4742 results found

#### Measuring the e.m.f. And Internal Resistance of a Cell

Measuring the e.m.f. And Internal Resistance of a Cell Planning I wish to find out the electromotive force (e.m.f.) and Internal Resistance of a direct current battery cell. Circuit Diagram . Set up apparatus as shown. 2. Use ammeter to adjust variable resistor to vary of currents. 3. Read voltmeter value and record. 4. Disconnect circuit and take e.m.f reading from voltmeter across cell. 5. Repeat for another 9 resistor settings. Use variable resistor and ammeter to adjust the set up to get a range of 0.1 to 1.0A. 6. Repeat entire experiment to get more accurate average. Safety Aspects . Do not have circuit connected up for too long, this will run the battery down and may cause it to heat up and maybe explode. 2. Wear safety goggles and lab-coats during experiment. 3. Follow standard laboratory safety procedures. Apparatus 0 - 1.0A analogue ammeter 2 digital voltmeters 1 variable resistor 1 cell 8 connecting wires. Safety goggles and lab-coat Paper and pen Arranging Evidence Results Current (Amps) Potential Difference (V) 2 3 Average 0.1 .46 .47 .46 .46 0.2 .42 .42 .41 .42 0.3 .36 .39 .36 .37 0.4 .33 .33 .33 .33 0.5 .27 .29 .28 .28 0.6 .24 .23 .23 .23 0.7 .18 .19 .20 .19 0.8 .13 .15 .14 .14 0.9 .10 .09 .11 .10 .0 .04 .03 .06 .04 Using these results I will be able to draw a graph to find the e.m.f.

• Word count: 1572
• Level: AS and A Level
• Subject: Science

#### How metals react with Acids

HOW METALS REACT WITH ACID AND WATER A) How Metals react with Acids: The reaction of metals with acids starts off by the hydrogen being displaced. Mostly in the reaction a Metal becomes a Cation when it looses one or more valence electrons to bond with the acid and so the Acid becomes an Anion. The Result is an ionic bond, ionic compound. Sodium + Sulphuric Acid --> Sodium Sulphate + Hydrogen After the reaction occurs the result is the compound of the acid and metal used and the reaction would also release Hydrogen. We Might have to balance the equation because of the oxidation state and formulae of the Acid After a Metal and Acid react and substance called salt is made that is an ionic compound made from the neutralisation of a Metal and an Acid Different Metals have different rates of reactions, Metals like Sodium react dangerously Fast Acids like nitric acid have such an oxidation state that makes them react violently with other metals and may cause explosive reactions. Its reaction with a metal does not liberate hydrogen and salt produced usually has a very high oxidised state and heavy corrosion may be the result that is there would be a break down in the properties of the metal reacting with it and nitrogen oxide is produced B) How Metals react with Water: When a metal reacts with water it displaces the hydrogen in the water. Metals react with water more

• Word count: 636
• Level: AS and A Level
• Subject: Science

#### Reactions of the Period 3 elements

Reactions of the Period 3 elements In this essay, I would like to describe the reactions of the Period 3 elements from sodium to argon with water, oxygen and chlorine. Reactions with water For sodium, sodium has a very exothermic reaction with cold water producing hydrogen and a colourless solution of sodium hydroxide. For magnesium, magnesium has a very slight reaction with cold water, but burns in steam. A very clean coil of magnesium dropped into cold water eventually gets covered in small bubbles of hydrogen which float it to the surface. Magnesium hydroxide is formed as a very thin layer on the magnesium and this tends to stop the reaction. Magnesium burns in steam with its typical white flame to produce white magnesium oxide and hydrogen. If you are heating the magnesium in a glass tube, the magnesium also reacts with the glass. That leaves dark grey products (including silicon and perhaps boron from the glass) as well as the white magnesium oxide. The oxide is also produced on heating in steam. Hydroxides are only ever produced using liquid water. For aluminium, aluminium powder heated in steam produces hydrogen and aluminium oxide. The reaction is relatively slow because of the existing strong aluminium oxide layer on the metal, and the build-up of even more oxide during the reaction. For silicon, there is a fair amount of disagreement in the books and on the

