Integrated Science Module

Chemistry
1. Separation Techniques
  1. Obtaining Pure Substances from Mixtures
    1. 1. A mixture is made up of two or more substances that are not chemically combined. 2. A pure substance is made up of one single element of compound and is not mixed with any substance. 3. To decide which method to use in order to separate a mixture into pure samples, or remove impurities, we must look at the properties of each substance.
  2. Separating a Solid from a Liquid: depends on whether the solid is soluble in the liquid
    1. Filtration: used to separate insoluble solid particles from a liquid (e.g. sand, clay, dust from water)
      1. Process: 1. Pour mixture into filter tunnel lined with filter paper 2. Collect filtrate (water) that pass through the paper 3. Collect residue and dry on a piece of filter paper
        Filtration works because of difference in particle size; the smaller liquid particles are able to pass through the pores of the filter paper and become the filtrate, while the insoluble solid particles are larger and unable to fit through so they are trapped by the filter paper and become residue.
    2. Evaporation to dryness: used to separate soluble solids from a liquid/solution
      1. Process: Heat solution until all the water has boiled off
        The solid obtained through evaporation to dryness may not be a pure sample as any soluble impurities will stick to the solid once the water has boiled off
    3. Crystallisation: used to obtain a pure solid sample from a solution (since Evaporation to Dryness may not obtain pure samples); works well with substances that decompose on strong heating
      1. Process: A solution is heated until it becomes a saturated solution (or a solution in which no more solute can dissolve). By then allowing it to cool, the amount of solute that the solvent can hold is then lowered, forcing some amount of solute to form pure crystals. (the solvent must not be allowed to boil!)
        Crystallisation works because the the solubility of the solute changes (increases) as the temperature changes (increases).
        Fast cooling results in a large number of small crystals because the crystals don't have time to form, but slow cooling allows the crystals to grow larger and results in a small number of large crystals.
  3. Separating Solids from Solids
    1. Using a suitable solvent: choosing a solvent in which only one solute in the mixture is soluble
      1. Process: Add solvent to dissolve solutes, filter mixture, and evaporate filtrate to dryness -- Chapters 6 & 7: solubility of different compounds
    2. Sublimation: using sublimation to separate a solute which sublimes from another solute in the mixture which is stable to heat
      1. Process: Heat the mixture and allow one substance to sublime and enter a gaseous state; place a cool surface above to collect the sublimed substance and allow it to condense to return to a solid state.
    3. Magnetic attraction: can be used to separate a magnetic substance from a non-magnetic one
  4. Separating Liquids from Solids
    1. Simple distillation: used to obtain a pure solvent from a solution
      1. Process: Boil the solution in a distillation flask; the water to vaporises, rises and enters the condenser. A thermometer is usually suspended at the side arm of the flask to measure the boiling point of the substance being distilled and should not be dipped into the solution itself. The water vapour of the boiled solvent is cooled and condenses in the condenser (liquid usually enters the condenser from the bottom so the cooling liquid can only escape if the outer water jacket is full). The pure liquid form of the solvent is then collected as a distillate in the receiver; as the distillation process continues, the remaining solution in the flask becomes more and more concentrated until it finally becomes a solid residue.
        Simple distillation only works because the solvent has a lower boiling point than the solute
  5. Separating Liquids: depends on whether or not the liquids are miscible (can mix with each other)
    1. Using a Separate Funnel: used to separate immiscible liquids
      1. Process: the mixture is poured into a separating funnel supported by a report stand; the liquids are then allowed to separate completely (the denser liquid sinks and two distinct layers are formed) before the funnel tap is opened to let the bottom layer drained out
    2. Fractional Distillation: used to separate miscible liquids with significantly different boiling points
      1. Process: A fractional column filled with beads and attached to a condenser is attached to a round-bottomed flash filled with the mixture e.g. ethanol and water. When the solution is heated, the 2 liquids rise up as vapour; because the condensation point of a liquid is the same as its boiling point, the liquid with a higher boiling point only needs to cool down a little bit to reach its condensation point; because the temperature is higher toward the bottom of the flask, the liquid with a higher boiling point condenses first. The ethanol which has a lower boiling point rises to the top and condenses through the condenser before falling into the receiver, before allowing the water to reach its boiling point at the top and condense in its turn
        Fractional distillation can be used to obtain ethanol produced by the fermentation of glucose solution
    3. Chromatography: used to separate two or more solutes which dissolve in the same solvent
      1. Process: A line is drawn with a pencil 1cm away from the bottom of the paper at a drop of the solution is dropped on the line. The paper is then dipped into a glass tank containing the solvent and the paper soaks it up, dissolving the dyes while travelling up the paper, carrying them along. The more soluble the dye, the further it will move up.
