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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.
- Marked by Teachers essays 10
- Peer Reviewed essays 15
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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The Periodic Table - Revision Notes The numbers in italics are the page numbers of where more information can be found in the revision guide.5 star(s)
The atomic weight tells you the total number of neutrons and protons in the nucleus. Eg 23 Na The atomic number is 11 . The atomic weight (Ar ) is 23. 7 11 Isotopes are two different atoms of the same element that are only different because they have different atomic weights (different numbers of neutrons in their nuclei) Metals and Non-metals 70,71 Most elements are metals . All of the non-metals are in the top right hand corner of the periodic table.
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A long time ago, scientists studied the elements Potassium, Sodium and Lithium and found that they all react alike with water, oxygen and chlorine to produce similar compounds. It had been shown that lithium has a lower rate of reaction than sodium, whereas potassium has a higher rate of reaction than sodium. When you link this with their atomic masses, sodium is yet again the middle element! This same pattern is repeated with other groups of threes, for example: Bromine, Iodine and Chlorine, which eventually became known as the Law of Triads.
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Negatively charged electrons orbited the nucleus. Although Lord Rutherford's model of the atom was essentially the same as today's accepted model, its one flaw was that it proposed that the orbiting electrons would eventually lose energy and spiral in towards the nucleus. > 1913: Neils Bohr, a scientist who had studied with Rutherford, modified the model by suggesting that electrons orbit the nucleus at different energy levels. Only electrons with specific amounts of energy could exist at each level. His model proposed that electrons could move from one level to another by gaining or losing 'packets' of energy.
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This is now a formula. Compounds A material that is made of more than one element joined together is called a compound. In a compound, the atoms are not just mixed, they are chemically bonded together. A compound such as water has particles known as molecules. Elements may join to become compounds and compounds can change to become other compounds. These changes that make new substances are called chemical reactions. Word equations: Hydrogen + oxygen water Reactants "give off" or "change into" Product In water, there are two hydrogen atoms for every oxygen atom.
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How are elements arranged: The Periodic table is a display of all the elements that we know of, it is shaped like a rectangular box. The elements are sorted accordingly depending on their atomic structure, which shows their properties. They are arranged by increasing atomic number, which shows the amount of protons a certain element. Some elements have long names, that is why all elements are given an abbreviation which is shared throughout the scientific world. The atomic number could be found at the bottom left-hand corner of the abbreviation.
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In this essay I will be focussing on two individual scientists and what contribution they made to todays model of the atom, and how having a thorough understanding of the atom has been both an advantage and disadvantage in todays society.4 star(s)
This ray is also known as an 'electron gun'. Thomson constructed his own electron gun and performed experiments on the rays given out of his gun. Through his experiment he found the rays were attracted to a positive charge. Thomson accurately deduced that the rays themselves must be negatively charged because opposites attract and if they were positive then they would repel. He performed additional experiments where he proved that it would take about 2000 electrons to equal the weight of the lightest atom on the periodic table of elements, hydrogen.
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& Si (silicon= 25%) Others: - Aluminium (Al) = 7% - Iron (Fe) = 5% - Sodium (Na) = 5% - Calcium (Ca) = 4% - Magnesium (Mg) = 3% - Nickel (Ni) = 3% - Potassium (K) =2% - Many others Carbon occurs in 2 forms: Diamond (jewelery) Graphite (pencil lead) Is an element. Solid at room temperature 3 legged monster Ring shaped Doesn't conduct electricity Conducts electricity Shines bright/white Dull in appearance (black) Very high melting point Low melting point Very hard Smooth & soft Elements have their own properties: a)
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According to a few unofficial surveys, of the billions of people living in the world, only an extremely small percentage of people have heard of the concept of nanotechnology. As there are two sides to every story there are also two adverse effects and opinions of any scientific discovery or invention. Firstly, I will begin by saying that I believe that nanotechnology is the way forward but only to a certain limit of development as afterwards, in my opinion, scientists attempt to play the role of 'God' or whatever greater force they believe in.
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Pure aluminum, a silvery-white metal, possesses many desirable characteristics. It is light, it is nonmagnetic and nonsparking, stands second among metals in the scale of malleability, and sixth in ductility.In its early days aluminium was too expensive to be used by everybody. It wasn't until a few discoveries in the 1800s that made extraction of aluminium cheaper. As it became easy to extract aluminium from aluminium oxide and extract large amounts of it from bauxite, hence began an era of cheap aluminium.
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The experiment to be conducted will use CaCO3 and HCL to produce => Salt + Water + Carbon Dioxide. Hypothesis: I hypothesize that increasing the concentration of an acid increases the number of collisions between particles, therefore, the rate of reaction increases. The increase will be proportional. PLAN- Variables: Dependent- * the Rate at which CO2 is produced Independent- * Concentration of HCL Controlled- * Volume of HCL * Apparatus * Mass of Marble Chips Apparatus: * 1 x Digital Balance * Paper * 5 x 50ml Beakers * 1 x 150 ml Beaker * 1 x Large Plastic Container
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A poor heat conductor is a good insulator. Conduction works better in solids and gases because the particles are close together. It works better in carpets because carpets contain trapped air because of the feature it contains. Heat energy travels from hotter places to colder places. Heat will transfer between objects that are at the same temperature. Heat travels in solids bye conduction. Metal are good conductors unlike non-metals. Gases are called insulators as they are poor heat conductors. For example bubble wrap is a really good insulator as it contains pockets of air where the heat molecules can get stuck and cannot escape.
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(the molecular mass is found by adding together the relative atomic masses of all the atoms of the molecule) MASS NUMBER, A=NUMBER OF PROTONS+NEUTRONS NUMBER OF NEUTRONS=MASS NUMBER-ATOMIC NUMBER Relative Formula Mass, Mr The relative formula mass is the relative mass of one formula unit of an ionic compound relative to the mass of an atom of carbon 12. (One atom of carbon 12 is given a relative atomic mass of exactly 12). Ions These are atoms which have lost or gained electrons, and are no longer neutral.
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This is called a redox reaction. (Science diagrams) Method 1. Put 1.5g of malachite powder into a large test tube and heat it gently until it turns black and stops rising in the test tube. 2. Allow the tube time to cool 3. Add 1.5g of carbon powder and mix well. 4. Heat the mixture strongly until it turns red and you can see some of the pink copper. 5. Let the mixture cool. 6. Separate the copper from the waste by half filling the test tube with water and pouring the mixture into a beaker of cold water.
- Word count: 644