• Word count: 955
• Level: AS and A Level
• Subject: Science

#### Finding the concentration of oxalic acid in a mixture with sulphuric acid

The redox titration will be done between potassium permanganate and ethanedioic acid. This reaction requires acid catalyst because ethanedioic acid is too weak an acid to make the solution acidic enough to react at a reasonable rate. Sulphuric acid is in the mixture and provides the acid catalyst. The ethanedioic acid in the mixture will reduce the manganate(VII) ions (MnO4-) into manganese(II) ions (Mn2+). The potassium permanganate will oxidise the oxalic acid into carbon dioxide. H2C2O4(aq) + MnO4-(aq) ? CO2(g) + Mn2+(aq) Reactants Products H2C2O4: Carbon +3 CO2: Carbon +4 MnO4-: Manganese +7 Mn2+: Manganese +2 To work out the ionic equation, balanced electron-half equations for both the potassium permanganate and the ethanedioic acid have to be worked out. Adding electrons (e-), water (H2O) and hydrogen/hydroxide ions (H+/OH-) depending on the conditions, they can be created. Manganate(VII) ions are reduced to form manganese(II) ions. MnO4- + 8H+ + 5e- ? Mn2+ + 4H2O Ethanedioic acid is oxidised to form carbon dioxide. H2C2O4 ? 2CO2 + 2H+ + 2e- The two equations combine and are

• Word count: 1069
• Level: AS and A Level
• Subject: Science

#### "Anorexia Nervosa cannot be satisfactorily accounted for by any single model of abnormality" - discuss

"Anorexia Nervosa cannot be satisfactorily accounted for by any single model of abnormality" Anorexia is a condition disputed by psychologists in attempts to find a cause for the problem. Anorexia is when an individual chooses to emaciate themselves in order to be thin. There are two main types of reasoning behind such behaviour. The biological and psychological explanation. Of course, there are many forms of branched out explanations within these, and the two of which that I shall be exploring are the genetic justification (in terms of biological) and the behaviourist approach, for the psychological relation. Biological psychologists believe that human behaviour and what makes us do what we do, is all down to genes. With the new advance in recent science, genes are becoming a more popular reasoning to many psychological issues. Anorexia nervosa for one. The genetic approach proclaims that the cause for anorexia is to do with genes: i.e. the genetic and inherited factors we have within our relations. The idea is that should one family member suffer from an eating disorder, then there is a higher chance that another family member (preferably those who share the same, or like genes) would contract an eating, or another obsessive-compulsive disorder. Holland et al, a group of psychologists, lead a study on the genetic link of anorexia nervosa in 1984. They perused a sample of

• Word count: 1018
• Level: AS and A Level
• Subject: Science

#### Experiment: Titration Aim My aim is to find the volume of hydrochloric acid needed to neutralise sodium hydroxide.

Experiment: Titration Aim My aim is to find the volume of hydrochloric acid needed to neutralise sodium hydroxide. Theory Titration is a laboratory method used to analyse a chemicals concentration. In this experiment 10cm3 of sodium hydroxide should be neutralised by 10cm3 of hydrochloric acid. Phenolphthalein is used in this experiment as an indictor where the base is a pink colour and acid as a cloudy white colour. When they are use to neutralise each other the mixture goes clear at the endpoint. The endpoint is where the number of moles in both solutions is equal. Different types of titration: * Acid based titration - neutralisation between an acid and a base * Redox titration - form of oxidation reduction * Complexometric titration - used to find certain ions Equipment The equipment I am going to use in this experiment; * Funnel * Hydrochloric acid * Sodium hydroxide * Bosshead / clamp * Stand * Conical flask * Burette * White tile * Goggles * Measuring cylinder * Phenolphthalein Funnel Diagram Bosshead / clamp Burette stand Sodium hydroxide Phenolphthalein White tile measuring cylinder hydrochloric acid Conical flask Method . First I have to collect the equipment, Funnel, hydrochloric acid, sodium hydroxide, bosshead / clamp, stand, conical flask, burette, white tile, goggles, measuring cylinder and

• Word count: 987
• Level: AS and A Level
• Subject: Science

#### I hope to find out how resistance of a wire is affected.

INVESTIGATION TO SHOW THE EFFECTS OF THE RESISTANCE OF A WIRE Aim: - I hope to find out how resistance of a wire is affected. Prediction: - I predict that as the length of the wire increases the resistance will also increase. Scientific Knowledge: - A wire is a bundle of metal strips coated in plastic. The plastic can vary in colour and connect to different terminals These are: - * Black = negative terminal * Red = positive terminal * Blue = neutral terminal * Green and yellow = earth terminal * Brown = live terminal The material varies because it has free electrons, which are able to flow through the wire. The number of the electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be a high number of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase. Resistance is measured in Ohm's (?). Ohm's Law The law actually says that the resistance of a metal conductor is the same whatever the current - unless it's getting hotter. However most people think of these equations when the law gets mentioned: V = IR V is Voltage in Volts, I

