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GCSE: Classifying Materials
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How to tell if something is ionic
- 1 Ionic compounds have strong electrostatic attractions between their positive and negative ions. These take a lot of energy to break, so will have a very high melting and boiling point.
- 2 Ionic compounds can conduct electricity when dissolved in solution as their ions are free to move and carry charge. When they are solids, however, their ions are held in a fixed lattice so they cannot move and conduct electricity.
- 3 Ionic compounds are soluble in polar solutions like water. They are insoluble in organic solvents like cyclohexane.
- 4 Ionic compounds all form crystal salts. If these are hydrated they will often be brightly coloured. If they are not hydrated they will usually be transparent or white.
- 5 Ionic compounds are made from metal cations bonding to non-metal anions in a giant lattice.
How to tell if something is a giant covalent
- 1 Giant covalent compounds are held together by incredibly strong covalent bonds. These take a lot of energy to break, so will have an incredibly high melting and boiling point.
- 2 Giant covalent compounds do not have anything to carry charge (such as ions or delocalised electrons) so will not conduct electricity. The exception to this rule is graphite, as this has delocalised electrons so can conduct.
- 3 Giant covalent compounds are insoluble in both polar and non-polar solvents. This is because their strong covalent bonds are too strong to be broken by the solvent.
- 4 The three main forms (allotropes) of carbon that are giant covalent compounds are diamond (a beautifully shiny rock), graphite (which looks like the tiles on our roofs) and fullerines. Fullerines have a “football” shape.
- 5 Apart from allotropes of carbon, the most commonly occurring giant covalent compound that crops up in exams is SiO2.
How to tell if something is a simple covalent
- 1 Simple covalent compounds are held together by weak van der Waals forces. These take little energy to break, so have a very low melting and boiling point.
- 2 Simple covalent compounds do not have anything that can carry charge (like ions or delocalised electrons), so they cannot conduct.
- 3 Simple covalent compounds are soluble in non-polar solvents, and insoluble in polar solvents like water.
- 4 Due to their low melting and boiling point, most simple covalent compounds are liquids or gases at room temperature. The halogens will give coloured gases- Cl is pale green, Br is orange, I is an almost black solid which sublimes to a purple gas.
- 5 Simple covalent compounds are made from a non-metal bonding to a non-metal.
Identifying an Ionic Compound. Objectives: To learn and test for metal ions and non-metal ions and then apply them to discover the identity of an unknown ionically bonded substance5 star(s)
Ionic compounds are soluble in water. Charges on ionic compounds (dipole-dipole interactions) attract water molecules. Metals form cations, electron loss forms cations. Group 1= 1 electron in the outershell (Li+1) Group II= 2 electrons in the outershell (Be+2) Group III= 3 electrons in the outershell (Al+3) Nonmetals form anions, electron gain forms anions. Group V= 5 electrons in the outershell, so needs to gain 3 electrons. (N-3) Group VI= 6 electrons in the outershell, so needs to gain 2 electrons.
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These relations can be summarised as: ATOMIC NUMBER = NUMBER OF PROTONS NUMBER OF PROTONS = NUMBER OF ELECTRONS MASS OF ATOM = PROTONS + NEUTRONS Examples: Element Atomic Number Protons Electrons Neutrons Mass Number Na 11 11 11 12 23 C 6 6 6 6 12 U 92 92 92 146 238 Electron Structure The electrons orbit the nucleus in 'shells'. These can hold the following numbers of electrons: The innermost shell can contain up to 2 electrons The next shell can contain up to 8 electrons The next shell can contain up to 8 electrons (although this can be expanded up to 18)
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In this CDA I will write about how plastic bags are made, why plastic bags are so controversial, the benefits and drawbacks of using them, and I will include an experiment that I carried out at school to determine the strongest plastic bag (out of various
Polyethylene is the most widely used plastic that there is. Three polyethylenes are identified as being used in the manufacture of plastic bags because of their density: - Low-density polyethylene, or LDPE - Linear low-density polyethylene, or LLDPE - High-density polyethylene, or HDPE Branching is replacing the polymer chain with other forms or variations of the monomer. It can change the type of the plastic. For thinner plastics, polymers are branched highly. Also, for a plastic bag that is less see through, it needs to be more branched, but also the easier it is to tear.
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Gold. For thousands of years, gold has been regarded as the finest and most precious metal known to man. In this CDA, I will try to find out why gold is so valuable.
