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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.
For an element, the mass of 1 mole is the same as the atomic mass in grams. For a compound the mass of one mole is the same as the relative formula mass or molecular mass in grams. The molecular or formula mass of a compound is found by adding the relative atomic masses of its constituent elements, as found in the periodic table. Substance Mr/Ar - and hence, mass of 1 mole (g) Copper Carbonate (CuCO3) 123.5 Copper Oxide (Cu2O) 143 Copper Oxide (CuO) 79.5 Carbon Dioxide (CO2) 44 Oxygen (O2) 32 So using the equation of a reaction, it is possible to predict the masses of products that will be made by a given mass of reactants.
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Into each tube place equal amounts of the Bromine water (approx. 5 drops in each) and fit the bung. 3. Keep the aluminium wrapped tube in a dark place (e.g. fume cupboard) and the other tube in as light a place a possible; holding by a window is sufficient. 4. After approximately 3 minutes remove the foil and make observations as to the appearance of the two solutions. (One has been exposed to light the other not). Procedure C: Reaction with Acidified Potassium Manganate (VII)
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Mass Of ZnCO3 (g) Mass of ZnO Produced (g) 1 0.648 2 1.296 3 1.944 4 2.592 5 3.24 6 3.888 7 4.536 8 5.184 9 5.832 Here is a graph of the results predicted from the table............ This experiment is going to see how much zinc oxide can be obtained from calamine. It shall also show how close to the conversion can be achieved in practice. Hypothesis In a previous experiment where copper carbonate was obtained from malachite the results showed that as the more malachite was used the more product was produced.
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This led him to propose the Law of Simple Multiple Proportions, which was later verified by the Swedish chemist Berzelius. In an attempt to explain how and why elements would combine with one another in fixed ratios and sometimes also in multiples of those ratios, Dalton formulated his atomic theory. The idea of atoms had been proposed much earlier.
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The aim of this investigation is, to find out which molecules transfer the most energy - investigating fuels
At the start of each reaction, less energy is taken in to break the bonds than is given out at the end of the reaction when new bonds are being made. More energy will be needed to break the bonds apart as we go down the list as there will be more bonds to break. APPARATUS: 1) Thermometer 2) Stopwatch 3) Metal beaker 4) Copper tin 5) 100g water PLAN: 1) Set up apparatus as shown in the diagram 2)
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In this experiment we will measure the density of some liquids and explore some variables. Equipment needed Densities Bottles (labeled with different numbers) Digital balance (to tell us how much the bottle weighed) Glass stoppers 8 liquids ( see data sheets for them) Pipette (to get liquid from bottle to densities bottle) Goggles (incase a chemical splashes into your eye) Lab Coat chemicals we are using to find the density of; Distilled water Ethane-1-2-diol Hydrochloric acid propan-1-ol propan-2-ol Acetone Glycerol Method 1. Take the readings down for the weight off all the bottles you are using for this experiment an example shown below, Mass of relevant density bottle and distilled water = 45.97g density bottle No.
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Aim We are going to carry out a qualitative analysis on our chemicals by flame testing. This process will be carried out by burning an ionic substance into a combustion flame. The results will be recorded by the visual aid of the flame changing colour the test will be carried out on seven unidentified materials. By carrying out the flame test I hope to acquire the skill of flame testing and how to recognised cat ions and anions I also aim to carry this experiment out with a high level of accuracy.
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Describe and explain the type of bonding in ethane, ethene, and benzene. Compare their reactions with bromine.
The two electrons in the pi bond are not always near to the nucleus of the carbon atoms, therefore they do not attract the two atoms as closely, and so the pi bond is weaker than the sigma bond. However the pi and sigma bonds together are stronger than the single sigma bond in ethane and so the C=C bond is shorter and stronger than the C-C bond. As the sigma bond is symmetrical about the axis of the two carbon atoms the carbon atoms are free to rotate about the bond.
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The aim of this investigation is to try and find out the percentage of copper carbonate in malachite.
