Kirkcaldy High School - Chemistry N4/ N5 Assignment Pupil Guide. Fuels

Transcription

1 Kirkcaldy High School - Chemistry N4/ N5 Assignment Pupil Guide Name: Class: Fuels This assignment is worth 20% of the overall marks for the National 5 course assessment. The course is graded A-D. It is necessary to complete and pass this assignment in order to gain National 4 Chemistry. In this assignment, you will have to investigate a relevant topic in chemistry and communicate your research in a report. The topic must have an application with an effect on the environment/society. Your report must be completed independently. The assignment has two stages research stage communication stage 1

2 Guidance on Producing your Report Your report should have: Appropriate structure with an informative title and headings where necessary Be clear and concise Aim The aim must describe clearly the question you are trying to answer. Application Here you must describe the application of chemistry and explain its effect on the environment/society. Your explanation must make clear how the application affects the environment/society. This could be a positive or negative effect, or both. Underlying Chemistry Here you should explain how the underlying chemistry relates to your topic. You should include a statement of the chemical principles involved. This may include one or more of: formulae, chemical equations, calculations, a description of properties related to bonding. Research Data/Information Here you must include the data/information from your sources that is relevant to your investigation. This must include data/information that you have processed from at least two of your sources. This can include, for example, performing calculations, plotting graphs from tables, populating a table from other sources, summarising referenced texts, etc. It must be clear where the raw or extracted data/information that you processed came from. For example you could: Include raw data from an experiment/practical activity Include tables, graphs, diagrams, text taken from your sources Explain clearly where the data/information came from (reference your sources) You must present your processed data/information in at least two different formats from: Summary Graph Table Chart (one must be a graph, table chart or diagram) Diagram. Think carefully about the format you choose because it must be suitable for the information you are presenting. Checking that you have included, as appropriate: Suitable scales Units Headings Labels You should also compare the data/information form at least two sources. For example, describe how they agree/disagree or describe other similarities/differences. 2

3 Conclusion You must clearly state the conclusion(s) of your investigation. Your conclusion(s) must relate to your aim and be supported by what you have found out. References At the end of your report you must record the sources you have used, with enough detail to allow someone else to find them. If one of the sources is an experiment/practical activity, then you need to include the title and the aim. You must explain your choice of sources in terms of at least two of the following: Relevance: how useful they are for your topic? Reliability of sources: who wrote them? Who published them? Before submitting your report check you have completed the checklist to ensure you have included everything. Log Book The pages at the end of this booklet should be used to keep track of the tasks you complete during the assignment. You should always put down the date each time you are working on your assignment and then record the information you collect and the source of the information. If this is a website the web address should be noted and if possible the author of the content. If a book or article is used the title and author of the material should be included. Your teacher will check this log regularly to ensure you are using this. It is important you use the log book up to date! If you require more space insert more blank pages and copy the table below onto the page. Should you print anything off be sure the place this in your file and record the information in the table. 3

4 Fuels Fuels A fuel is any substance that can be burned and the heat energy used. We use fuels mainly for heat, electricity generation and transport. Chemists often refer to burning as combustion. Combustion is a reaction with oxygen. The fuels we use are mostly fossil fuels which come from coal, oil and natural gas. All of these are non-renewable it takes millions of years to replace or renew them. They are extracted from the crust of the earth and are formed as a result of the death of prehistoric plants and animals. All of these fuels are hydrocarbon-based i.e. the molecules they contain are made only of the elements hydrogen and carbon. Problems with fuels Burning most fossil fuels releases harmful gases. Some examples are Carbon dioxide (CO2): This is produced as most fuels contain the element carbon. It is thought that carbon dioxide emissions lead to an increased greenhouse effect as carbon dioxide is good at holding heat. This is likely to be causing global warming. Carbon monoxide (CO): This is produced when there is not enough oxygen to completely burn the fuel ( incomplete combustion ). It is a highly toxic gas and is often referred to as the silent killer. Sulphur dioxide (SO2): This is produced in many car engines as a result of sulphur impurities in the fuel. The sulphur reacts with oxygen when the fuel combusts to make sulphur dioxide. Sulphur dioxide can dissolve in water to give sulphuric acid (H2SO4). This can lead to acid rain. Nitrogen dioxide (NO2): This is produced in the engine of petrol cars. The spark in the engine which causes the fuel to combust gives nitrogen in the air enough energy to react with oxygen (nitrogen is usually very unreactive). This leads to nitrogen dioxide which dissolves in water to give nitric acid (HNO3). This can lead to acid rain. The combustion of a hydrocarbon-based fuel can be written as: Fuel + oxygen carbon dioxide + water Our entire economy is based on the price of fuels, particularly oil. It is often said that we live in an oil-based economy. If the price of oil increases then the price of transport, heat and electricity generation increases too. This in turn causes the prices of consumer goods (food, electronics etc.) to increase as well. Alternative Fuels Scientists have been working on new, alternative fuels which could replace fossil fuels. Some possible examples are: Ethanol: produced from the fermentation of sugars Biodiesel: produced from plat oils (which could be waste oil) Hydrogen: produced by the electrolysis of water in a fuel cell. Investigations you could do There are three possible investigations. 1. What fuels could be used to meet our energy requirements? How does the energy released by a fuel depend on the carbon chain length? What are the environmental/social problems with using certain fuels? How does the energy released by alternative fuels compare with the energy released by petrol? 4