        Chromatography works because of the different solubilities of the solutes, and because of the presence of a mobile phase (solvent), a stationary phase (the paper) and adsorption (the interaction of the solute particles with the stationary phase)
        Interpreting the Chromatogram: 1. Pure substances give only one spot on the chromatogram, while a mixture gives several coloured spots of separated dye. 2. Rf values (retention factor) = the distance travelled by the substance/distance travelled by the solvent (measured from pencil line to solvent front) 3. Samples are analysed to identify the components present in them since the same dyes produce the same coloured spots at the same height e.g. Governments used chromatography to find out the substances contained in certain food dyes to make sure they are safe for consumption
        A locating agent is sprayed on the chromatogram to cause colourless substances to show up as coloured spots so that we can calculate their Rf value and identify them
  6. Determining purity: helps us detect harmful impurities and ensure that products meet quality standards
    1. A solid is pure if it has an exact and constant melting point, and it melts completely at that point
      1. Impurities lower the melting point of a solid (only if they are soluble!) because foreign substances disturb the forces which hold the solid particles together, and so a smaller amount of kinetic energy in the form of heat is needed to overcome these forces and cause the liquid to melt
      2. Impurities cause the solid to melt over a range of temperatures. The disruption of the forces holding the solid particles together, caused by the contaminants, causes the molecules closes to the impurities to melt first, at a lower temperature, while the rest of the structure melts nearer to the normal melting point
    2. A liquid is pure if it has an exact and constant boiling point.
      1. The mobile particles in the liquid state rearrange themselves around the impurities to gain maximum attraction and stability, thus even more energy in the form of heat is required to break these bonds and cause the liquid to enter a gaseous state; impurities also cause the boiling to take place over a rage of temperatures
2. Kinetic Particle Theory: States of Matter & Physical Change
  1. States of Matter: the 3 states of matter are solids, liquids and gas
    1. Solids: fixed volume, fixed shape; cannot be compressed
      1. the particles in a solid are held together in a neat orderly fashion by extremely strong forces of attraction which prevent them from moving around freely; they only have enough kinetic energy to vibrate/rotate in their places. Since the particles are already close together, they cannot be compressed any further.
    2. Liquids: fixed volume, no fixed shape, cannot be compressed
      1. the particles in a liquid are held together in a disorderly manner by weaker forces of attraction than in a solid, which allows them to move around freely; they have more kinetic energy and are not held in their places, giving them no fixed shape. However the particles in a solid are still relatively close to each other and thus cannot be compressed as well.
    3. Gases: no fixed volume, no fixed shape, can be compressed
      1. the particles in a gas are spread far apart as the forces of attraction between them are even weaker than those of a liquid, allowing them to move around rapidly in any direction, thus they have no fixed shape. They have a lot of kinetic energy and are not fixed in their places. Because there is a lot of space between the gas particles, they can be forced together, hence gases can be compressed
  2. The Kinetic Particle Theory states that all matter is made up of tiny particles in constant random motion; this theory can be used to explain/describe the different states of matter & their property differences, as well as the physical changes that place within them.
  3. Physical Change: when matter is heated or cooled, kinetic energy is taken out/given in in the form of kinetic energy, causing the particles to lose/gain kinetic energy, and thus change in state (solid = least energy, gas = most energy); does not produce new substances, involves changes in state and dissolving
    1. Melting: solid to liquid
      1. Heat energy is absorbed by the solid particles and is converted into kinetic energy; during this time, the temperature of the solid rises. The kinetic energy gained by the solid is used to overcome the strong forces of attraction between its particles, during which the temperature plateaus. The particles are now closely packed in a random manner and can move freely about the liquid; the temperature continues rising.
