreated water(raw water) contains many kinds of impuritieseven the water is extractedstill unsafe for us to drink directlySection B.1: Impurities found in raw water1. Insoluble impurities: cannot dissolve in water, e.g. sand, mud and oil.2. Soluble impurities: can dissolve well in water, e.g. salts and dyes.3. Micro-organism: living organism which are too small to be seen with naked eyes but can be observed under the microscope, e.g. Amoeba and E. coli (can cause intestinal disease in humans)How to make water safe to drink?We need to remove the above impurities by water purification.1. Water purification: removing impurities in order to make it becomes pure. Impurities in different kinds of water:Possible ImpuritiesDistilled WaterMuddy pond waterSea waterTap waterInsolubleNoYesYesNoSolubleNoYesYesYesMicro-OrganismsNoYesYesYesSection B.2 Water purification in Hong KongHong Kongs water supply: 20% from rainwater and 80% from Dongjiang water (river).Possible impurities in the water: 1.Mud( insoluble)2.Sands (insoluble)3.Minerals (soluble)4.Bacteria( micro-organisms)Section B.3: Water purification methodsNature of the impurities to be removedName of the methodLargeFineInsolubleSoluble=)=)Sedimentation=)=)Filtration=)=)=)=)DistillationAlum: a kind of crystal which can stick the insoluble impurities like a piece of magnet. As the mass increases while sticking insoluble impurities, the volume remains unchanged and the density increases, finally it sinks to the bottom of the container and becomes sediment.1. Sedimentation:a) Process: add alumstir wellinsoluble impurities sinkform a layer of sedimentthe upper portion becomes clearerb) the deposition by settling of a suspended materialc) simplest method for purifying water with insoluble impuritiesd) first step of water purification2. Filtration: a) Process: mixturefilter paper(folded)filter funnelfiltrateb) the method of purifying water by passing water through a filter to remove large or suspended particles.c) The filtered water is still not suitable for drinking as it still contains soluble impurities and some harmful micro-organismsd) We usually use filter paper and filter funnel for filtration in the laboratory.e) the liquid which goes through the filter: filtratef) the solid substance remaining on the filter: residue Method of examining whether the filtered water is pure:Process: filtered water(on the watch glass)boilingevaporatesResult i) White solid impurities are left on the watch glassthe water contains soluble impurities and micro-organisms=(Result ii) Nothing is left pure watersafe to drink=)3. Distillation:Anti-bumping granules: prevent the boiling tube from cracking and thus smoothen the process.a) Process: Bunsen burnerheat up the coloured waterevaporatessteamdelivery tubecondensesdistillate(pure water)b) Use of distillation: to isolate the solvent (water) from the solution(coloured water) which contains soluble solutes.4. Fractional distillation:a) Process: Mixture (water-ethanol mixture)fractionating column(a boiling tube contains a lot of glass beads)evaporation and condensation i) liquid with lower b. p. steaminner layer of the condenser(outer layer: tap water)condenseswater dropsfilter funneldistillate(pure water)ii) liquid with higher b. p. stays in the fractionating columnb) Condenser: Function: to make sure all the steam condensate & become water before it go through the filter funnel & wont have any chance to escape while also to speed up the process of condensationWater went in from the bottom of the condenser and came out from the top of it to make sure that the tap water can flow all over the condenser. If the water went in from the top & went out from the bottom, it will go out from the bottom.c) Function of glass beads in the fractionating column:i) provide a larger surface area for repeated condensation & evaporationii) ensure only steam of 1 substance can pass through the fractionating columniii) ensure the temperature measured is fixed out sharphelp us to check the boiling point of the distillate more accurately d) Why was the thermometer bulb place in the fractionating column?It is placed at that position so as to record the temperature of the steam that actually distilled over and collected. This temperature is the boiling point of the distillate.General process of Distillation:Boiling CondensationImpure water-steam-distillate(purified water) (heating) (cooling)Distilled water: purified water through the process of DistillationComparing Fractional distillation and DistillationNameFunctionProcessFractional distillationSeparate a mixture of 2 kinds of liquid(2 different boiling point)For example the b.p. of liquid A is 100c while liquid B is 200c. When the temperature reaches 100c. Liquid A evaporates so the 2 liquids can be separated.DistillationPurifying liquidAs the b.p. of water is 100c. If the temperature reaches 100c. The water evaporates and turns into steam. By collecting the steam and condenses it, we can get distilled water.4.Boilinga) simplest method of water purificationb) can kill most of the micro-organisms c) cannot remove solid particles and soluble mineralsd) very expensive(requires lots of fuel and energy if it is on a much larger scale)Conclusion: Comparing the 4 water purification methods Method used for water purificationDoes it remove large suspended particles?Does it remove small suspended particles?Does it remove micro-organisms?Does it remove dissolved minerals?SedimentationYesNoNo