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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.
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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This shows they are reliable and can be used as secondary evidence. Another reason why it is a good method of communication is because the results and notes are made during the experiment, this means all the information is correct. There is not bias in this method this is because it only contains the findings that have been found, this makes it a primary result. The second method of scientific communication I will be investigating is newspapers. Newspapers are used to show findings to the public, these findings can be very different to the actual results.
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The stretched molecules suddenly return to their coiled shaped. The film shrinks and wraps tightly around the DVD case Waterproof Clothing: Waterproof clothing is made from Polymers Clothing can be made waterproof by Synthetic Fibre (E.g. Nylon) Nylon stops water getting in, it?s strong so it stops water vapour coming in. The Breathable waterproof clothing has 3 layers, (shown in diagram), Wet outer layer, the middle layer is made of polymer called PTFE and a Dry Inner Layer.
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Ex. ? to prepare lead(ii) sulphate the starting ingredients could be lead(ii) nitrate and sulphuric acid. 2. A precipitate will form immediately. Keep stirring till no more precipitate forms. 3. Using filter paper and a funnel filter to get the salt as the residue since it is insoluble. 4. Wash residue with distilled water to wash off any impurities. 5. Dry this on pieces of filter paper to get the pure salt. III. Method 2 ? Neutralisation 1. Used to prepare soluble salts 2. Used when one of the reagents (can?t be the acid since all acids are soluble)
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Surface filter is a solid sieve, which filters the solid particles without using filter paper. Depth filter is a bed of gritty material, which stops the solid particles from passing through. The surface filter allows the solid particles to be collected intact, unlike the depth filter. Also, the depth filter is less likely to clog than the surface filter. Evaporation is a type of vaporization, vaporization of a liquid but then it occurs on the surface of a liquid or boiling. Evaporation happens when molecules collide and transfer energy to each other at a certain temperature.
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Phosphorus will be determined by precipitation of the insoluble salt magnesium ammonium phosphate hexahydrate according to the reaction: 5H2O(l) + HPO42(aq) + NH4+(aq) + Mg2+(aq) + OH-(aq) → MgNH4PO4 · 6H2O(s) The %P and %P2O5 in the initial sample can be calculated from the mass of MgNH4PO4 · 6H2O(s) obtained using the following method: mass of MgNH4PO4 · 6H2O(s) → moles of MgNH4PO4 · 6H2O(s) → moles of P → mass of P → %P and mass of MgNH4PO4 · 6H2O(s) → moles of MgNH4PO4 · 6H2O(s) → moles of P → moles of P2O5 → mass of P2O5 → %P2O5 In a gravimetric analysis one utilizes a property of certain species that they precipitate (i.e., form an insoluble solid product)
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The stationary phase may be solid, liquid, liquid supported on a solid, or gel. They may be packed in a column, spread as a layer, or distributed as a film. The mobile phase may be gaseous or liquid. In paper chromatography, the filter paper is the stationary phase and the solvent is the mobile phase. The separation is achieved when the solutes in the mobile phase and stationary phase results in different retention lines for the different chemical compounds. The chromatographic system consists of 3 components which are solvents, soluble, and sorbents. Solvents are used to dissolve solutes to form a solution.
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he thought an iron atom would be solid and strong with hooks which would lock it onto another atom. The word atom its self comes from the ancient Greek word atomos meaning indivisible. Democritus believed that all matter could be dived and sub-dived into smaller and smaller units until eventually there would be something that could be divided no more, an atom. This was remarkable as there was no possible way ancient Greeks could support this by observation or experiment. The understanding of atoms did not process much beyond Democritus? theory until the English chemist John Dalton (1766-1844)
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- Boost for the local economy (positive multiplier effect) - Product is used to support many other industries - Tax revenue - Provides valuable resources Disadvantages: - Values of houses decrease - Scares away tourism Social: Advantages - - Noise can potentially be screened - Quarrying can be screened from view E.g by planting a virtual barrier of trees to surround the mining enclosure Disadvantages - - Noise pollution - Dust pollution - Traffic congestion - production of bacteria, germs and insects around which can be harmful for people - affects the weather of the surrounding Environmental: Advantages - - Can be reclaimed as an animal sancturay or a
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Brass is a substitution alloy. It is used for decoration for its bright gold-like appearance; for applications where low friction is required such as locks, gears, bearings, doorknobs, ammunition, and valves; for plumbing and electrical applications; and extensively in musical instruments such as horns and bells for its acoustic properties.
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Davy separated potassium with electrolysis a method now commonly used for experiments in schools and labs. Electrolysis setup The origin of the elements name potassium comes from the Dutch word ?potash?. Its chemical symbol, ?K?, comes from the Arabic word al-qalya, meaning plant-ashes, formed into the Latin word "kalium", most likely because it is an alkali metal (alkali is a group of metals which have similar characteristics e.g. silver colour and soft ________________ Physical Properties ________________ The properties of potassium are that it consists of 19 electrons and 19 protons in its unchanged state with 20 neutrons.
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