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GCSE: Patterns of Behaviour
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Measure out 50ml of hydrogen peroxide and pour into a conical flask. Fill a plastic tub, 1/2 full of water. Fill a measuring cylinder to the brim with water. Cover the end of the measuring cylinder making sure no water escapes. Tip the measuring cylinder upside down and place it into the plastic tub of water. Take the rubber bung and tubing. Put the tubing so that the end is inside the measuring cylinder in the water. Put 10 pieces of potato in the hydrogen peroxide. Place the rubber bung in the conical flask as soon as possible.
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A strip of zinc was dipped into the solution and left for 5 minutes. Upon removing the zinc strip a note of the temperature of the solution was taken and the surface of the zinc strip examined, recording any changes that were observed. 3. 1g of zinc powder was carefully weighed on balanced scales and transferred to the copper (II) sulphate solution previously used and stirred while a note of the maximum temperature gained was recorded. 4. The Mixture was then passed through a filter funnel and paper into a chronicle flask and a comparison of the appearance of the filtrate was made with the colour of the original Copper (II)
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For the 1M solution I added 50 cm3 of HCl and 50 cm3 of distilled water, for the 0.5M solution I added 25 cm3 of HCl and 75 cm3 of distilled water. I then measured to see how long it would take to gain 100 cm3 of CO2 using a stopwatch and a gas syringe. To make sure the gas syringe is working properly I must make sure that the clam is not on too tight or it will affect the outcome of the results.
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To investigate the effects of increasing yeast concentration on the rate of Hydrogen Peroxide decomposition
Safety Wear goggles and wash your hands they come nt contact with Hydrogen Peroxide as it is highly irritant. Results Mass of yeast (g) Volume of Oxygen produced (cm3) Time Taken (s) Rate of O2 Production (cm3min-1) 0.0 0 0.00 0.00 0.1 100 103 58.25 0.2 100 36 166.67 0.3 100 17.38 345.22 0.4 100 11.49 522.19 0.5 100 8.2 731.71 Graph Conclusion Hydrogen peroxide decomposes to form oxygen and water; this reaction is catalysed by the enzyme catalase found in yeast. This is shown by the equation below: Catalase H202 O2 + H2O The reason the rate of reaction increases is because the enzyme lowers the level of activation energy required by the reactants in order to react upon collision.
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They have a greater chance of colliding. Because there are more collisions the reaction rate is greater. How does temperature affect the rate of a chemical reaction? When two chemicals react, their molecules have to collide with each other with sufficient energy for the reaction to take place. This is collision theory. The two molecules will only react if they have enough energy. By heating the mixture, you will raise the energy levels of the molecules involved in the reaction. Increasing temperature means the molecules move faster. This is kinetic theory. How do catalysts affect the rate of a reaction?
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Temperature When the temperature of a reaction increases, heat is supplied to the particles of the reactants involved. This heat energy is converted into kinetic energy which all of the particles acquire. This means that more particles collide with each other per second. In addition, the faster the particles are travelling, the greater proportion of them which will have the required minimum energy for reaction to occur, for example, raising the temperature of a reaction by 10�c will double the rate of the reaction. Concentration A chemical reaction will occur only if the particles of the reacting substances are allowed to come into contact.
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Still, Newlands was quite close to the right answer. Newlands' Octaves H Li Ga B C N O F Na Mg Al Si P S Cl K Ca Cr Ti Mn Fe Co,Ni Cu Zn Y In As Se Br Rb Sr Ce,La Zr Di,Mo Ro,Ru Pd Ag Cd U Sn Sb Te I Cs Ba,V Ta W Nb Au Pt,Ir Tl Pb Th Hg Bi Cs The Modern Periodic Table The Modern periodic table is closely based on Mendeleev's table. All the gaps that he left have been filled as more and more new elements were discovered.
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However there were flaws that and one of which was that every 20th element in his table would become disorientated. He had to resort to putting more that element in one place and some elements had been inaccurately measured and placed in the incorrect place. After Newland's attempt The Russian chemist Dmitri Ivanovich Mendeleev (below) produced a better version of the periodic table (left). He became convinced that groups of elements had similar, "periodic" properties. Elements on Mendeleev table were arranged according to their increasing atomic mass, leaving blank spaces where he was sure other, unknown elements would fit.
