The Periodic Table
The Periodic Table was developed in stages; the first person that attempted to classify elements in relation to their atomic mass was Johann Döbereiner. Döbereiner noticed similar properties between known elements. Theses similarities occurred in groups of threes and were known as 'triads'. The atomic weight of the middle element in each triad is approximately an average of the others. In 1863 John Newlands put the known elements in order of atomic weight and noticed that every eighth element had similar properties, he called this the Law of Octaves. After about 20 elements the table became ragged and some elements had identical places whilst others were incorrect because of inaccurate weights. Furthermore Newlands left no gaps for any unknown elements. Dimitri Mendeleev amended some atomic weight values and left gaps for any undiscovered elements. Mendeleev predicted properties of five elements that should be discovered, within 15 years of his predictions three of these elements had been discovered. One of the unknown elements was called Eka-aluminium today known as Gallium. Below a table compares the predictions made by Mendeleev about gallium with what is now known. Table 1 Comparing Mendeleev's predictions with the properties of element 31, gallium eka-aluminium (Ea) gallium (Ga) atomic weight About 68 69.72 density of solid 6.0g cm-3 5.904g cm-3
Investigatin the Rate of Reaction
Investigating the Rate of Reaction Aim To investigate the effect of concentration on the rate of reaction between sodium thiosulphate and hydrochloric acid. Prediction I predict that as the concentration of the sodium thiosulphate is increased, the rate of reaction will increase. This is because there are more particles, therefore more chances of collisions. The graph that is going to be drawn in my analysis will have a positive correlation. Also it might be curved as the increase in rate of reaction which will not be exactly the same as the concentration of the sodium thiosulphate. This probably will be because there are more chances of collisions. So when the concentration will increase then the particles would have more energy and therefore it will move faster. This is the reason why they will collide more often. Equipment Substances that we're going to use Pipette Hydrochloric acid Stopwatch Sodium thiosulphate Spotting tile Water Conical flask Funnel Burette Method . Set up apparatus as shown in the diagram. 2. Measure 25cm3 of hydrochloric acid and pour into conical flask. 3. Add 25cm3 of 0.2 mol dm-3 of Na2S2O3 to hydrochloric acid and immediately start stopwatch. 4. When the cross disappears stop the stopwatch. 5. Record the results. 6. Repeat steps 1-5 three more times. 7. Repeat step 1-6 for 0.4, 0.6, 0.8, 1.0 mol dm -3 Na2S2O3.
To investigate Dalton’s law of constant composition
Planning of the experiment to investigate Dalton's law of constant composition Dalton in the eighteenth and nineteenth century stated that all pure samples of the same chemical compound contain the same proportions of mass As various copper compounds are readily available for laboratory use, the decision has been made to produce copper from black copper oxide and produce black copper oxide from copper by various methods, and to analysis the findings from this to see that the law of constant composition holds true. No other method or data was found to show or prove Daltons theory was true so the decision to use copper and black copper oxide was the best immediate solution. In the preliminary work, various ways of testing Dalton's theory was researched and tested: * Copper Nitrate (from which copper oxide will be made to make copper) * Copper Hydroxide (from which copper black oxide will be made to make copper) * Copper Carbonate (from which black copper oxide will be made to make copper) * Copper (can be oxidized to form black copper oxide) My variable will be different methods of making black copper oxide, and in my results, I aim to see whether this affects the mass ratio of copper to oxygen in the copper oxide from various methods of creation. Black Copper oxide will have to be reduced using carbon or hydrogen, as they are more reactive than copper and the copper
Find out the theoretical yield of Magnesium Oxide, find the percentage yield of Magnesium Oxide identify any possible errors in the practical.