    2. Freezing: liquid to solid
      1. When the liquid is cooled, it loses kinetic energy in the form of heat, during which the temperature decreases. When it reaches the freezing point, the particles begin settling in their fixed positions and forming bonds of attraction; they can now only vibrate in their fixed positions. Here the temperature remains the same. When the liquid has become a solid, its temperature continues to drop.
    3. Boiling: Liquid to gas
      1. The liquid absorbs kinetic energy in the form of heat, during which the temperature rises. When the boiling point is reached, this kinetic energy is used to overcome the forces of attraction between the particles, and the temperature plateaus. Finally, the particles have enough energy to move around rapidly in any direction, and are spaced far apart, and the temperature continues rising as they gain kinetic energy.
    4. Evaporation: liquid to gas
      1. The process of evaporation is similar to that of boiling, however it happens at temperatures below boiling point and takes place more slowly. This is because only the liquid particles on the surface are closer to the heat source and gain enough kinetic energy to enter the gaseous state
    5. Condensation: gas to liquid
      1. When gas comes into contact with a cool surface, it loses kinetic energy in the form of heat, and gains forces of attraction which cause it to be packed together in a non-orderly manner like in a liquid. The loss in kinetic energy means it can only move about freely instead of rapidly in any direction.
    6. Sublimation: solid to gas
      1. When a solid goes past its melting/freezing point, the particles on the surface gain enough energy to overcome the forces of attraction and immediately start moving around rapidly in any direction; they have now entered the gaseous state
    7. Diffusion: the movement of particles from a region of higher concentration to a region of lower concentration; proves the KPT (that matter is made up of small particles in constant random motion)
      1. In gases, the gas particles which are moving around rapidly in any direction move into the spaces between the air particles around them. In liquids, liquid particles which can move freely about the liquid move (diffuse) into the spaces between the liquid particles as well
      2. Gases with a lower molecular mass (lower mass of each particle) diffuse/move faster than those with a higher molecular mass
      3. The higher the temperature (of the surroundings), the higher the rate of diffusion; since heat travels from a hotter area to a colder area, when placed in an environment with a higher temperature, the substances gain more kinetic energy in a shorter amount of time, which enables them to move and thus diffuse faster.
Physics
1. Measurement and density
  1. Physical Quantities: a quantity that can be measured and has an SI unit and numerical magnitude
    1. Base Quantities (and SI units): Length, metre, m; Mass, kilogram, kg; Time, second, s; temperature, kelvin, K
  2. Prefixes: easier to express extremely large/small physical quantities -- 10^12: tera, 10^9: giga, 10^6: mega, 10^3: kilo, 10^-1: deci, 10^-2: centi, 10^-3: milli, 10^-6: micro, 10^-9: nano, 10^-12: pico
  3. Measurement of Length: precision is the smallest unit an instrument can measure; often when we are not careful in our readings parallax errors may result
    1. Metre ruler: lengths of up to one metre
      1. Steel tape: lengths over a metre
        Cloth tape: measurements over a curved surface
      2. Vernier Callipers: precision of 0.01cm/0.1mm; reading on the main scale is done to 0.1cm/1mm -- read the one to the left of the zero, reading on vernier scale is to 0.01cm/0.1mm -- read the mark which coincides with the main scale
        Positive zero error: vernier scale 0 is right of main scale 0; count zero error from the left and minus the error later; Negative zero error: vernier scale 0 is left of main scale 0, count 0 error from the right and add the error later
        Micrometer screw gauge: precision of 0.01mm/0.001cm; read the main scale immediately left of the thimble -- to 0.1mm, then read the line aligned with the centre line on the thimble -- to 0.01mm
        Positive zero error: zero below the datum line; negative zero error: zero above the datum line
  4. Measurement of Time: can be done using stopwatches, clocks or pendulum; period is the time it takes the pendulum to go through a to and fro movement to return to its original position
  5. Precision vs. Accuracy: precision is two measurements getting as close to each other as possible, and accuracy is a measurement getting as close to the known value as possible
  6. Density: mass/volume; denser objects sink, less dense objects float
2. Sound
  1. What is sound?: Sound is a form of energy that is transferred from one point to another in the form of a longitudinal wave which travels in the same direction as a vibrating source placed in a medium; waves transfer energy and not matter!