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Investigating the effect of concentration on the rate of reaction between Sodium thiosulphate and hydrochloric acid
Preliminary work I found that when sodium thiosulphate and hydrochloric acid are mixed the solution turns cloudy white, and then yellow. I found out that it would be best not to stir the solution because this would speed up the reaction and we would not be able to stir it the same each time, so to make it fairer we are not going to stir the solution. We found that the best time to start timing would be from when the last of the acid was poured into the conical flask.
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The reaction gets its energy from the Heat and temperature it is working at, the heat gives the reaction energy, as this energy is given the particles begin to collide, as the temperature increases as does the amount of energy there is to collide with each of the different substances of particles which will collide the fastest. If the temperature is low there would be less energy given to the particles for more collisions per second and the reaction would either not begin or begin very slowly.
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Measure the Hydrochloric acid and take the beaker out of the water bath. Pour the acid into the beaker. As soon as you do this, start the stopwatch. Record how long the reaction takes. Once the 'X' that is marked underneath the beaker is not visible, the reaction has been completed. Repeat this for the temperatures 30?c, 40?c, 50?c and 60?c.
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An investigation to show how we can change the rate of the reaction between magnesium and hydrochloric acid.
Apparatus Hydrochloric acid Magnesium Beaker Ruler Stopwatch Measuring cylinder Method 1. Measure out 50cm3 of hydrochloric acid. 2. Put the 50 cm3 of acid in the beaker. 3. Using a ruler measure 3cm of magnesium. 4. Put the magnesium in the hydrochloric acid starting the stopwatch. 5. Stop the stopwatch when all the magnesium has disappeared. 6. Repeat the experiment using different concentrations. Fair Test In order to ensure that my investigation was a fair test, the following were the kept the same: 1. Always measure 3cm of magnesium before you place it in the beaker which has hydrochloric acid.
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Method: Apparatus list: Sodium Thiosulphate (Na2S2O3) Hydrochloric Acid (HCl) Water (H2O) 1 x Conical Flask 2 x Measuring Cylinder White cardboard marked with black 'X' Stop clock Goggles For this experiment I will use 5 different concentrations of Hydrochloric Acid. They are as follows: Concentration HCl (cm�) H2O (cm�) Na2S2O3 (cm�) 1 5 20 25 2 10 15 25 3 15 10 25 4 20 5 25 5 25 0 25 1. Set up apparatus as above. 2. Measure 25cm� of Sodium Thiosulphate and pour into conical flask.
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Concentration - By increasing the concentration there are more particles what will collide. Stirring - By stirring it will force the particles to collide more which will make a reaction. Equipment Hydrochloric acid (0.25M, 0.5M, 1.0M, 1.25M, 1.5M, 2.0) Sodium Thiosulphate Conical Flask Light Sensors Measuring Cylinder Paper Stop Clock Lamp Bosses Stand Clamps Fair test/ Variables/ Range/ Repeats Fair test - This experiment has to be made fair in order for this to happen certain things have to be done right. The same person in the group has to measure the hydrochloric acid and the sodium thiosulphate.
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By doing any of these in a reaction, increases the chances of the reactants' particles colliding with each other. Investigation Method Here is the first Method I will use to obtain my results in a trial experiment. 1) Use a large measuring cylinder to measure out 40ml of Sodium Thiosulphate into a clean conical flask.
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One of the electrons from the double bonds is put into joining the CH2* part from the radical with one of the CH2 parts from the ethene molecule. The other electron comes from the CH2* part. The other electron from the double bond remains with the second carbon atom and so the product formed is another radical. When ldpe forms, it is branched. This occurs when the growing chain attacks itself and is known as 'back-biting.' | | CH2 CH2 | | -CH2-CH2-CH2* + CH2 -CH2-CH2-CH3 + *CH | | CH2 CH2 | Attack by another radical can then take place at that site which causes the chain to grow out of that radical.
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Method: 1) Set up five test tubes labelled A, B, C, D and E: To tube A add 5 ml buffer pH 12 To tube B add 5 ml buffer pH 9 To tube C add 5 ml buffer pH 7 To tube D add 5 ml buffer pH 4 To tube E add 5 ml buffer pH 1 2) Grind up two soaked peas using a pestle and mortar. These contain the enzyme peroxidase. Add them to tube A using a clean spatula.
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Find out if heating the hydrochloric acid affects the rate of reaction between magnesium and hydrochloric acid.
