Revision notes - origins of life on Earth, chemistry of life
8.4 LIFE ON EARTH 8.4.1 Origin of life 8.4.1.1 Identify the r/ship between the conditions on early Earth and the origin of organic molecules * Early earth contained no ozone layer › large amounts of UV radiation reached the earth * Little free oxygen (anoxic) therefore no ozone layer. * The volcanic emissions filled the atmosphere with methane (CH4), ammonia (NH3), H, CO2, CO and small amounts of water vapour. * The violent electrical storms and acidic rain formed the present warm and mineral-rich oceans. * There are only two possible ways organic molecules could have formed either - formed on earth from simpler molecules (Abiogenesis) - arrived from the cosmos (Panspermia) 8.4.1.2 Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on Earth Panspermia * Elements found in space (H, He, C, O, N, P) can combine to form organic molecules. * Some of these compounds including amino acids have been found in meteors that have struck the earth's surface. * Panspermia proposes that living organisms were seeded on earth as passengers on comets and meteors (ie. Life evolved elsewhere and travelled to earth) 8.4.1.3 Describe two scientific theories relating to the evolution of the chemicals of life and discuss their significance in understanding the origin of life Chemosynthesis * Formation of complex organic molecules on
Internal Resistance of a cell
Topic: Internal Resistance of a cell Aim: To measure the internal resistance and emf (the potential differences across a voltage Source when no current is flowing) and to observe the combination of cells Hypothesis: The emf of the old cell is less than the emf of the new cell but the internal resistance of the old cell is much greater than the new cell. Introduction: Resistance in electricity, property of an electric circuit or part of a circuit that transforms electric energy into heat energy in opposing electric current. Resistance involves collisions of the current-carrying charged particles with fixed particles that make up the structure of the conductors. Resistance is often considered as localized in such devices as lamps, heaters, and resistors, in which it predominates, although it is characteristic of every part of a circuit, including connecting wires and electric transmission lines. (Britannica.2006) The dissipation of electric energy in the form of heat, even though small, affects the amount of electromotive force, or driving voltage, required to produce a given current through the circuit. In fact, the electromotive force V (measured in volts) across a circuit divided by the current I (amperes) through that circuit defines quantitatively the amount of electrical resistance R. Precisely, R = V/I. Thus, if a 12-volt battery steadily drives a 2-ampere
Acid-Base titration by double indicator method
Date: 01/12/2010 Objective To determine the proportions of sodium carbonate and sodium hydroxide in a mixture solution using double indicator method. Procedures . 25 cm3 of the mixture solution was pipetted into a conical flask. 2. Two drops of phenolphthalein indicator were added into the conical flask. 3. The mixture solution was titrated with the given standard hydrochloric acid(0.098M). 4. The mixture was titrated to the end-point. 5. At the end point, the pink colour of phenolphthalein indicator was just discharged. 6. The burette reading (x) was recorded. 7. Two drops of methyl orange and a further quantity of acid were added 8. The mixture was titrated to the end-point. 9. At the end point ,the yellow colour of the methyl orange changed to orange. 0. The reading of that further quantity of acid (y) was recorded. 1. The steps above were repeated 3 times. Results: Volume of piptte used: 25 cm3 The concentration of the hydrochloric acid used: 0.098M x Trial 2 3 Final burette reading / cm3 2.40 31.80 29.40 2.70 Initial burette reading / cm3 0.10 9.50 7.20 0.30 Volume of acid used(x) / cm3 2.30 2.30 2.20 2.40 Mean value of x= (12.30+12.20+12.40)/3 =12.30 cm3 y Trial 2 3 Final burette reading / cm3 9.50 38.80 36.60 9.80 Initial burette reading / cm3 2.40 31.80 29.40 2.70 Volume of acid used(x) / cm3 7.10 7.00
Mitosis and Meiosis, the defining differences.
