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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
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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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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If acid does touch skin wash it off (immediately). - Don't run in labs, no food or drink. - No concentration of hydrochloric acid greater than 2 molar, anything larger is dangerous. - Clean up any spillages immediately. Equipment list: - Boiling tube = this is where the chemical reaction takes place. - Trough of water = contains the water and fills the beehive unit. - Beehive unit = this increases the surface so that the bubbles can be collected. - Delivery tube = carries the hydrogen bubbles. - Bung = stops the hydrogen bubbles from escaping into the surrounding environment.
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There properties are similar to other metals: there similarities include malleability, ductility, high conductivity of heat and a high conductivity of electricity. The elements act as reducing elements or otherwise "Donors of electrons" meaning they would prefer to give away electrons in the process of electrovalence rather than gain one to become a noble gas the most stable of all elements. What are the differences between the two sets of elements? s The transition metals are like most metals and hence have the same sort of properties.
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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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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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USES: Hearing Aids, watches, pacemakers, calculators Impact on Society * Major impact on society has been the portability of this battery. As the battery is small and has a light weight it has enabled the greater use of electrical appliances in society * Light weight, small size, long life span and stable voltage of a period of time, useful in many small appliances * Silver button cells are increasingly used in medical devices such as pacemakers and hearing aids Environmental Impact * zinc is a heavy metal and in large quantities can have devastating effects.
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Then mark on the underside of the plate four quadrants which can be seen through the translucent jelly. Using a cotton swab, distribute the bacteria throughout the plate, then discard the swab. Then place a label on the cover, which states where each disinfectant will be placed, preventing any confusion. Then get some paper discs and using forceps, place them in the various disinfectants. The place them on the plate and cover and seal the dish. Give the plate to the teacher, which will then incubate the plate at a constant temperature of 20�C for 48 hours.
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So even though we well-planned the procedure and were with good hypothesis and prediction, we could not get better result as we did not use materials accurately. Therefore, to perform the improved experiment and get a better result next time, we have to be more prepared in materials, in planning, in predicting, and in performing the experiment, without having a mistake. Introduction (Jasmine Yu) Acids and bases can be found in everyday household appliances and can be used in many different ways, for instance "the phosphoric acid in Coca-Cola is able to remove rust" (Whitehead, 2008).
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Using the concentration and liters needed during the titration to react the number of moles of unknown can also be calculated. To determine the percent oxalate the end point of the titration is reached and recorded, once the solution has changed color according to the indicator in the an acid/base reaction, or a precipitant is formed in a double , single/ replacement reaction or Redox. Percent by mass can then be determined through stoichiometric calculations using the concentration, moles, liters and molar weight of the known and unknown compounds.
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3. Add about 10cm3 of concentrated hydrochloric acid to the beaker, and cover it with a small watch glass. Place the beaker inside a 250-cm3 beaker which is about 1/3 full of water (refer to the diagram below). Heat this water bath to boiling until a solid material forms in the small beaker. 4. Cool the small beaker in an ice-water bath until the amount of solid formed is constant. 5. Filter off the solid formed by suction filtration, washing any solid from the beaker onto the filter paper. Use a small amount of chilled distilled water for the purpose of washing. 6. Stop suction by lifting the Buchner funnel. Wash the solid with a little chilled distilled water.
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Small, medium, large) of tights The one factor I will be changing in my test is the denier of tights. To make sure my results are dependable, I will repeat the experiment three times for each different type of tights and then work out the average. The apparatus I will need to use to carry out this test are: * Clamp and stand * Newton weights * A weight holder * Ruler * Bulldog clips * Samples of 15 and 40 denier tights Below is a diagram of the apparatus I would use and how I would set up the experiment: It is important that I make sure my experiment and working area is safe.
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Results; Elements Symbol Observations Calcium Ca Flame turned orange red Potassium K Flame turned pink orange Sodium Na Flame turned bright orange Iron Fe Flame immediately turned into orange sparks Copper Cu Flame turned into neon green blue Testing for positive ions: To show the presence of various positive ions. Method; * 1cm3 sodium hydroxide is added to 1cm3 ion solution Results; Positive ion (in solution) Effect of adding sodium hydroxide Calcium This liquid turned into White precipitate. Potassium No reaction occurred.