The Preparation of Magnesium Oxide. Aim: The aim of this coursework is to find out the theoretical yield of Magnesium Oxide, find the percentage yield of Magnesium Oxide identify any possible errors in the practical. Apparatus/ Equipment list: * 1 Crucible with lid. * 10cm Strip of Magnesium strip. * Emery cloth. * Bunsen Burner * Tripod. * Tight Spiral * Heat Proof Mat Risk Assessment: When doing this experiment you must be careful not to hurt yourself. As you can see, the equipment above doesn't seem all that dangerous so not much precaution must be taken when doing this experiment. * Wear Gloves: - You must always wear gloves when doing experiments, but For this experiment its not really necessary so you can wear it Depending on your own choice. * Wear Lab- Coat: - You must always wear a lab coat from the very beginning Of the experiment and this is really necessary, in not Wearing a lab coat you could most probably spill something Onto yourself and this could be highly dangerous. * Wear Safety Goggles: - You must also wear safety goggles at all times they help Help in protecting the eyes from anything in reach with It that is hazardous or dangerous in any form or way. o When Magnesium metal is burnt at high temperatures it emits a very powerful and bright light that is dangerous when looked directly at, so be careful not to look directly into the
Chlorofluorocarbons (CFCs)
Eugine Whint 7/12/2005 Chemistry 5G Chlorofluorocarbons (CFCs) Chlorofluorocarbons (CFCs) (also known as Freon) are non-toxic, non-flammable and non-carcinogenic. They contain fluorine atoms, carbon atoms and chlorine atoms. The 5 main CFCs include CFC-11 (trichlorofluoromethane - CFCl3), CFC-12 (dichloro-difluoromethane - CF2Cl2), CFC-113 (trichloro-trifluoroethane - C2F3Cl3), CFC-114 (dichloro-tetrfluoroethane - C2F4Cl2), and CFC-115 (chloropentafluoroethane - C2F5Cl). CFCs are widely used as coolants in refrigeration and air conditioners, as solvents in cleaners, particularly for electronic circuit boards, as a blowing agents in the production of foam (for example fire extinguishers), and as propellants in aerosols. Indeed, much of the modern lifestyle of the second half of the 20th century had been made possible by the use of CFCs. Man-made CFCs however, are the main cause of stratospheric ozone depletion. CFCs have a lifetime in the atmosphere of about 20 to 100 years, and consequently one free chlorine atom from a CFC molecule can do a lot of damage, destroying ozone molecules for a long time. Although emissions of CFCs around the developed world have largely ceased due to international control agreements, the damage to the stratospheric ozone layer will continue well into the 21st century. -------------------------------------- Chlorofluorocarbons
Decomposition of copper carbonate - proving one of two equations.
AS Chemistry Coursework - Rosalind Brock Winter 2002/3 Decomposition of copper carbonate Aim Copper has two oxides, Cu2O, and CuO. Copper carbonate, CuCO3 decomposes on heating to form one of these oxides and an equation can be written for each possible reaction Equation 1: 2CuCO3 (s) ? Cu2O (s) + 2CO2 (g) + 1/2 O2 (g) Equation 2: CuCO3 (s) ? CuO (s) + CO2 (g) The aim of this experiment is to prove which of these two equations is correct. Background Theory It is possible to determine which equation is correct by measuring the volume of gas given off by the decomposition. This is volumetric analysis. The equation is written in moles. 1 mole of any substance contains the same number of particles as 12g of carbon-12. 1 mole of any element contains 6.01 x 1023 atoms. 1 mole of a molecular compound contains 6.01 x 1023 molecules. This means that in a reaction in which 2 molecules of one substance react with 1 molecule of another - for instance the formation of water: 2H2 + O2 ? 2H2O, 2 moles of hydrogen molecules will react with 1 mole of oxygen molecules to give 2 moles of water molecules. 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
A discussion of Atoms.
