61 results found

#### paper cones investigation

Investigation Report Aim Theory When an object is dropped in air, it accelerates. If it is allowed to drop far enough then it can reach its terminal velocity. This is the maximum velocity of the object during its fall and occurs when the upward force of air resistance acting on the object equals the weight of the object. So at terminal velocity... (P.31, Complete Physics, 1999, Pople, Oxford University Press, ISBN 0-19-914734-5) (P.33, Physics 1, 2000, Cambridge University Press, ISBN 0-521-78718-1) Looking for a formula for air resistance... F = force of air resistance ? = density of air = 1.2kgm-3 c = coefficient of drag for the object / dimensionless A = cross-sectional area of object hitting the air / m2 v = velocity of the object / ms-1 (http://damonrinard.com/aero/formulas.htm) Looking for a formula for the weight of an object... W = m.g W = weight / N m = mass / kg g = acceleration due to gravity, 9.81Nkg-1 (P.55, Physics, 1991, Robert Hutchings, Nelson, ISBN 0-17-438510-2) So putting these formulae together... From the Physics AS course, v = velocity x = displacement t = time so References to the specification Forces and Motion 2821 Forces, Fields and Energy 2824 Aim of your investigation The aim of this work is to investigate the relationship between the time taken for a paper cone to fall and the mass of the cone. Variables

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• Word count: 2095
• Level: AS and A Level
• Subject: Science

#### Explain how twin and adoption studies attempt to distinguish genetic and environmental factors underlying the onset of schizophrenia within families. Review the studies and discuss two limitations of this.

Psychology Essay Explain how twin and adoption studies attempt to distinguish genetic and environmental factors underlying the onset of schizophrenia within families. Review the studies and discuss two limitations of this. Schizophrenia is the label applied to a group of disorders characterised by severe personality disorganisation, distortion of reality, and an inability to function in daily life. Symptoms are mainly disturbances of thought processes, but also extend to disturbances of emotion and behaviour. There are two symptom categories - acute schizophrenia characterised by positive symptoms, such as hallucinations and delusions; and chronic schizophrenia, characterised by negative symptoms such as apathy and withdrawal. However, DSM-IV has now moved away from these definitions and classified schizophrenia into three main sub-types: paranoid, disorganised and catatonic. Understanding Schizophrenia More research has, probably, been devoted to trying to understand the nature of schizophrenia than any other mental disorder. Somatogenic approaches have focused on the role of genetic mechanisms influencing the propensity to develop schizophrenia, while psychogenic approaches emphasise the effect of adverse childhood experiences, particularly abnormalities in family interaction in the aetiology of the disorder. Twin studies Twin studies offer a

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• Word count: 1708
• Level: AS and A Level
• Subject: Science

#### Experiment to determine the ethanol content of wine

Experiment to Determine Ethanol Content of Wine The purpose of this experiment is to determine the ethanol content of each of the wines and compare the value determined to the value quoted on the label. These results can then be used to conclude which region is more accurate in quoting the value of the ethanol content of the wine. This experiment takes advantage of the fact that ethanol is less dense than water in solution. The density of ethanol at 20°C is 0.789 g/cm3 while the density of water at the same temperature is 0.998 g/cm3. It then follows that different solutions of ethanol and water will have different densities also, because the relative volume of ethanol increases and water decreases so the density of higher percentage ethanol solutions will be less than the density of lower percentage ethanol solutions. This occurs because water molecules are much smaller than ethanol molecule, meaning more water molecules can "pack" into a smaller volume than ethanol molecules, meaning there is more mass per unit volume of water compared to ethanol, meaning it has a higher density. In this experiment, solutions of ethanol in water were made up, going from 0% to 20%. These were then weighed, and the density of the ethanol was calculated. From this, a graph of percentage ethanol solution against density was made. This graphs later compared to the density of the wine, so

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• Word count: 2599
• Level: AS and A Level
• Subject: Science

