Presentation on theme: "IB Criterias chemistry.html tion/2012/10/07/"— Presentation transcript:
IB Criterias chemistry.html tion/2012/10/07/
Data Collection During the experiment all the raw quantitative data, including uncertainties and qualitative observations (where chemically significant) need to be recorded. tigation/2012/09/27/data-collection/ tigation/2012/09/27/data-collection/
DCP Methods for Uncertainty Calculation for Rate (0.10M) KI: Average time is ( ) / 3 = 4.83 s
Uncertainty of time: Uncertainty time = Uncertainty stop watch + reaction time, ( ) = ( 0.10 ) Time = 4.83 ± 0.10 s
% Uncertainty: %Uncertainty time = (0.1/4.83) x100 %=2%
Basic Rules for Propagation
Percent Error Notice that the error is a positive number if the experimental value is too high, and is a negative number if the experimental value is too low.
Graphs all graphs should be presented with: labeled axes. units of measurement and ± uncertainty for each variable (in brackets) an appropriate scale for the data – it should reflect the precision in the data being plotted and where possible the intervals of measurement used an appropriate size (at least ½ page) accurately plotted data points that fill the plot area a key/legend if there are two or more sets of data on the same graph is clear (or series deleted from excel graphs if there is only one set of data) Graphs are called figures and numbered consecutively and the caption is placed under the graph. The title should be concise and incorporates the dependent (y axis) and independent (x axis) variable.
Graphical analysis All graphs need a trend line, that is an appropriate best-fit straight or curved line connecting the points. Plotting scatter graphs with no line or a poorly fitted trend line is not appropriate. – For linear relationships plot an x-y scatter graph (without a line joining the points) and then fit a best fit trend line – For curved relationships plot an x-y scatter graphs (without a line joining the points) and draw a smooth curved line of best fit through the points. The final average result of repeated trials is used for plotting graphs not individual trials.
Error Bars Error bars can be plotted to show the uncertainty associated with the the x or y axis. Typically they are shown for the measured /calculated value / y axis. Error bars can be for fixed values and fixed percentages or customized to reflect different absolute uncertainties for y. Both Excel and Logger Pro can plot error bars