This means that it can be used over and over again, and for different purposes, without wearing out or losing colour. Gold only has one stable isotope, which is gold-197 (or ). An isotope is a different type of atoms, where the atomic number (number of protons) is the same, but the number of neutrons is different. Gold doesn't oxidise easily, which means that it doesn't bond with oxygen, as a result of being highly unreactive. It oxidises with nitric acid to Au3+, although to small amounts.
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Our experiment consisted of two samples of water containing unknown substances, and our objective was to identify the compound present in the substance.
This is why in kettles, where water is heated, calcium carbonate forms as scale. Chemical descalers contain a weak acid which reacts with the calcium carbonate. Permanent hardness of water is caused by dissolved calcium sulphate and magnesium sulphate. As you've probably guessed, this type of hardness cannot be removed easily (i.e. boiling). Instead, it has to be removed by chemical treatment. Hardness in all types of water can be removed by distillation. However, this is not a process used in the real world on a large scale. Permanent and temporary hardness can be removed by using washing soda (sodium carbonate crystals).
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However, many restaurateurs rejected Prof Wiseman's suggestion. Mary Ann Gilchrist, head chef of Carlton Riverside, Llanwrtyd Wells, Powys, said she would not be removing salt cellars from her restaurant. She said, "I have read all the information about salt but I still think people should have the right to choose whether they season their food or not, although I do like to see people taste their food first before adding salt. "I hate going into restaurants where there is no salt available on the table.
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In liquids their particles are continually moving at various speeds, which then collide in different ways. There are different ways of collisions occurring which have different effects such as 'head on' and 'glancing' collisions. The particles that contain a lot of kinetic energy (at a high temperature) collide with a large force therefore gain a heavy contact with another particle (head on). This is known to be successful and a reaction takes place. Where as a 'glancing' collision the particles have not got enough kinetic energy (at a low temperature) to produce a reaction because the contact is not great enough, so a reaction will not occur.
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Reactions in which the activation energy is high are very slow at room temperature, because only a very small fraction of collisions have enough energy to overcome the activation energy. The success rate of collisions is low. One of the ways to increase the rate of reaction would be by adding a catalyst, this would enable particles a boundary where they can collide against each other. A use of a suitable catalyst may allow particles to react even if they collide with little energy therefore more successful collisions are likely.
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= Sodium Pb = Lead Ag = Silver Periodic table As early scientist discovered more and more elements they had to think of a way to organise them. Each element was given a name and a number Dmitiri Meneleev a Russian scientist organised a system called the periodic table Scientist today used a modified version of this table The group number is the number of electrons in the outside shell The period number refers to the outermost shell containing electrons The atomic number is the Protons and the neutrons in an atom Inert Gases gasses which don't change or mix Noble gasses which cannot be mixed with other gasses First 20 elements 1.
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I have decided to use 50cm3 of acid, because it is not a great amount and it is an easy number to dilute to the right concentration. Now I need to find out the right quantity of calcium carbonate to use, in order for this investigation to be carried out clearly so that the reaction will not too fast with 2 molar or too slow with 0.4 molar of acid. I am going to do so by carrying out a preliminary test.
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The number of protons gives the atomic number. Protons have a positive electronic charge, while neutrons have none. The electrons that spin around the nucleus, like planets orbiting the Sun, have a negative charge. But electrons are not 'solid b***s', they are bundles of energy that move almost as fast as light. There are always the same numbers of electrons and protons in an atom. number of protons = atomic number of the atom number of electrons = number of protons number of protons + number of neutrons = mass number number of neutrons = mass number - number of
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Number of moles = Mass in g (of element or compound) Mr (of element or compound) Chemical formula: * Calamine: ZnCO3 * Zinc Oxide: ZnO * Carbon dioxide: CO2 These 3 different chemicals all have different Relative Atomic Masses (RAM) this is also known as the mass number, which is a number that says how many different protons and neutrons each chemical has. ZnO + CO2 ZnCO3 (C = 12, O = 16, Zn = 65) But this is not what we need to know we need the Relative Formula Mass (RFM.)
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Each of these concentrations needs to be repeated 3 times Variables In this experiment, the independent variable is the concentration of the hydrochloric acid. I will change this variable so that I may study the effect that different concentrations of acid have on the dependent variable. The dependent variable is the rate of reaction, as the rate at which it occurs will depend on the acid concentration. I will have to keep all of the other variables the same, so that it will be an entirely fair test. I will keep the weight of the marble chips the same.