Mitosis and Meiosis, the defining differences. The cell theory was first proposed by Schleiden in 1838 and Schwann in 1839. This theory was then extended upon by Rudolf Virchow in 1855 declaring that new cells only came from pre-existing cells. Shortly after, in 1887, Weismann suggested a specialist form of division occurred in the manufacture of gametes. These two forms of division are called Mitosis and Meiosis respectively. By definition, Mitosis and Meiosis are very similar, both being methods of cell division. However, the way in which the daughter cell is produced in these processes vary. The biological differences in these two processes lie between Mitosis and Meiosis I, as Meiosis II is almost identical to Mitosis. Mitosis As a consequence of Mitosis, a parent nuclei divides into two daughter nuclei, each with the same number of chromosomes as the parent nucleus. The division of the whole cell follows this. In order to accomplish this chromosome firstly replicate themselves during interphase. The two replicate chromosomes are known as chromatids and separate during mitosis. Cell division is a continuous process with no sharp distinction between the phases. There are 3 main stages: Interphase: this is the episode of synthesis and growth. The cell produces many materials essential for its own growth and for carrying out all its functions. DNA replication occurs
Investigation to determine the Relative atomic mass of Li
Investigation to determine the Relative atomic mass of Li Results and calculations for the first method. Mass of Li used : 0.12g Start volume of Water : 55.5ml Final volume of water : 250.0ml Volume of hydrogen produced : 194.5ml Now based on these results I t is possible to calculate the concentration of the limewater. Calculate the number of moles of hydrogen produced: We have 195ml of hydrogen that has been produced. - This is equal to 0.195 dm3 Since 24dm3 is one mole of hydrogen at room temperature. - 0.195 dm3 = 0.008125 mol Calculate the number of moles of Li reacted: Using the equation: 2Li (s) + 2H2O (l) --> H2 (g) + 2LiOH (aq) 2 : 1 One can see the reacting ratio is 2:1, the no. moles of Li will be twice that of H2. - Moles of Li = 2 x 0.008125 mol - Moles of Li = 0.01625 mol Calculate the relative atomic mass of Li: As the mass of Li and No of moles used are know, it is possible to calculate the relative atomic mass of Li. - Mass of Li = 0.12g - No Moles of Li = 0.01625 mol - Relative atomic mass = mass/no moles - 0.12/0.01625 = 7.3846 - Relative atomic mass of Li = 7.38 Results and calculations for the second titration method. 2 3 End Burette vol (ml) 46.70 43.95 43.70 Start Burette vol (ml) 06.50 01.65 01.30 Amount used (ml) 40.20 42.30 42.40 Using the two best titres (within 0.1 ml),
Nuclear Fusion as energy provider
For ?-decay, unstable atom emits an ?-particle, this can also apply to ?-decay. To distinguish ?-decay and ?-decay, here is a number of characteristic of each of the decay: relative charge, relative mass, nature, range, material to stop, deflection in electric field and magnetic field. ?-emission ?-emission Relative charge +2 -1 Relative mass 4 0.00055 Nature 2 protons + 2 neutrons (Helium nucleus) Electron Range 5cm 6m Material to stop Paper Aluminium(5mm thick)[] Deflection in electric field [2] Slightly towards negative terminal Greatly towards positive terminal Deflection in magnetic field[2] Slightly upwards Greatly downwards As an example, Bismuth can decay into Thallium and Polonium by emitting ?- and ?-particle respectively. For ?-decay of Bismuth: For ?-decay of Bismuth: The example above can show ?-particle is Helium particle while ?-particle is electron. Radioactive decay is different from fission reaction. Radioactive decay Fission . unstable . absorb 1 neutron 2. emit ?/?/?- particle 2. oscillate 3. become other elements 3. unstable 4.Fission (split) 5. give out 3 neutrons Fission reactions differ from radioactive decay both in the way that the reaction must be started and in the type of products that are formed [1]. Radioactive decay is a passive action, while fission is active. For radioactive decay, the atom is unstable;
risks of electricity
WHAT ARE THE RISKS FROM ELECTRICITY? Harm can be caused to any person when they are exposed to 'live parts' that are either touched directly or indirectly by means of some conducting object or material. Voltages over 50 volts AC or 120 volts DC are considered hazardous. Electricity can kill. Each year about 1000 accidents at work involving electric shocks or burns are reported to the Health and Safety Executive (HSE). Around 30 of these are fatal, most of them arising from contact with overhead or underground power cables. WHO IS MOST AT RISK FROM ELECTRICITY? Anyone can be exposed to the dangers of electricity while at work and everyone should be made aware of the dangers. Most electrical accidents occur because individuals: * are working on or near equipment which is thought to be dead but which is, in fact, live * misuse equipment or use electrical equipment which they know to be faulty. LEGAL DUTIES AND OBLIGATIONS AROUND ELECTRICITY As well as a moral duty on employers to protect employees and members of the public, General Health and Safety Legislation covers all employers and workplaces. In addition, specific duties and obligations are laid out in the following regulations: These regulations apply to all aspects of the use of electricity within the workplace from electrical supplies to the use of electrical equipment. They place a duty on employers,
Design two experiments, one using titration and one using gas collection to show that H2SO4 is a dibasic acid.
