Plastics and Polymers
Plastics and Polymers Polymers were first made in the early twentieth century and were known as ‘plastics’. Polymers are constructed from much smaller molecules (monomers) that are joined together to form long chains (polymers). The economy and many industrial companies rely on polymers as a vital resource. An advantage of using polymers over natural materials is that polymers can be manufactured very specifically with varying degrees of stiffness, density, heat resistance and electrical conductivity. The study of natural polymers has also led to great advances in medicine and nutrition. Polymers have a great many uses: sheets and films, adhesives, paints and inks and also synthetic fibres and yarns. A very common polymer used widely in modern life is polyethylene (the simplest polymer). When it’s made into bags for supermarkets and other uses, it’s typically flexible and transparent. Its monomer (a single unit that is repeated) is Ethene (C2H4). It can be polymerised into polyethylene that generally contains around 105 Ethene monomers within its structure. The diagram shows the polymerisation of ethane into polyethene/polyethylene. PVC (polyvinylchloride) is another widely used plastic containing Carbon, Hydrogen and Chlorine. Molecules of vinyl chloride combine to make long chain molecules of PVC. This synthetic polymer is quite cheap and easy to mould and is
Outline different methods of separating substances.
Chromatography Chromatography- this is used for separating mixtures of coloured compounds, the mixtures that are used to be separate in chromatography includes liquids like dyes, ink and most commonly colouring agents in food. Chromatography is carried out on a single piece of paper is used where a small sample is placed at the bottom of the paper where it is then placed vertically in a solvent such as water where it soaks up the paper and carries the sample with it, it allows the mixtures to separate at different rates, so it just allows the “industry” to identify the different compounds in the mixture. Distillation- (simple) this is where a liquid is separated from a solution, commonly used to purify water to make it distilled where it is separated from the salty water, it is where the solution is heated up and the water evaporates from the solution, and goes in to a different container where it is firstly cooled and condensed, the salt from the solution cannot be carried so it is left behind, so to sum it up it is the process of “purifying” a substance by the process of heating and cooling. Precipitation- it is when a transition metal compound is mixed with a sodium hydroxide solution which leads to a displacement reaction, since sodium is more reactive then transitional metals so it takes over the transition metal place/position from the compound, the substance
Titration - Preparation,Neutralisation and Applications in Industry
Preparation of the Standard Sodium Hydroxide solution. P2. Aim: To make an accurate Sodium Hydroxide solution ready for titration. Apparatus: Sodium Hydroxide pellets, Pipette, Distilled water, Volumetric Flask, Spatula, Weighing scale, Goggles. NaOH: 23+16+1=40g. 40g NaOH in 1 litre (1000ml) 10g in 250ml 1g in 250ml 0.1 molar Method: Firstly we weighed out exactly 1 gram of the Sodium Hydroxide pellets ensuring accuracy to its highest to prevent any flaws in our results. We then carefully put the pellets into a volumetric flask. After that we poured approximately 100ml of distilled water into it and shook the solution for approximately a minute till the pellets were fully dissolved. Then we added approximately 150ml of water to make it 250ml we used the meniscus to maintain accuracy by
Column chromatography is a larger scale of thin layer chromatography.
Column chromatography is a larger scale of thin layer chromatography. In this case, the dye mixture- a two coloured compound- was added into the column. The separation of the two different colours began as a mobile phase- mixture of 50% ethanol and 50%water- was run through the stationary phase (alumina- Al2O3). The whole separation process depends on the polarity of the stationary phase, the mobile phase and the compounds composing the dye mixture. The compounds have their own equilibrium between being adsorbed onto the alumina and being soluble in the water-ethanol mixture; the most soluble or least adsorbed compounds travel fast down the column and hence could be separated from the other coloured compound. This could be explained through intermolecular forces; the alumina will form more hydrogen bonds compared to Van der Waals forces with the strongly polar compound. The hydrogen bonds form between the “highly electronegative oxygen atoms in Alumina” and the hydrogen atoms in the compounds. Whereas, the less polar compound will dissolve more in the water-ethanol mixture; and form less hydrogen bonds with the alumina compared to the number of Van der Waals forces that will also form. The compound which is adsorbed more will not travel as further as the compound with lower polarity. The compound with lower polarity will travel in the mobile phase, further down the
Primary and Secondary Standard solutions in chemistry (titration & colorimetry)
Primary standards, such as potassium hydrogen phthalate (KHP) (C8H5KO4), display unique characteristics such as high purity, maintain stability during storage within a long period of time whether in solid or liquid form, large molar mass as calculated to be 204 (RMM), low reactivity with the surrounding air, high stoichiometry and low hygroscopicity (property of absorbing water from its surroundings), which makes them ideal in making precise assessments of the unknown concentration of a known chemical. Secondary standards such as sodium hydroxide (NaOH) do not have the properties listed above, therefore it is low in purity, it is highly liable in absorbing the water molecules (H2O) from the atmosphere, it has high reactivity, it’s concentration changes over time, has lower molar mass known to be 40 (RMM). They are used in standardisations by comparing against primary standards. Primary standards are high in purity; whereas secondary standards have a low purity. Primary standards such as potassium hydrogen phthalate (C8H5KO4) remain stable when stored and the concentration does not alter over time whether it is in solid form or liquid form; however, secondary standards, for e.g. sodium hydroxide (NaOH), does not remain stable and the concentration changes rapidly over time. The primary standard, potassium hydrogen phthalate for example, has a higher molar mass (204 RMM)
Comparing High Pressure Liquid Chromatography and Gas Chromatography
Comparing High Pressure Liquid Chromatography and Gas Chromatography HPLC and GC have different approaches to separating components in mixtures. HPLC deals with separating particularly non-volatile and liquid substances such as ions, polymers and other complex structured molecules into their components; whereas, GC deals with volatile and gaseous substances or the substances could be vaporised (organic or inorganic molecules such as alcohols) while they are in the injection unit. In HPLC high pressures are given from a pump in order to force the mobile phase through the column and interact with the components within the mixture. This is because compounds that react very slowly due to their complex structure are being separated within the column. A vacuum degasser is also present in HPLC and it removes the air bubbles that are in the mobile phase; otherwise these air bubbles will give false peaks in the chromatogram. On the other hand, Gas Chromatography, highly volatile substances such as alcohols are being separated in a mixture, therefore a very high pressure is not necessary because in GC the components are volatile and they do not have to be forced to interact with the mobile phase and the stationary phase because the components themselves are reactive; instead components travel through the stationary phase with capillary action. Heat is being used instead in GC to turn
Qualititive Inorganic Analysis Using the Flame Test.