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A compelling aspect of mass customisation is that it meets diverse objectives. The customer desires uniqueness; freedom of choice; perfect fit or form; fair, competitive cost. The manufactures want to differentiate from their competitors, to improve profit margins and to reduce risk and returns. Retailers want to sell products at higher profit margins, to provide product variety and choice for the customer and to minimise the inventory risk. Today's customer for mass customisation tends to address the desires of more affluent people, those, for example, who can afford a custom-built yacht, expensive vehicle or a special item of clothing, but that situation is changing fast.
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To conjecture the structure and bonding of eight unknown solids by analysis of experimentally determined properties.
Solubility Aim of section "To test the solubility of each of the eight unknown solids in both polar and non-polar solvents to aid in the identification of each substance as polar or non-polar and hence to assist in the determination of structure and bonding" METHOD1 - Using the polar solvent: [distilled] Water (H2O) * Fill 100ml beaker with 50ml distilled water * Carefully add small quantity of unknown substance with spatula * Stir vigorously for up to 2 minutes (or until substance dissolves)
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two: 25ml HCl and 10g CaCO3 Time in seconds Weight in grams 0.00 128.21 0.15 128.18 0.30 128.15 0.45 128.14 1:00 128.14 1:15 128.12 1:30 128.11 1:45 128.11 2:00 128.11 2:15 128.11 2:30 128.10 Experiment 3: 40ml HCl and 5g Ca C03 Time in seconds Weight in grams 0.00 50.73 0.15 50.68 0.30 60.67 0.45 50.66 1:00 50.64 1:15 50.64 1:30 50.64 1:45 50.63 2:00 50.62 2:15 50.62 2:30 50.62 Prediction: In the preliminary work I only used one sample so I cannot predict which of the two samples will be purer.
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An exothermic reaction is one, which gives out energy to the surroundings usually in the form of heat and is shown by a rise in temperature. This is because, during a chemical reaction old bonds are broken and new bonds are formed; the bonds between the copper and sulphur are broken and a new bond is formed, iron sulphate. Energy must be supplied to break the existing bonds, therefore the breaking of bonds is an endothermic reaction and energy is released when the new bonds are formed, therefore the forming of bonds is an exothermic process.
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An experiment to investigate the factors that determine the amount of energy released when alcohols are burned.
Again, different types of alcohols can be formed due to the different number of carbon atoms in a chain. This gives us methanol and ethanol: When the number of carbons in a chain becomes more than two, the OH molecule can substitute either a hydrogen atom on the first carbon atom in a chain or indeed on any of the carbon atoms in the middle of the chain. This gives variations of molecules that have the same number of different atoms (isomers). This gives us propan-1-ol and propan-2-ol: Propan-1-ol Propan-2-ol When we reach alcohols with a larger number of carbon atoms, such as septanol, there are a lot more different isomers such as septan-1-ol, septan-2-ol, septan-3-ol and even septan-4-ol, since there are a lot of different places where the OH molecule can form a bond.
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In short, light photons falling on transition element compounds interacts with the d-electrons, exciting them and causing electron transitions. Some of the wavelengths in the light are absorbed leaving the complementary colours to be seen. In our case we are using potassium chromate indicator- here the chromium is the transition metal. The equipment necessary for a titration are illustrated below: A: Conical flask- this is the reaction vessel B: Burette- a graduated tube with a tap and is used to deliver the standard solution into the reaction vessel C: pipette-filled by suction, it is used to transfer a known volume of the solution to be analysed into the flask D: pipette safety filler and is the suction device used
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Ions Ionic compounds are those which occur as one element loses electrons and the other one gains them, for example, lithium + fluorine --> lithium fluoride. This is shown as below: 1+ Sodium Potassium Lithium Silver Hydrogen Na + K + Li + Ag + H + 1- Fluoride Chloride Bromide Hydroxide Nitrate F - Cl - Br - OH - NO3 - 2+ Magnesium Calcium Copper Zinc Lead Barium Iron (II) Mg 2+ Ca 2+ Cu 2+ Zn 2+ Pb 2+ Ba 2+ Fe 2+ 2- Oxide Carbonate Sulphate O 2- CO3 2- SO4 2- 3+ Aluminium Iron (III)
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potassium Iron Fe Decreases and sodium, and the least reactive are Lead Pb found at the bottom, i.e. Mercury and Copper Cu Gold. Silver Ag Mercury Hg Gold Au The reaction between zinc and copper can be described as a displacement reaction because zinc is more reactive than copper, and so it displaces the copper from its solution. Chemical reactions involve the transfer of energy, which is associated with the breaking and making of chemical bonds. When bonds are broken, energy must be put in; i.e.
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