#### Relating the structure and function of cell organelles

Relate the structure and function of cell organelles Cells are like cities with intricate organelles 'living and working' in it. There are basically two kinds of cells, namely Prokaryotic and Eukaryotic. Both plant cells and animal cells are eukaryotic while prokaryotic cells are simplier organisms that possess non-membrane bounded organelles. In most cells they contains the following organelles which carry out unique functions and allow cells to work properly. To start off with, nucleus is a large roundish organelle enclosed by a double membrane with numerous openings, namely nuclear pores, for nuclear traffic. It contains chromosomes and one or more nucleoli. Nucleolus is a spherical site where ribosomes are formed. Chromosomes contain DNA which tends to be packed in form of chromatin. Only during interphrase (a stage before a cell divides in a cell division process), chromosomes will be unravelled for easier replication. Tiny, hollow cylinders of protein called centrioles form a network of spindle fibres in the nucleus during nuclear division to pull chromosomes apart. The inner membrane of nucleus will break down and allow chromosomes lying freely in cytoplasm. DNA contains the genetic information and control the synthesis of protein. Each cell contains millions of ribosomes. They are very tiny, non-membrane bounded organelles made of protein and RNA which consist of

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• Word count: 968
• Level: AS and A Level
• Subject: Science

#### Investigate the water potential of celeriac.

Aim Investigate the water potential of celeriac. Apparatus Celeriac - this is the specimen that we will be finding the water potential of. .00 mol dm-3 sucrose solution - this will be placed in the test tube in which the experiment will take place. We will dilute the solution to produce a range of concentrations. 0.0ml Graduated Pipettes (x2) - I had a choice of 5.0ml, 10.0ml and 20.0ml graduated pipettes. I chose this size pipette because it is time efficient and accurate at the same time. It is an accurate piece of equipment because as opposed to standard pipettes, this graduated pipette has 0.1ml graduations to ensure the utmost accuracy. One pipette will be used for water and one will be used for sucrose solution. 250ml Beakers (x2) - these will be used to hold water and the 1.00 mol dm-3 sucrose solution in a safe environment. Cork Borer - this will be used to cut the precise shape of the celeriac. This will also ensure that the surface area to volume ratio is constant throughout the experiment. Razor - this will be used to cut the pieces of celeriac to a precise length. Ruler - this will be used to measure the length of celeriac that will be used in the experiment. Scales - they will be used to measure the mass of celeriac before and after the experiment with accuracy. Therefore, the mass increase/decrease can be calculated after the experiment. These scales

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• Word count: 5310
• Level: AS and A Level
• Subject: Science

#### Preparation of propanone from propan-2-ol

Date: 11/10/2011 Exp. No.: 23 Title: Preparation of propanone from propan-2-ol Aim: The aim of this experiment is to prepare propanone by oxidizing propan-2-ol with acidified potassium dichromate solution. Introduction: Ketones and aldehydes are important series in preparation of other compounds and they are commonly prepared by oxidizing alcohol which is done in this experiment. The experiment is an oxidation reaction where a secondary alcohol (propan-2-ol) is oxidized by acidified potassium dichromate. The reaction does not need to be heated but should be placed in an iced water bath as the reaction is highly exothermic. The product is propanone and no catalyst is needed for the reaction. The propanone is serparated from the reaction mixture by simple distillation and is purified using anhydrous cacium chloride. The equation of this reaction is as follow: Chromic acid is produced in situ by adding potassium dichromate (VI) with sulphuric acid and water. K2Cr2O7 + H2O + 2H2SO4 ? 2 H2CrO4 + 2 NaHSO4 The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. Chromic acid features chromium in an oxidation state of +6. It is a strong and corrosive oxidising agent. Apparatus and chemicals: Apparatus: Quick-fit distillation setup,

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• Word count: 2193
• Level: AS and A Level
• Subject: Science

#### The comparison of antibacterial properties of herbal products and standard antibiotics

The comparison of antibacterial properties of herbal products and standard antibiotics Introduction: This is As biology coursework, studying the area of microbiology the main investigation contains the comparison of antibacterial properties of herbal products and standard antibiotics. Aim: The aim is to investigate the effect of herbal products against standard antibiotics on bacteria growth. To examine the extent to which the herbal products (tea tree oil and peppermint oil) and the standard antibiotics (penicillin and streptomycin), reduce bacteria growth of E.coli and M.luteus. This will be discovered by measuring the growth of bacteria on the agar plates and comparing the results. Background information: The proposed aim surrounds the study of bacteria growth and various other products, which can have an affect on the growth rate; it is therefore necessary to look deeper into the topic criteria to get a wider understanding and to help design an appropriate hypothesis. From self-knowledge antibiotics are chemicals produced by microorganisms, which are designed to inhibit and destroy specific pathogens when used at low temperatures. Antibiotics release chemicals, which inhibit bacterial growth and work on a specific action site. The first founded antibiotic was penicillin discovered accidentally by Alexander Fleming in 1928 from a mold culture. It can be