• Word count: 581
• Level: AS and A Level
• Subject: Science

#### Parkinsons Disease

Parkinson's Disease (PD) The problem: At the moment there is no cure for PD and treatments still have a long way to go before PD is no longer a major issue. But the real problem is which treatments to use and which path shows the most potential to a full time cure? Introduction: PD normally affects people over the age of 50. It becomes more common with increasing age. 'About 5 in 1,000 people in their 60s and about 40 in 1,000 people in their 80s have PD'1. It affects both men and women but is a little more common in men. PD is not usually inherited, and can affect anyone. However, genetic factors may be important in the small number of people who develop the disease before the age of 50. PD therefore affects a lot of people in the UK and I have chosen this topic so I have a greater understanding of what they go through and how we can help those affected. Background: Biology of Parkinson's disease? Parkinson's disease is a chronic disorder of part of the brain called the substantia nigra. It mainly affects the way the brain co-ordinates the movements of the muscles in various parts of the body. This area of the brain sends messages down nerves in the spinal cord to help control the muscles of the body. Messages are passed between brain cells, nerves and muscles by chemicals called neurotransmitters. Dopamine is the main neurotransmitter that is made by the brain

• Word count: 3857
• Level: AS and A Level
• Subject: Science

#### Should everyone be to taking statins to reduce the risk of cardiovascular disease

Should everyone be to taking statins to reduce the risk of cardiovascular disease? Cardiovascular disease is one of the biggest killers of the modern world. Approximately 70,000 people die from cardiovascular disease or its complications every year in the UK alonei. Worldwide it claims over 17.1 million lives a yearii. Although CVD is a multi-factorial disease with many preventable and non-preventable causes, studies have shown that there is a high correlation between high LDL levels and the incidence of CVDiii. Statins are a group of drugs designed by the pharmatsuitical industry to reduce levels of LDL in one's blood. Low density lipoproteins are protein molecules made up of both triglycerides and cholesterol. Cholesterol is a sterol which means in it insoluble in water. In order for it to pass through the blood stream and diffuse through cell membranes it needs to be attached to a soluble chain molecule such as a triglyceride. Most cardio-vascular events start with the formation of an atheroma, which is an acculmation of fatty deposits in the artery walls between the inside of the artery (lumen) and the elastic muscle layer. An atheroma can lead to the narrow of the lumen in a process called stenosis which increases the patient's blood pressure. The blood constantly hitting the atheroma as it juts out into the lumen can cause it to harden. Often this leads to a

• Word count: 2638
• Level: AS and A Level
• Subject: Science

#### The aim of this experiment is to research on the effect caffeine has on Daphnia heart rate.

THE EFFECTS OF CAFFEINE CONCENTRATION ON DAPHNIA HEART RATE AIM The aim of this experiment is to research on the effect caffeine has on Daphnia heart rate. To enable this, a certain percentage of caffeine solution was tested on Daphnia (water fleas) as it will be a lot easier to monitor their heart rate due to their translucent body. This practical will help develop data representation and improve key practical skills. INTRODUCTION Caffeine is an odourless, slightly bitter alkaloid found in coffee, kola nuts and small amounts of cocoa. In humans, Caffeine acts as a stimulant on the central nervous system preventing drowsiness temporarily in order to keep the brain 'alert'. Caffeine is one of the world's most popularly used drugs and acts a mild diuretic in humans and animals. It will be unethical to carry out this experiment on humans as they have a high level tolerance to caffeine as it was proven in a recent experiment that higher concentrations of caffeine solution causes the heart to beat abnormal fast so an alternative source. Daphnia will be used to carry out this investigation as their resting heart rate is very high and this will air to provide rapid results. .1. Diagram of a typical Daphnia Daphnia are small water crustaceans which share a slight resemblance to water fleas and are mostly found in lakes and ponds. Food sources and beverages containing caffeine

• Word count: 1830
• Level: AS and A Level
• Subject: Science