Other 30-40% of malachite would be carbon di oxide and some impurities. Copper carbonate (heat) Copper oxide + Carbon di oxide + waste gases CuCO3 (heat) CuO + CO2 + waste gases Apparatus: I will use the following equipment for my experiment:- Top-pan balance Pipe-clay triangle Crucible dish Malachite Spatula safety goggles Bunsen burner Heat proof mat Tongs Tripod stand Safety: To keep my experiment safe, I will wear safety goggles to protect my eyes. I will also do my practical quite a distance away from other people and the school equipment (on the practical bench)
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Investigating how the e.m.f. across Opposite Faces of a Piezoelectric Crystal Varies with both Compressive and Tensile Forces
1 x set of masses 2 x wires 2 x crocodile clips 2 x pieces of foil 1 x digital voltmeter (reading to 2 d.p.) Diagram Essentially, this task is composed of two separate experiments - investigating compressive forces, and investigating tensile forces. The two diagrams below use the same apparatus but are adapted slightly for the needs of each experiment. Compressive forces Tensile forces Notes: * The G-Clamp is used to clamp the clamp stand to the table and prevent it from moving.
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The clamp used to fasten the ruler to the table will be sufficiently tight to hold the ruler with no danger of it slipping or moving, (yet not so tight that it could damage the table.) Variables Independent Variable: Mass on ruler Dependent Variable: Depression of ruler I have kept the distance that the ruler is from the edge of the table constant, (95cm is over the edge of the table.) I have not altered the set up of the apparatus throughout the experiment for measuring either the depression for the known masses or the unknown mass.
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For the method we are going to use to see if surface area affects the size of a leaf we are going make sure that we keep the leaves in the same conditions at all time, because light, wind or temperature might affect it. So we are keeping the leaves away from the window and we also will shut the windows, but we can't do much about that so we will presume that the temperature will be kept constant.
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Within this investigation we are going to look at variables that affect how far a certain amount of mass travels when sprung across a smooth surface by an elastic band.
* The thickness of elastic bands was a bad variable to use because I didn't have a wide range of thickness and also there was not a steady increase, there was a wide variety of sizes. * Mass was the best variable to use in my opinion because it gave me a wide variety of results also it was easy to record the results and there was no elements that could make it an unfair test. Prediction I predict that as the mass gets higher the mass will not travel as far.
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These are redox reactions: * The Period 3 element is oxidised * Oxygen is reduced. Metal Oxides Equations for the reactions of oxygen with the metals sodium, magnesium and aluminium are shown below: 4Na (s) + O2 (g) ---> 2Na2O (s) (Vigorous reaction with ignited sodium, ionic sodium oxide formed, yellow flame.) 2Mg (s) + O2 (g) ---> 2MgO (s) (Vigorous reaction with ignited magnesium ionic magnesium chloride formed, white flame.) 4Al (s) + 3O2 (g) ---> 2Al2O3 (s) (Sheets of aluminium get slowly coated with thin oxide layer powdered aluminium shows a vigorous reaction with sparks ionic aluminium oxide formed, white flame.)
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Appearance of Magnesium after experiment: The magnesium turned in a white power form after heated. It contained no smell. Results Mass of crucible + lid =30.44g Mass of crucible + lid + magnesium before heating =30.69g Mass of crucible + lid + magnesium oxide after heating =30.81g The Mass of Each element in the compound Magnesium Mass of crucible + lid + magnesium oxide after heating =30.81g Mass of crucible + lid =30.41g Therefore, the mass of magnesium =0.4g Oxygen Mass of crucible
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I am going to heat up three different metals: 1kg of copper; 1kg of iron and 1kg of aluminum to find compare their rates of heat conductivity
This should increase the accuracy because I will have more useful results because it should show a better curve and it will make it more of a fair test because each metal will be at the same temperature. Fair Test: When conducting this experiment, I plan to place the metals on separate heatproof mats because they are poor conductors and this will reduce heat loss. I will put them on separate heatproof mats so that none of the metals will gain heat from the last experiment on the mat.