. State what ‘qualitative inorganic analysis’ means. This technique used in analytical chemistry aims to identify the elemental composition of inorganic compounds. Its focus is mainly on the detection of ions in an aqueous solution. Even when substances are in other forms, they are brought into the aqueous state if necessary, before the use of these standard methods. The aqueous solution is mixed with different reagents in order to test for reactions that are characteristic of certain ions. These reactions may cause solid formation, change in colour and other visual changes. . Identify and explain the errors for your analysis. Nickel wire contamination: The nickel wire which is used in introducing the chemical with the blue flame given out of the Bunsen burner could get contaminated if it is not changed constantly through the stages of different chemicals being used. The chemical that was being used in the first flame test could stick on the wire and when it is used with another chemical it will give the wrong inference. Other factors that could affect the contamination might be dirt particles on the surface that could stick on the wire if it is left on an unclean surface. Misreading Inferences: There are many misreading’s of inferences that could be done overall. The appearance of the chemical could change in colour over time; this will directly lead onto
Testing Nickel (II) Sulphate, Iron (III) Chloride, Potassium Sulphate
. Nickel (II) Sulphate (NiSO4) Iron (III) Chloride (FeCl3) Potassium Sulphate (K2SO4) . Describe the bonding present in the molecule. The bonding present in all three molecules is ‘Ionic bonding’. This type of bonding occurs when a positively charged (cation) and a negatively charged (anion) ion are attracted. It typically occurs between a metal and a non-metal. The bond’s structure is strong and rigid. Nickel (II) Sulphate: Nickel (II) (Ni+2) is the cation, whereas Sulphate (SO4-2) is the polyatomic anion. Iron (III) Chloride: Iron (III) (Fe+3) is the cation, whereas Chloride (Cl-1) is the anion. Potassium Sulphate: Potassium (K+), whereas Sulphate (SO4-2) is the polyatomic anion. . Explain how the cation tests work, use equations. -Appearance: The elements of group 1, 2 and 3 appear to be white whereas, transition metals appear coloured. Potassium is a group 1 element; therefore, its colour is white. This is because group 1 elements do not possess a d orbital that the electrons can move between by absorbing light and allowing various colours to be observed. Transition metals have at least one stable ion that contain d orbitals which are incompletely filled with electrons. Their colours vary on the metal ion charge and the number of ligands (groups of atoms) which are attached to them. For example, Nickel appears to be green with a charge of +2. Iron appears
AQA As Applied Science Unit 3. Colorimetry experiment on Ribena juices
Colorimetry Aim: * The aim behind this science is to measure colours and to predominantly quantify the colour of light sources or objects from visual colour matches. (This means that the eye(s) are used as a tool to identify if the colour is identical or not. Scenario: I am a scientist, my first task is to go into a laboratory and test the concentrations of different Ribena juices, then I am going to find out the unknown dilutions for both Tesco and Asda Ribenas. Hypothesis: The more expensive the higher quality it will be therefore the stronger the concentration of the drink. The cheaper the Ribena juice the lower quality it will be therefore a weaker concentration of the drink. Scientific Background: A specific solution will be used to measure and determine the absorbance of particular wavelengths of light by a specific solution. This is the procedure is used to measure the amount of light something absorbs, this is then measured in units of absorbance, this is also directly proportional to its concentration, this method is used to determine concentration. Colorimetry is also the technology and science used to quantify and describe the human colour perception. What is colorimetry used for? Colorimetry is used in most industries such as: * Food * Paint manufacturing * Colour printing * Textile manufacturing * Chemistry ASDA Equipment: * Ribena *
Anion Test- Testing for negative ions in solutions.. Applied science unit 3 (AQA)
Anion Test- Testing for negative ions in solutions. Equipment: * Pipette * Test tube * Test tube rack * Goggles * Chemicals: Chloride, Sulphate, Carbonate, Dilute nitric acid, Silver nitrate solution, Hydrochloric acid, Barium chloride solution Hypothesis: I will test unknown solutions to find out if they are a Sulphate, Carbonate and Chloride. I would check for the negative ions in order to check for substance present. Method: To start, first of all I would design a results table to record my results in during the experiment, then I would put on my goggles this is to ensure my safety whilst handling hazardous/dangerous substances such as Chlorides. Then I would collect the correct equipment needed for this experiment this includes collecting test tubes, chemicals etc. When I have collected my equipment then I would set it all up such as putting my test tubes in the test tube holder, I would use a pipette to get the chemicals and put them in the test tube for testing. Then I would start the experiment and doing the tests, for example if I was to test for a Chloride I would first add a few drops of dilute Nitric acid then add a few drops Silver nitrate solution. The results that I get I would then record them in my results table. Risk Assessment: Name of hazard Hazard Safety Precautions Emergency action Risk level (Low/Medium/High) Image Pipette Pipettes