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Aim: To determine the difference in percentage mass increase when dried spaghetti, is rehydrated for different lights of time. Hypotheses: I hypothesize that if spaghetti is heated for a longer period if time, the mass would increase at 15 grams per minute at a constant rate; because of the heat increases the kinetic energy of the water molecules there for allowing them to have a better chance of collision wit the dry spaghetti. This faster movement of water molecules driven by higher kinetic energy would increase the rate of osmosis.
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Reactivity series: (least) Au, Ag, Cu, Pb, Sn, Fe, Zn, Al, Mg, Ca, Na, K (most) Colour: Certain metals are certain colours. Because of this we could eliminate certain metals that are not that colour. Eg: A metal cannot be Ag (silver) if its colour is gold. pH: Certain metals have a certain pH. We could eliminate certain metals, if, for example, it was alkali. If the metal was alkali (pH 8 - 14) it would be most likely to be a metal from the Group 1 and 2 metals (the alkali metals and the alkali earth metals).
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If they collide, with enough energy then they will react. The minimum amount of kinetic (movement) energy that two particles need if they are going to react when they collide is called the activation energy. There are therefore two main ways of increasing the rate of a reaction: 1) increase the number of collisions 2) increase the amount of movement (kinetic energy) so that more collisions lead to a reaction Low temperature High temperature Reactions occur much more quickly when the surface area of a solid has been increased. When we say "surface area" we mean the amount of solid surface that is available for the reaction.
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Gold is a good conductor of heat and electricity. Most reactants which usually react and form strong bonds don't react with gold. There are some disadvantages of pure gold whatsoever: - Weight - Price - Rarity- gold is usually found as tiny nuggets and most are even too small to see with the naked eye. - It is too malleable - it can be shaped freely by hand, this isn't suitable for jewellery. Another useful property of pure gold is that it is non-toxic and non-irritating when ingested and may be eaten- it is a component of some alcoholic drinks.
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+ 2OH-(aq) � 2H2O(l) + 2e- Cathode: O2(g) + 2H2O(l) + 4e- � 4OH-(aq) . . . . . . (5,11) Figure 6B A Hydrogen-Oxygen Fuel Cell with alkaline electrolyte. Such as is commonly found in space-craft. In both cases the net reaction (for a hydrogen-oxygen fuel cell) is the same as the combustion of Hydrogen. (5,11) (however, since hydrogen never comes in direct contact with oxygen, it is not actually combusted): 2H2(g) + O2(g) � 2H2O(l) (5,11) Applications of the cell The hydrogen-oxygen fuel cell is (in terms of energy sources)
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It is also advised to make the investigation in well-ventilated room to avoid the inhalation. The tongs should be used for carrying the hot crucible, and the special care should be paid while using the Bunsen burner. Procedure of the experiment. To measure the water of crystallisation of salt (CuSO4) I need to measure the mass of hydrated salt, and its mass after dehydration. Therefore I can calculate the mass of water in hydrated salt. Using weight balance I measured the mass of crucible with lid and recorded the date. Then I put the certain amount of CuSO4 to the crucible and recorded its mass.
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The aim of the experiment is to identify 6 unknown colourless liquids by carrying out different chemical reactions on each of the liquids.
Haloalkanes have the general formula of CnH2n+1X where the X represents the halogen. Bromoethane is a primary haloalkane. Carbon1 is attached to two hydrogen atoms and one alkyl group, hence a primary haloalkane. Molecular formula: C2H5Br = CH3CH3Br Structural formula of Bromoethane: Carbon Hydrogen Atoms Bromine Atom Alkyl Group To identify Bromoethane, I will react each of the unidentified liquids with silver nitrate. On reacting, the alkane will form a pale cream precipitate called silver bromide. In a boiling tube, add 10cm3 of dilute alkali solution in ethanol. Then add 5cm3 of the liquid to the boiling tube and place into a waterbath for 5 minutes.
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They have a formula C6H5OH. The Benzene ring makes the OH group more acidic in Phenol than it is in Alcohol. However, Phenols are not as acidic as carboxylic acids. Molecular formula of Phenol: C6H5OH Structural Formula of Phenol: OH group Benzene Ring To test for phenols, the unknown substance will react with bromine water, decolourising the solution and forming a white precipitate.5 Add 5cm3 of the unknown substance into a boiling tube. Then add 2cm3 of Bromine water to the solution and mix well.
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