    1. Sound waves travel at different speeds in different mediums -- they travel the fastest in solids and the slowest in air because solid particles are the closest together so they pass energy to each other more quickly
  2. Characteristics of Sound Waves
    1. The vibrating sources displaces the medium particles around it, causing sound waves to propagate (spread) in a series of compressions (regions of higher air pressure) and rarefactions (regions of lower air pressure)
    2. Wavelength: the distance between the centres of two consecutive compressions/rarefactions
    3. Period: the time it takes for one rarefaction and one compression (one cycle)
    4. Frequency: the number of cycles in a given unit of time; number of cycles in a second is Hertz (Hz) -- the higher the frequency, the higher the pitch; frequency is calculated as 1/period
      1. Amplitude: a wave particles maximum disturbance from its undisturbed position; the larger the amplitude the louder the sound
  3. Uses of Sound -- Echoes
    1. Echoes are the repetition of a sound due to the reflection of sound, which happens when it is reflected off a hard and flat surface
      1. Can be used for measuring distances/locating objects by taking note of the time interval before the reflected signal and using the speed of sound to work out the distance
3. Thermal Transfer & Temperature
  1. Measuring Temperature
    1. Temperature: how hot or cold and object is Heat: the amount of thermal energy being transferred from a hotter to a colder region
    2. Measured with thermometric substances which have physical properties -- known as thermometric properties -- which vary continuously and linearly with temperature
      1. Mercury-/Alcohol-in-glass thermometers contain mercury/alcohol which have fixed masses but volumes that vary with temperature
      2. Electrical voltage or electromotive force is used in a thermocouple thermometer (which have two junctions placed in different temperatures to figure out the corresponding temperature for each voltage; then one junction is placed into a cold junction and the other junction is used to measure and the voltage shown tells us the temperature)
  2. Thermal Energy Transfer
    1. On a molecular level...when the temperature increases, the average kinetic energy of the molecules increase, causing them to move faster and change direction more quickly
    2. Conduction: the transfer of thermal energy through a medium without any flow of the medium; happens when particles gain kinetic energy through the gain of thermal energy and collide with their neighbours, making them vibrate, and happens faster in metals because more thermal energy is transferred via the motion of free electrons; works worst in liquids and gases because the molecules are spaced further apart, making the collision process slower
      1. Convection: the transfer of thermal energy through the convection currents in a fluid (e.g. liquids or gas) due to differences in density; when the liquid is heated at the bottom, it expands in volume, causing it to decrease in density and therefore rise. The upper region is cooler in comparison, and has a higher density, thus it sinks
        Radiation: the transfer of thermal energy in the form of electromagnetic waves e.g. infrared radiation without the aid of a medium -- good emitters are good absorbers, and both are different from conductors. Dull and black surfaces are better emitters/absorbers, object's with higher surface temperature are better emitters, and objects with larger surface areas are better emitters/absorbers
    3. Practical uses
      1. Good Conductors can be used for cooking utensils, soldering irons, or heat exchanges in laundromats to heat clean water to an ideal temperature for washing
        Bad conductors can be used as table mats, utensil handles, warm clothing, double-glazed windows and sawdust
        Convection is used to help heat electric kettles, help the air-conditioner cool the room, and in household water systems which help push cold toilet water down and bring hot bathing water up??
