Doc Brown's Chemistry KS4 science GCSE/IGCSE Revision Notes
A BRAINSTORM on "Rates of Reaction" for chemistry coursework investigations-projects
Ideas for coursework assignments or projects involving the rates or speed of chemical reactions and is a companion page to see also the DETAILED GCSE Revision Notes on the Factors Affecting the Rates of Chemicals which also has brief descriptions of experimental methods and equations, particle pictures and fully explains all the factors affecting the rate of a chemical reaction
Advanced level chemistry theory pages for GCE/AS/A2/IB and adventurous GCSE students!
and A few health and safety ideas on risk assessment
AIM for a high investigation-project mark - you have nothing to lose for your assessment!e.g. suppose you are investigating the effect of hydrochloric acid concentration on the rate at which the acid dissolves limestone (calcium carbonate)
- BUT you can use and extend these 'brain stormed' ideas to most rates of reaction coursework assignments
- The magnesium/zinc + acid reaction, you can investigate acid concentration and amount of metal
- This web page is meant to teach you how to tackle an coursework e.g. on rates, it is not meant to be copied and the details filled in! Your coursework write-up must expressed in your language and expressed at 'your scientific level'.
- Your teacher will have a good idea what to expect and you must be able to justify all your write-up. Use the sources/references mentioned below and clearly indicate them in your write-up.
- More marks are lost by not writing things down, than by not doing experiments! Your write-up must be your work produced from your study and your experiments. This web page is meant to teach you how to tackle an coursework e.g. on rates, it is not meant to be copied and the details filled in!
- Your coursework write-up must expressed in your language and expressed at 'your scientific level'. Your teacher will have a good idea what to expect and you must be able to justify all your write-up.
- Use the sources/references mentioned below and clearly indicate them in your write-up. More marks are lost by not writing things down, than by not doing experiments!
- EMAIL a query or comment on the rates/coursework ideas pagesbut I do NOT do students coursework for them, neither do I replace your teacher supervisor! however I sometimes get really interesting questions and learn something new myself - and that's always a pleasure!
- A BRAINSTORM outline of a whole investigation is outlined below, it is not meant to be prescriptive, but can form the basis of aiming for a high mark and hopefully give you plenty of ideas.
- For sources and references you should research 'rates of reaction' for theory, experimental methods etc. using textbooks, the Internet, and of course your class work and exercise books and mention your research sources in your coursework report AND QUOTE YOUR RESEARCH SOURCES and ANY PREVIOUS 'RATES' EXPERIENCES
- Any previous 'rates of reaction' experience is invaluable and can be used/quoted in your write-up - particularly knowledge of experimental methods which can count as preliminary work.
- Word process your work if you can and your results can be tabulated and processed into graphs using software packages like Excel
- Preliminary work usually involves doing a few trial runs of the experiment to see how it goes and making modifications if necessary. By writing up how, and why, you have changed the experimental conditions or 'recipes' you can gain more marks.
skill P: Planning - the theory and your experiment design!First, you can start by describing the reaction situation you are intending to investigate e.g. with the word and symbol equation, short description about the reaction, and this sets the scene.
- If you are varying temperature, you need to heat up the reactant solutions separately and take their temperatures, mix, start stopwatch. However, they will cool a little standing out in the laboratory, so not completely satisfactory solution to the problem. In the case of the sodium thiosulphate - acid reaction, you can leave the thermometer in the flask and take the temperature at the end, then use an average for the temperature of the reaction.
- If temperature isn't a variable, it must be kept constant. The simplest solution here, is to make sure all the chemicals have been standing in the laboratory prior to the lesson. Then, they will all be at the same temperature, which should be recorded. If more experiments are conducted at another the time, the temperature must again be checked and recorded.
skill O: Obtaining evidence - observations, measurements, in other words the results! (possibly some data you might have been given)
These must be clearly recorded in neat tables showing all the units e.g.
|Run 3: acid concentration ?????, temperature ????|
|Time ????||Gas volume ????||Gas volume ??? (repeat)||corrected gas volume ???|
- You can produce a summary table with the average/corrected (if necessary) gas volumes v time for all the different acid concentrations or whatever variable
- For the hydrochloric acid - sodium thiosulphate reaction you are recording just the reaction time for different thiosulphate or acid concentrations or temperatures, so the data gathering and subsequent processing is 'simpler'.