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According to 'Practical Chemistry' by Lambert and Muir, the rocks are likely to contain another, similar substance like magnesium carbonate (MgCO3), which will affect the results. Due to this fact that the rocks will contain other, unidentified substances, similar to calcium carbonate, I will need to choose a method that will distinguish between substances and exclude the irrelevant information from the results. For example I will consider limestone, which could contain, among other things, calcium carbonate (CaCO3) and magnesium carbonate (MgCO3).
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These are weak so become easily untangled, this is why they are stretchy. Substances with Covalent bonds are usually non-conductive, and insoluble. They may also dissolve in organic solvents such as ethanol and cyclohexane. I will be using these two solvents along with propanone to test for intermolecular forces. Here is an example of two atoms bonding covalently: Ionic - conduct electricity and when evaporated nothing is left. Ionic with water of crystallisation - conduct electricity and when evaporated a solid is left. Substances with Ionic bonds are usually crystalline solids, therefore usually soluble in water, conduct electricity and are very hard.
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Elements in groups IV and V do not form charged ions. 4. Noble gases do not form chemical bonds. A full outer shell of electrons has extra stability. IONIC BONDING This involves the transfer of electrons from metal atoms to a non-metal atom to form charged ions. The oppositely charged ions are held together by electrostatic attractions.
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To make sure the measuring cylinder gives an accurate measurement read the amount from the bottom of the meniscus on top of the liquid. 2. Record the temperature of this copper sulphate using the thermometer, for maximum accuracy read the thermometer at eye level. 3. Place the empty small beaker on the balance and when it's mass has been measured press the "on" button to put the reading back to zero, this enables the mass of the contents of the glass beaker to be weighed when added with the mass of the glass being included.
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Procedure (1): I will assume that (1) mole of gas occupies 24000cm� at room temperature and pressure. * The number of moles of hydrogen: No. of moles = volume / 24000 = 154 / 24000 = 0.00641667mol = 0.01 mol (2dp) I have used this equation as it indicates that if a gas is kept at equal volumes in the same conditions it contains the same number of molecules. * The number of moles of lithium: The equation above suggests that there is a 2 : 1 ratio. This means that for every (1) mole of hydrogen there are (2)
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Make sure the apparatus is set up behind a safety screen or in a fume cupboard with the front pulled down. 5. Now carefully turn on the gas so it produces a stream of Ethanol. Vapour passing over the oxide. If liquid looks as if it might go over into the reduction tube turn the gas down and if this does not work take the apparatus apart and try to remove more liquid from the wool.
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Triad 1 Triad 2 name atomic mass name atomic mass first element calcium 40.1 lithium 6.9 third element barium 37.3 potassium 39.1 Average mass 88.7 Average mass 23.0 second element strontium 87.6 sodium 23.0 * Newlands - Law of Octaves In 1863 John Newlands, an English chemist, suggested a classification. He arranged the elements in order of their increasing atomic masses. He noted there appeared to be a repetition of similar properties every eighth element. Therefore, he placed seven elements in each group.
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They simply act to speed up the natural process of hydrogen peroxide decomposition. Predictions I predict that the following compounds will be good catalysts: � Manganese IV oxide � Zinc oxide � Iron III oxide � Copper II oxide � Copper I oxide I think this because the above compounds are made up of a transition metal. It is well known that transition metals are good catalysts. Therefore, I also predict that the following compounds will not be good catalysts: � Lead IV oxide � Aluminum oxide Quite obviously, this is because the above compounds do not contain transition metals � Lead is a group IV metal and Aluminum is a group III metal.
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The first could be ionic, where a metal is produced. Ionic bonding involves electrons transferring from one atom to the other consequently leaving an electrostatic force between them. The other form of bonding is covalent where atoms share electrons to complete their outer orbit. An example being Methane where four hydrogen atoms each share an electron with a carbon atom. Hypothesis My hypothesis for this experiment is that as the amount of atoms in the alcohols increase, so will the amount of energy per mole. Prediction I predict that the more bonds there are holding the carbon, oxygen and hydrogen atoms together; more energy will be required to break them apart.
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