        Radiation can be used in greenhouses or to design vacuum flasks to minimise heat loss through radiation/conduction/convection
Biology
1. Organisms and their Environment
  1. Food Chains & Food Webs
    1. Food Chains: shows the energy flow within a particular ecosystem
      1. Sun: initial energy source for most communities of living things
        Consumers: eat other organisms to obtain their nutrients; primary consumer eats producer, secondary consumer eats primary consumer, tertiary consumer eats secondary consumer
        Decomposers: organisms that feed on dead or decaying matter/animal faeces and break them down into simpler material to be absorbed by the soil, thus returning the nutrients from dead organisms to the soil where they can utilised by producers
        Decomposers break down substances through decomposition (a chemical process) in order to gain their nutrients, while Detritivores simply feed on these dead/decaying matter
        Heterotrophs: cannot synthesise their own food and have to rely on other organisms for nutrients aka consumers
        Trophic level: the position of an organism in a food chain, food web or pyramid
      2. Producers: organisms which make their own food/obtain their own nutrients; usually green plants which utilise photosynthesis, the process of harnessing the Sun's nergy in order to produce food
        Autotrophs: can produce their own food from the substances in their surroundings aka producers
    2. Food Web: network of interconnected food chains
    3. Energy transfer: only 10 percent of energy is passed on to the next trophic level, as the rest is used for life processes like movement and digestion, for heat energy and passed as faeces to decomposers; because of the energy loss there is seldom more than 5 trophic levels in a food chain
    4. Because sunlight is converted into heat or chemical energy and lost to the environment in that way, the energy in an ecosystem is non-cyclical (does not return to its origin)
    5. The Carbon Cycle: Carbon dioxide is used to create chemical energy by plants through photosynthesis; when animals or other organisms eat these plants, the carbon is passed to them; when microorganisms feed on the waste material of these animals the carbon is passed to them as well. Carbon is then released back into the atmosphere through respiration or decomposition or decay; in this way carbon too is a non-cyclical
  2. Characteristics of an Ecosystem
    1. Biotic: living things e.g. producers, carnivores, herbivores, omnivores, detritivores
      1. Abiotic: sunlight, water, soil, temperature, precipitation
  3. Relationships within an Ecosystem
    1. Symbiotic
      1. Commensalism: one species benefits and the other is unaffected e.g. a bird and a tree
        Mutualism: both species beneftit
        Parasitism: one species benefits while the other is at a disadvantage (but generally doesn't die)
    2. Oppositional
      1. Predation: one species feeding on and killing the other species
      2. Competition: two species fighting for the same resources; may or may not include direct interference with each other e.g. two plant roots fighting for water in the soil
  4. Pyramids of Numbers & Biomass
    1. Pyramid of Numbers: shows the population numbers at each stage of the food chain; as energy is lost to the surroundings from one trophic level to the next, there is increasingly less amount of energy to support the next trophic level and thus the number of organisms decreases as the trophic level increases
      1. The shape of the 'pyramid' may vary; sometimes the producer is a large plant like a tree which can support many primary consumers, supposing the primary consumers are all small animals such as insects; in this case there is a narrow base.
    2. Pyramid of Biomass: shows the dry mass of the organisms at each trophic level; as it decreases from one trophic level to the next, the pyramid always gets narrower to the top -- the dry mass always decreases because since energy is lost from one trophic level to the next, logically there would have to be more of one organism than the organisms on the next level in order for their energy needs to be met
2. Cell Structure & Organisation
  1. Movements across cell membranes
    1. Osmosis: the diffusion of water particles from an area of higher concentration to an area of lower concentration through a partially permeable membrane
      1. In a solution with higher solute concentration (lower water potential)
        Plant Cells: water leaves the cell through osmosis, causing the cytoplasm to shrink away from the cell wall (apparently it is the vacuole that shrinks in volume?) and the cell to become flaccid; the plant wilts and is unable to absorb sunlight
        Animal Cells: cells lose water through osmosis and shrink, becoming wrinkled/crenated; this does not happen inside our bodies because the kidney carries out osmoregulation to ensure our blood has the same concentration as our cells
      2. In a solution with a lower solute concentration and higher water potential
        Plant cells: water enters the cells through osmosis, causing the cytoplasm to push against the strong cellulose cell wall, which prevents it from bursting and causes the cell to become turgid, allowing the plant to stand upright and absorb sunlight for photosynthesis.