Measure out 5cm of magnesium ribbon with the ruler and clean as much of magnesium oxide of as possible and, place a rubber tube on the tip of the gas syringe and then drop the 5cm of magnesium ribbon in to the acid and quickly place the bung on it so the gas travels up the tube in the gas syringe. Start timing as soon as it starts to react with the hydrochloric acid. When it has finished reacting, measure how much gas was produced and clear the syringe and then clear the stop watch and repeat this twice with every different temperature.
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Maintaining a high constant body temperature in mammals has both positives and negatives. What are they?
This high metabolic rate aids in the maintenance of the high core temperature, however as most of the heat is generated as a by-product of respiration large therefore vast quantities of food must be consumed. * Herbivores consume plants, which are relatively low in energy and must therefore devote a large portion of their day to eating if they are to maintain this high metabolic rate and internal environment * Carnivores consume food which contain much higher levels of energy and as a result they eat less often In the short term, a change in temperature is detected by the temperature receptors situated in the hypodermis layer of the skin.
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I also think that I will get the most noticeable differences between each experiment. Temperature would be very hard to control, and it wouldn't stay constant - it would get hotter or colder all the time. Surface area would be good to change, but I think that it would be to complicated to work out the exact surface area for each chip, and make sure they're all the same. I am not going to use catalysts because it will be bringing something else into the experiment, and will complicate the whole thing. Collision Theory: The more concentrations, the more collisions.
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Outline the development of the modern Periodic Table, describing how it differs from earlier attempts to classify elements and how the discovery of Gallium supported the Mendeleev's ideas about the Periodic Table.
and the halogen triad (Cl/Br/I). Moseley is another chemist who has aided in the development of the periodic table. He realized that the atomic numbers were not just a convenient numbering scheme for the elements, but had a real physical meaning - ultimately realized as being the number of protons (and electrons) in a (neutral) element. English chemist John Newlands, having arranged the known elements in order of increasing atomic weights, noted that after interval of eight elements similar physical and/or chemical properties reappeared. Newlands was the first to formulate the concept of periodicity in the properties of the chemical elements.
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An example of a primary halogenoalkane would be 1-bromobutane: H�C-CH�-CH�-CH�-Br All of the C-X bonds are polar, the bond enthalpy's for a C-F bond is 467Kj/mol, for a C-Cl bond is 340Kj/mol, for bromine it is 280Kj/mol and for iodine it is 240Kj/mol. These numbers reefer to the amount of energy in kilorjewls taken to break he bonds, I got this information from the AS CHEM WORKBOOK. From this information I know that the Fluorine bond is the most electronegative and the strongest bond and the iodine the least electronegative and therefore the least strong bond as the strength of a bond is determined by its elecronegativity.
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Prediction I predict that when we put less water in the reaction will happen faster this is because the water will slow the reaction down. I also predict that the reaction will happen faster when the solution is at a higher temperature this is because the particles will be moving around quicker causing more collisions. Results Amount (cm�) W 10 St 40 W 15 St 35 W 20 St 30 W 25 St 25 W 30 St 20 W 35 St 15 W 40 St 10 Time (seconds)
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Investigate how the concentration of sodium thiosulphate solution affects the rate of reaction between it and hydrochloric acid.
All four methods of increasing reaction rate can be explained in terms of increasing the number of collisions. Apparatus The equipment I needed was - Varying concentrations of sodium Thiosulphate solution (undiluted concentration at 40 grams/litre) - Hydrochloric acid (2M) - Conical flask - Two measuring cylinders - Piece of paper with a cross drawn on it - Stopwatch - Goggles Here is an illustration of my equipment: Method * Place the flask on top of the paper with a cross marked on it * Mix the following concentrations of sodium thiosulphate by diluting the original (40grams/litre)
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I decided to use different concentrations of HCl in 0.5M, 1.0M, 1.5M and 2.0M (1mole/dm ). To obtain these different concentrations I used a solution of 1.0M which was already prepared and the same with a 2.0M solution. However in order to create a 0.5M and 1.5M solution I had to mix different solutions. The 0.5M solution was made using 10cm of deionised water and 10cm of 1.0M solution, this was then stirred with a glass rod. To make 1.5M solution the same concept was used, I mixed 10cm of 2.0M solution with 10cm of 1.0M solution.
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