5 How could we make better use of finite fossil fuels How are alternative fuels produced? 2. What are the impacts of using ethanol as a fuel? What are the advantages and disadvantages of using ethanol as a fuel? How do the harmful gases released by ethanol compare with those released by other fuels? How is ethanol produced? What are the environmental/social problems with using ethanol as a fuel? 2. What are the impacts of using hydrogen as a fuel? What are the advantages and disadvantages of using hydrogen as a fuel? How do the harmful gases released by hydrogen compare with those released by other fuels? How is hydrogen produced? What are the environmental/social problems with using hydrogen as a fuel? 5

6 Practical This assignment has a practical associate with it. You should write this up separately to your final report but you can include raw and processed data from the practical in your final report. If you do this, you should reference your experiment with the aim and title of the experiment. Practical Carbon Chain Length and Energy Released What is the relationship between energy released by a fuel and the carbon chain length? Apparatus spirit burner (containing fuel) Metal can Beaker thermometer measuring cylinder balance Method 1. Weigh the spirit burner (already containing fuel) with its cap on and record its mass. (The cap should be kept on to cut down the loss of fuel through evaporation) 2. Using the measuring cylinder, measure out 100 cm 3 of water into the beaker. 3. Set up the apparatus as directed by your teacher. 4. Measure and record the temperature of the water. 5. Remove the cap from the spirit burner and immediately light the burner. 6. Slowly and continuously stir the water with the thermometer. When you have heated the water for 3 minutes, recap the spirit burner and measure and record the maximum temperature of the water. 7. Reweigh the spirit burner and record its mass. 8. Use Eh = c m T to calculate the energy released where E = Energy released in kj c = the specific heat capacity of the water (the heat energy needed to raise the temperature of 1 kg of water by 1 C) and has the value 4.18 kj kg -1 C -1. m = the mass (in kg) of water being heated. (The density of water is 1.00 g cm -3 or 1.00 kg l -1 ) T = the rise in temperature in C. 9. Divide Eh by the mass of fuel burnt to calculate the energy released per gramme 6

7 Calculation Example Suppose 0.25 g of fuel had been burned and the temperature of the water had risen by 12.5 C. The heat energy gained by the water (Eh) is calculated using the formula: Eh = c m T E = Energy released in kj c = the specific heat capacity of the water (the heat energy needed to raise the temperature of 1 kg of water by 1 C) and has the value 4.18 kj kg -1 C -1. m = the mass (in kg) of water being heated. (The density of water is 1.00 g cm -3 or 1.00 kg l -1 ) T = the rise in temperature in C. Eh = 4.18 x 0.10 x 12.5 = kj We can now calculate the heat energy released per gram of fuel. Eh (per gramme) = Eh mass of fuel burnt = = kj g -1 (A negative sign is used because this is an exothermic reaction) 7

8 Experiment Log Assessment Standard Evidence required Evidence produced 1.1 Planning an experiment or practical investigation Aim of experiment Dependent and independent variables Variable to be kept constant Measurements and observations are made Resources Method including safety 1.2 Following procedures safely Procedures have been followed safely and correctly 1.3 Making and recording observations and measurements accurately 1.4 Presenting results in an appropriate format 1.5 Drawing valid conclusions Observations and measurements taken are correct Results have been presented in an appropriate format What the experiment shows, with reference to the aim 1.6 Evaluating experimental procedures The suggestion given will improve the experiment 8

9 Aim Application Research worth 10 marks total (includes a mark for the conclusion) Log Final Report Category Sub-category tick describe clearly what you are investigating. Choice of at least 2 sources Selection of data / information Processing information describe the aspect of chemistry being looked at () explain its effect on the environment / society (). (This could be a positive or negative effect, or both.) Give reasons for your choice of sources. Explain why you chose the sources using at least two of the following: 1. Relevance: how useful they are for your topic? 2. Reliability: who wrote or published them? 3. Similar/different perspectives?: do they agree or disagree with each other? show relevant data/information from two, or more, sources. - only one of these can be an experiment. (this can be made in advance and used in the final write up) Make it clear where the data comes from process the data from at least two sources this can include processing data you found into graphs or charts or diagrams (such as converting tables to line graph. table into pie chart or calculate averages from data you found or summarising text that you found Underlying chemistry 3 marks Conclusion Headings and layout References worth 1 mark Clear and concise Presenting information Labelling How the underlying chemistry relates to your topic. Your conclusion(s) relates to aim appropriate informative title The sources of the information you used The information that you processed should be presented in two different formats: Summary Graph One must be a graph, table, chart or Table diagram Chart Diagram Check that you have included, as appropriate: Format 1 Format 2 Suitable scales Units Headings Labels Include the chemical principles involved. Have one or more of Formulae & or chemical equations Other chemistry eg description of properties (related to bonding) ph / homologous series etc calculations Other! Conclusion is supported by what you have found out. Answer your original aim. Headings used where necessary to put your write up into sections / these should be helpful Enough detail to allow someone else to find your original information. If one of the sources is an experiment/practical activity, then you need to include the title and the aim and raw data from the experiment before processing. Information is in your own words, showing you really understood it 9