        Animal Cells: when animal cells gain water through osmosis, they swell and burst (or lyse) as they have no strong cel walls to prevent them from doing so)
    2. Diffusion: particles move from an area of higher concentration to an area of lower concentration; particles have to be free to move, thus diffusion does not occur in solids
      1. Diffusion allows inhaled air to diffuse from the region of higher concentration within the alveoli to the region of lower concentration in the blood circulating through the lungs/oxygen from arteries to the tissues
        Causes digested food molecules to diffuse from the small intestine to the capillaries within the villi
    3. Concentration gradients: solution with a low solute concentration has a high water concentration and high water potential, and vice versa
  2. Multicellular and Unicellular Organisms
  3. Surface Area to Volume Ratio: cells have to interact with their environment in order to survive -- absorbing gases and food molecules and eliminating waste products -- and the amount of interaction depends on their surface area. The bigger a cell gets, the smaller its SA:V, meaning the amount of materials it can pass to the interior is smaller. IT cannot get too big otherwise it will be unable to survive!
    1. Red blood cells: the main function of the red blood cell is to transport oxygen from the body cells and bring carbon dioxide to the lungs; its biconcave shape gives it a larger SA:V and allows more oxygen/CO2 to diffuse in and out of it more quickly
      1. Root hair cells: large surface area of the cells gives it a large SA:V and allows it to absorb more water and mineral nutrients from the soil and transport it to the plant
        Small intestine: the small intestine is covered in folds known as villi, which give it a larger surface area and thus a larger SA:V, allowing it to absorb more nutrients for the body
  4. Cell size: cytoplasm, cell wall/membrane (regulates movement of substances in and out of the cell), nucleus (controls all activities of the cell and contains genetic material), chloroplasts (contains chloroplasts, which absorb light energy to go through photosynthesis), mitochondria (produces ATP through respiration), vacuole
3. Transport System in Living Things
  1. Blood Vessels
    1. Arteries: carry blood away from the heart towards an organ e.g. Aorta: heart to rest of the body, to liver: hepatic artery, to kidney: renal artery, to lungs: pulmonary
      1. Arteries have thick, muscular walls; because the walls are thick, the inner passageway is smaller, which increases blood pressure. They transport oxygenated blood with the exception of the pulmonary artery which transport deoxygenated blood from the heart to the lungs; the blood is under high pressure
    2. Veins: carry blood from an organ towards the heart e.g. Rest of the body to the heart: vena cava, lungs to heart: pulmonary, kidney to heart: renal, liver to heart: hepatic
      1. Veins have thin walls in comparison and a wider passage, thus the blood they carry has a lower pressure. They always carry deoxygenated blood with the exception of the pulmonary vein that carries blood from the lungs to the heart. Veins also have valves to prevent back flow of blood. The valves look like an arrowhead which point in the direction of bloodflow
    3. Capillaries: have narrow thin walls (as opposed to veins which have wide thin walls giving it a large lumen) and low blood pressure. Gas exchange happens here -- oxygen passes through the walls to the muscle/tissue, and CO2 passes from the tissues to the blood
  2. Blood
    1. Plasma: liquid which makes up most of the volume of blood; helps transport carbon dioxide, digested food, waste materials
    2. Platelets: help in blood clotting
    3. White blood cells: ingest pathogens (disease causing microorganisms) and produce antibodies (which attach themselves to foreign particles or microorganisms destroying them/rendering them immobile or unable to penetrate cell walls, thus preventing us from contracting diseases)
    4. Red blood cells: helps transport oxygen
  3. Heart
    1. Left Side: blood enters the left atrium through the pulmonary vein, and extis the left ventricle through the aorta; has thicker walls because it needs to put the blood under higher pressure for it to be pumped through the entire body
    2. Right Side: blood enters the right atrium through the pulmonary artery, and exits the right ventricle through the vena cava. Both sides have valves to prevent the back flow of blood
    3. During exercise...the muscles need more energy, so they respire more, requiring more glucose and oxygen, and producing more carbon dioxide and other waste materials, so the heart has to contract faster to meet these demands, increasing heart rate
    4. Fatty plaque may build up in the coronary arteries' walls, narrowing the lumen and cutting off the blood supply to the heart muscles, which might lead to a heart attack

Siguiente

Integrated Science Module

Descripción

Resumen del Recurso

Similar

	Creado por Sam S hace más de 8 años