NoFiltrationYesYesNoNoDistillationYesYesYesYesBoilingNoNoYesNoWater purification in Hong Kong:(by the Water Supplies Department)Source of water in Hong Kongrainwater from reservoirs the Dongjiang water from Mainland ChinaProcess: SedimentationFiltrationfurther water treatmentsSection C: The further water treatment processKilling micro-organismssterilizationChlorinationAdding ozoneUsing ultra-violet light1. Chlorinationa) Chlorine (Cl)toxic chemical(pale green/yellow in colourfind in bleach)pungent smell (smell like the one near the poolside)added to the swimming pool watermay irritate our skin and eyesremove chlorineboiling waterb) Adding ozone(O3)use to clean water for swimmingno taste, colour or smelldoes not irritate our skin and eyescost of an ozone generatorvery highc)Ultra-Violet light(UV light)(purple in colour)used in some drinking fountains in school & water filterc) Fluoridationdoes nothing for the sterilization purposefinal step in water treatmentprevents our teeth for decayingfind in toothpaste Section D.1: Water as a powerful solventSoluble: a substance that dissolves in a liquid soluble solutesInsoluble: a substance that does not dissolves in a liquidinsoluble solutes (iodine & chalk(calcium carbonate): 1. will settle out of the mixture2. found at the bottom of the container as precipitateSuspension: A mixture containing an insoluble solute(X solution)Solvent(Water)+Solute(Sugar)=Solution(Sugar water)aqueous solution(when water is the solvent)Water as solvent in living organisms:Animals: glucosePlants: SucroseSpecial examples:1.Iodinesoluble: alcohol insoluble: water2.Saltsoluble: water insoluble: alcoholClassification between solutions1. Unsaturated solutions:a) have less than the maximum amount of solute dissolved in themb) more solute could be added to the solutionc) the additional solute would still dissolve2. Saturated solutions:a) have the maximum amount of solute dissolved in themb) No more solute can be made to dissolve3. Supersaturated solutions:a) more than the maximum amount of solute dissolved in themb) not normally possiblec) not all substances will form supersaturated solutionsd) formed by heating up saturated solutions & thus adding more solute. Section D.2: Paper chromatography1. Chromatography:a) a powerful technique for separating and analysing small amount of mixturesb) The mobile phase (a liquid or a gas, a suitable liquid solvent or mixture of solvents) flows through the stationary phase (a solid or a liquid supported on a solid, e.g. a very uniform absorbent paper)2. Interpreting the data:a) Rf value of each spot should be calculated b) stands for “ratio of fronts”c) characteristic for any given compoundd) unique for every substancessubstances move with different speedsseparate from one anothere) known Rf values can be compared to those of unknown substances to aid in their identifications.f) Rf=Distance from start to centre of substance spot Distance from start to solvent frontg) often depend on temperature, solvent & type of paper usedh) most effective way: spot known substances next to unknown substances on the same chromatogram3. Purity of the samples:a) may be estimated from the chromatogramb) impure sample: develop as 2 or more spots pure sample: show only 1 spotc) 1 spotmay not be purecontains another compound which didnt separate under the conditions of the experiment (not water soluble, e.g. oil marker) d) often determined in conjunction with other techniques (e.g. measuring a samples melting point)4. Factors determining the speed of movement of a componenta) adsorption on the paper: less strongly adsorbedmove fasterb) solubility in the solvent: more solublemove fasterSection E: Crystallization 1. Crystals:a) naturally made solids with regular shapes and unique coloursb) made from cooling hot saturated solutionsthe solvent can no longer hold all the solutecrystals / evaporating water from a saturated solutionless water to dissolve the solutecrystalsc) Process: solvent+ max. amount of solutesaturated solutionheating+ excess solutesupersaturated solutioncooledsaturated solution+ excess solute in the form of crystalcrystallizationd) Formation of large fine crystal: When water evaporates slowly from a saturated solutionFormation of powders: When the cooling process is too quick (e.g. cooling with ice water, running water)e) Examples of crystals:i) quartz (most common crystal on the Earth)ii) ice crystal (snowflake)iii) table saltCh.7 Common Acids and AlkalisSection A: Common Acids and Alkalis1. Another classification of solutionsa) Acid (acidic solutions) (corrosive: will attack & weaken many things including metals, paper, clothing and skin): i) found in industrial products, e.g. household cleansersii) found in natural substances, e.g. plants, animals, in our bodiesiii) can neutralize an alkaliiv) have a pH value lower/less than pH7v) classified into Strong acid-found in industrial products-will burnt our skins -dangerous-usually for industrial usage Name of strong acidFound inHydrochloric acid (Hcl)Stomach in kill germsSulphuric acid (H2SO4)Car batteriesNitric acid (HNO3)Manufacture of explosives & fertilizersWeak acids-found in food & drinks-safe to take in -taste sour-use to preserve & improve the taste of foodsName of the weak acidFound inCitric acidLemons, limes, grapes & other citrus fruitsLactic acidMilk products, e.g. cheese, yoghurtTannic acidTeaAcetic (ethanoic) acidvinegarFormic(methanoic)acid Ant stingsAsco