Atoms There are 112 elements although elements 110-112 are as yet unnamed. These 112 elements are organized in the periodic table: The modern chemical symbols were introduced by Berzelius. Rows of elements are called "periods" and columns of elements are called "groups" (1A, 2A 3B etc.). There are three general classes of elements distinguished by their physical properties: the metals (generally shiny and conduct electricity), the non metals (not shiny, sometimes gasses at STP and poor conductors of electricity) and the metalloids (properties in between those of metals and non metals.). Some groups have special names: Group 1A: Alkali metals Group 2A: Alkali earth metals Groups 3B-2B: Transition metals Group 7A: Halogens Group 8A: Noble gases Many of the heavier elements are unstable - which means that the atoms of those elements break apart very quickly. Elements within a group share similar chemical properties. Other chemical and physical properties of the elements can be deduced from their position in the periodic table. The structure of the periodic table and thus their chemical and physical properties is directly related to their atomic structure. Atomic Weights Most elements can be found on earth (with the exception of those elements that too unstable and thus must be synthesized in the laboratory). Since all elements have isotopes then we must consider how
Osmosis in potatoes and how various concentrations of salt solution in which potato chips are placed, affect osmosis in the cells.
Biology Coursework: osmosis in potatoes and how various concentrations of salt solution in which potato chips are placed, affect osmosis in the cells. Aim: The aim of this investigation is to see how changing the concentration of salt in a solution will affect osmosis in potatoes. Variables: * The temperature will affect osmosis in cells because the potatoes might cook only a bit and this should cause the tiny paws in the potato to close. * The amount of salt in the concentration will affect the experiment because the greater the amount on the other side, the faster the water moves from ones side to the other. * The surface area of the potato chips is another variable. A larger surface area will be able to absorb more water and there will be more of a permeable surface for the water to move through. * The volume of water is also important. A weaker concentration of salt will affect the rate of reaction because osmosis is the passage of water from a region of high water concentration through a semi permeable membrane to a region of low water concentration. I am going to investigate the concentration of salt. I think that this is the easiest for me to do and I also think that I can get a good set of results from it. My predication: Osmosis is the passage of water from a region of high water concentration through a semi permeable membrane to a region of low water
Does god exist: my opinion?
Does god exist: my opinion? After studying God's existence and the reasons why people think that god does or doesn't exist I have come to the conclusion that I am unsure about his existence. I feel there are some reasons that justify god's existence and other things that don't. I therefore class myself as an agnostic. There are several reasons why I believe that God exists. One idea I have is that because there is so much in the world that is bad I believe there must be something to balance this that is completely good. I believe that God is this. I also think that is each and very person is unique then everyone's life must have a meaning or a purpose and it is God who had given us this. There are many things in life that no matter how hard we try we can not explain. If God exists he provides an answer and explanation to all of these mysteries. This also links in with the idea that life is so complex and diverse many people including myself find it hard to get our heads around the fact the world and everything in is the result of an accident or freak of nature. The fact that the Big Bang just occurred and everything formed is quite a difficult idea to comprehend. Some theories that I feel back up my ideas are Thomas Aquinas' cosmological argument. He states that something can not come from nothing. His argument also says that every effect must have a cause. This makes sense
Periodicity three :Trend in the physical properties of the alkaline earth metals.
Group II - The Alkaline Earth Metals. (Variation in Physical Properties) Beryllium (Be) (Atomic number = 4) s2 2s2 Magnesium (Mg) (Atomic number =12) s2 2s2 2p6 3s2 Calcium (Ca) (atomic number = 20) s2 2s2 2p6 3s2 3p6 4s2 Strontium (Sr) (Atomic number = 38) s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s2 Barium (Ba) (Atomic number = 56) 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s2 Notice that each alkaline earth metal has two electrons in its outermost shell and that these electrons occupy s orbitals. ) Trends in the physical properties of the alkaline earth metals. a) The trend in atomic radius The graph below shows the trend in atomic radius for the alkaline earth metals. Notice that as the atomic number increases the size of the atoms also increase. In other words as group two is descended, atomic radius increases Why is this? Look closely at the electronic structures of each element provided for you at the start of this section. You should see that as you go down the group the number of electron shells increases by one each time (for example the outer shell for beryllium is the second shell and for magnesium it is the third etc) This means that progressively the outer electrons are further from the nucleus and so since atomic radius is the distance from the centre of the atom to the perimeter of the outermost electron shell, the atoms become