- All experiments should be repeated where time allows to check for accuracy and consistency, this may become more necessary after you have done a preliminary analysis
- The 'bung effect'! - look up about dead volumes and its correction when dealing with gas volumes!
- Your recorded results should indicate the accuracy of the measuring equipment e.g. 0- 2 decimal places.
- Some of the work done here in presenting the results, e.g. working out averages etc. actually counts towards the mark for analysing (described below).
- Have you got enough results, do they seem ok? Starting the analysis as soon as possible will help you decide whether further, wider ranging or repeat experiments - best decided after examining the graphs of results (see below) - difficult to decide just looking at tables of data.
skill A: Analysing and considering the evidence - what do the results mean in terms of your prediction and theory!The results are initially processed into graphical form ('graphing') for several reasons for both the analysis and evaluating the experimental .... they can clearly show the general trend of the effect of changing that factor or variable, highlighting experimental 'runs' that don't seem to fit the pattern of the other sets of results for the other runs, individual points that don't seem the pattern of a particular sets of results - BUT ITS UP TO YOU
- For the hydrochloric acid - sodium thiosulphate reaction you can plot either (i) reaction time, or (ii) 1/time versus a concentration or temperature (1/time = relative rate of reaction).
- We are basically talking about plotting the initial rate versus e.g. acid concentration.
- If you are doing something like the hydrochloric acid - sodium thiosulphate reaction, your reaction time measures the formation of a fixed amount of sulphur per 'time'. So the rate is 'x amount of sulphur per time', which means the speed or rate is proportional to 1/time, then plot this 1/time against the concentration of the acid.
skill E: Evaluating - and how good are your results then? error sources? can we improve the existing method? are there other experimental methods?Do your results seem consistent and accurate - always refer directly to the graph or graphs in your analysis ... do any of the sets of results not fit in with the others?, do most/all sets of results fit a pattern?, are there any particular points that don't fit the pattern? (anomalies), can some results be ignored in drawing your conclusion(s)? if so, which results and why? QUOTE DIRECTLY - WITH REFERENCE TO YOUR GRAPH(s)
- For the hydrochloric acid - sodium thiosulphate reaction think about the precipitate, observing it etc.
- e.g. in the case of the sodium thiosulphate - hydrochloric acid experiment , you can use a light gate to detect the precipitate formation. The system consists of a light beam emitter and sensor connected to computer and the reaction vessel is placed between the emitter and sensor. The light reading falls as the sulphur precipitate forms.
- Note that if the temperature of a rates experiment was too low compared to all the other experiments, the 'double error' would occur again, but this time the measured gas volume and the calculated speed/rate of reaction would be lower than expected.
This page should help with rates of reaction coursework projects or assignments investigations
Rate of reaction, concentration & temperature
2cm strips of Mg ribbon
Different concentrations of Hydrochloric acid (0.1, 0.5, 1 and 2 molar)
Test tube rack
Place 10ml of the first concentration of acid to be used into a test tube. Place in the thermometer and record the temperature of the acid.
Drop in one of the Mg ribbon strips and start the stopclock.
Observe the reaction, looking for gas being produced. When the reaction stops stop the stopclock. If there is any of the Mg ribbon left this should be noted in an observations column. Note the end temperature.
Repeat this twice more using the same concentration of acid. Repeat the whole process of three tests with each different concentration of acid.
Goggles should be worn throughout the experiment. Spills should be mopped up straight away. Extra care should be taken when handling the most concentrated acid.
The rate of reaction is affected by both concentration and temperature. Does the heating effect of the reaction affect it's rate? How could the above exepriment be adapted to eliminate the heating effect of the reaction and that there may not be enough reactants to complete the reaction?