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• Level: AS and A Level
• Subject: Science

#### Write an essay on electrode potentials.

F7 Essay Writing (Electrode Potentials) Q. Write an essay on electrode potentials. Outlines: (I) What are electrode potentials? (a) associated with equilibria of redox systems (half cells): e.g. metal / metal ion system ; non-metal / ion system ; ion / ion system; (b) reactivity, tendency for reduction to occur (losing electrons) and potential difference; (c) the potential difference of a half cell cannot be measured alone, but a relative value could be measured with another reference half cell / reference electrode; (d) a standard hydrogen electrode [SHE] (in which the emf is defined as zero) is used as the reference electrode; (II) How are electrode potentials measured? (a) concentration, temperature and pressure affect the emf of SHE, and the standard electrode potentials are obtained under conditions of 298K, 1 atm and conc. of 1M. (b) set up a cell with SHE and a salt bridge of electrolyte (e.g. KNO3); (c) a potentiometer is used to measure the cell emf (maximum potential difference), and the sign of cell emf = polarity of the right hand electrode. (III) How are electrode potentials used? / Application of electrode potentials? (a) calculation of cell emf ; (b) prediction of reaction feasibility and limitations. ~ Sample Essay ~ An electrode potential is the difference in an potential between an electrode and its surrounding electrolyte. It is

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• Word count: 1107
• Level: AS and A Level
• Subject: Science

#### Experiment to Determine Acidities of Wine. The purpose of this experiment is to determine the total and volatile acidities of each of the wines and compare them.

Experiment to Determine Acidities of Wine The purpose of this experiment is to determine the total and volatile acidities of each of the wines and compare them. Acidity is a major contributor to the taste of wines. This is especially important in white wines, because there are very little tannins found in it, so acidity can affect the taste of the wine much more than in red wines. In this experiment, 0.1M Sodium Hydroxide solution is needed for titrations. Because this is not a standard solution, it is first standardised using oxalic acid. In order to calculate the total acidity of the wine, a titration with 0.1M sodium hydroxide is carried out with a pH meter. The pH of the wine and sodium hydroxide solution is measured when a certain volume of NaOH is added each time, and a titration curve of volume against pH is plotted. The volume for the solution to reach a pH of 8.2 is recorded. This is because NaOH is a strong alkali and wine is a weak acid, so the pH lies more to the side of the alkali. A pH of 8.2 as the equivalence point is a value agreed on by winemakers. In order to calculate the total acidity of the wine, a representative acid must be used. This must be chosen because wine contains multiple different acids, which require different moles of NaOH to neutralise them. Tartaric acid was chosen as the representative acid for the wine, because it is thought to

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• Level: AS and A Level
• Subject: Science

#### The effect of drugs on the nervous system

The effect of drugs on the nervous system A drug is defined as a substance that, when absorbed into the body, alters a normal bodily function. Some are able to do this, as they are capable of producing an array of different effects on the nervous system. The reason why affecting the nervous system of an organism is potentially so significant is due to the nature of it. The fact the nervous system directs the functions of all the tissues of the body demonstrates its considerable role within the body. It can therefore be assumed that taking substances which affect how it works may lead to a distortion in the way your body is run, producing unsafe side effects. The term nervous system is actually used to describe two divisions. The central nervous system (CNS) is the part which contains the brain and spinal cord. The peripheral nervous system (PNS) however, consists of all the sensory neurones used to detect stimuli. The PNS receives thousands of sensory inputs and transmits them to the brain via the spinal cord. The brain will then process this information, discarding around 99% of it as unimportant. After this sensory information has been processed, areas of the nervous system generate nerve impulses to organs or tissue and form a suitable response. As influences from chemicals are able to affect how the nervous system functions, it can be assumed that chemicals such as

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• Word count: 923
• Level: AS and A Level
• Subject: Science