Chemistry Practical Write-Up Aim: Design two experiments, one using titration and one using gas collection to show that H2SO4 is a dibasic acid. Gas Collection Experiment Prediction: If H2SO4 is dibasic it should give off a volume of hydrogen molecules, equal to the volume of H2SO4 used, below I have calculated how much gas to expect: H2SO4 + Mg › MgSO4 + H2 H2SO4 Concentration: 1 Mol/dm3 Volume: 0.025dm3 Moles: 1x0.025 = 0.025 H2 Moles: 0.025 0.025 * 24 Volume: 0.6dm3 Apparatus: Conical Flask, Magnesium, H2SO4, Bung, delivery tube, bowl of water, measuring cylinder. Diagram: Method: * Setup Apparatus as shown in the diagram. * Fill a conical flash with 25cm3 H2SO4. * Fill the measuring cylinder with water, making sure there are no bubbles, and turn it upside down in the water bath. * Drop the magnesium into the conical flask, and place the quickly place the bung on top. * The hydrogen gas will begin to displace the water in the measuring cylinder, wait until this stops, and record the results in a table like shown below, repeat until you have 3 results and calculate the average amount of gas evolved. Gas(dm3) - 1 Gas(dm3) - 2 Gas(dm³) - 3 Gas Average(dm³) To keep the results accurate we will keep all equipment and solutions used the same every time, we will do this experiment 3 times and take the average of the readings, and use this to see if
Power generation
Introduction: Oil is a liquid fossil fuel and is formed from layers and layers of buried animals and plants that have been under a lot of heat and pressure over a long time. Oil is a non-renewable resource as it cannot be produced on human time frame. Oil is used for many things; it's used for transportation, heating purposes, fuel for electricity generating plants. Fuel is found underground reservoirs. The production of electricity from oil begins with the extraction of oil and ends with the oil burning in boilers and turbines at power plants. Crude oil is removed from the ground by drilling deep wells and pumping it up to the surface. The crude oil is then moved to a refinery (refineries remove a portion of the impurities in the oil, e.g. metals) where it is refined into a number of fuel products: kerosene, gasoline, liquefied petroleum gas (propane). Then this crude oil is moved to power plants by trains, trucks, pipelines or ship. Many methods are used at the power plants to generate electricity from oil. One of the methods is to produce steam by burning the oil in the boilers which is used by a steam turbine to generate electricity. Another common method is to use combustion turbines to burn oil. In a fossil plant, oil, gas or coal is fired in the boiler, which means that the chemical energy of the fuel is converted into heat. Name of Fuel
Effect of nitrate concentration on the growth of Duckweeds
Introduction & Method At the beginning of the experiment, I put on a lab coat to protect myself from any danger that may occur. I made sure that all my equipments were clean and dry before I started, and I also measured the temperature of the room to confirm it was around room temperature. I then made sure that the ice cube tray was clean, I put a little label on one end of the tray to indicate my starting point row of the ice cube tray. I then made a little note to myself that the label indicated the row which will contain the 0.0% x 10-3 concentration of nitrate in the solution, and the rows onwards will contain the concentration of nitrogen in solution in ascending orders which I will use (0.0, 0.4, 0.8, 1.2, 1.6 and 2.4 % x 10-3). I Whilst pouring the solutions into a glass beaker I put on goggles and gloves to protect my eyes and hands from any contacts with the ammonium nitrate solution, as any contact can lead to irritation of the skin and eye. I poured 80-90cm3 of the 1st concentration which contained 0.0% x 10-3 of nitrate into a 100cm3 glass beaker. Next I used a clean syringe to measure out 25cm3 of the solution into the 1st well (near my label). The tray had 3 wells in a row and there were 6 rows, I repeatedly added 25 cm3 of the same ammonium nitrate solution into the remaining two wells of that row, so that I will obtain a result of three replicates with each
